rate of reaction Archives

Explain the effect of concentration on the rate of reaction?

December 1, 2020 by Veerendra

Explain the effect of concentration on the rate of reaction?

Effect of concentration on the rate of reaction:

When the concentration of a reactant increases, the rate of reaction also increases.
(a) For example, two sets of experiments are carried out using the reacting conditions below:
Set I: 1 g of zinc powder and 20 cm³ of 0.4 mol dm^–³ hydrochloric acid at room temperature.
Set II: 1 g of zinc powder and 20 cm³ of 2 mol dm^–³ hydrochloric acid at room temperature.
(b) The rate of reaction of set I is higher than that of set II.
(c) This is because the concentration of hydrochloric acid used in set I is higher than that in set II.
When investigating experimentally the effect of concentration on the rate of reaction,
- the experiment is repeated a few times, each time using a different concentration of a reactant
- all the other factors/conditions are kept constant in all the experiments.

Other suitable reactions to study the effect of concentration on the rate of reaction.

The effect of concentration of a dilute acid on the rate of reaction involving the liberation of a gas such as the reaction between a reactive metal (Mg/Al/Zn/Fe) and a dilute acid (HCl/H₂SO₄) to liberate hydrogen gas, a carbonate salt and a dilute acid to liberate carbon dioxide gas can also be investigated experimentally.
- The experiment is carried out twice by changing the concentration of the dilute acid.
- The curves for the volume of gas liberated against time for both sets of the experiments are plotted on the same axes.
- The gradients of the curves are compared to deduce the difference in rates.
Different shapes of curves may be obtained depending on the volume and concentration of the dilute acid used.

Table illustrates some examples.
Explain the effect of concentration on the rate of reaction 1

People also ask

How does concentration affect the rate of reaction experiment

Aim: To investigate the effect of concentration on the rate of reaction.
Problem statement: How does the concentration of a reactant affect the rate of reaction?
Hypothesis: When the concentration of a reactant increases, the rate of reaction becomes higher.
Variables:
(a) Manipulated variable : Concentration of sodium thiosulphate solution
(b) Responding variable : Rate of reaction
(c) Controlled variables : Temperature, total volume of the reacting mixture, concentration and volume of sulphuric acid, size of conical flask
Operational definition:
Rate of reaction is inversely proportional to the time taken for the mark ‘X’ to disappear from sight.
Explain the effect of concentration on the rate of reaction 3
Materials: 0.2 mol dm^–³ sodium thiosulphate solution, 1.0 mol dm^–³ sulphuric acid, distilled water, white paper with a mark ‘X’ at the centre.
Apparatus: 150 cm³ conical flasks, 50 cm³ measuring cylinder, 10 cm³ measuring cylinder, digital stopwatch (electronically operated with an accuracy of 0.01 s).
Procedure:

45 cm³ of 0.2 mol dm^–³ sodium thiosulphate solution is measured using a 50 cm³ measuring cylinder and poured into a conical flask.
The conical flask is placed on top of a piece of white paper with a mark ‘X’ at the centre.
5 cm³ of 1.0 mol dm^–³ sulphuric acid is measured using a 10 cm³ measuring cylinder.
The sulphuric acid is then poured quickly and carefully into the conical flask and a stopwatch is started immediately.
The mixture in the conical flask is swirled a few times. The conical flask is then placed back on the white paper.
The mark ‘X’ is viewed vertically from the top through the solution, as shown in Figure.
The stopwatch is stopped immediately once the mark ‘X’ disappears from sight.
The time t required for the mark ‘X’ to disappear from sight is recorded.
The experiment is repeated four more times using different volumes of 0.2 mol dm^–³ sodium thiosulphate solution diluted with different volumes of distilled water, as shown in Table.
The results are recorded.

Results:
Explain the effect of concentration on the rate of reaction 5

Interpreting data:
Based on the results obtained, two graphs are plotted.
(a) Graph I: Graph of the concentration of sodium thiosulphate solution against time, as shown in figure.
(b) Graph II: Graph of the concentration of sodium thiosulphate solution against 1/time, as shown in figure.
Explain the effect of concentration on the rate of reaction 7

Discussion:

Sodium thiosulphate solution reacts with dilute sulphuric acid at a very low rate to form a yellow precipitate of sulphur. The chemical equation for the reaction is:
In this experiment, the time taken for the formation of a fixed quantity of sulphur to cover the mark ‘X’ until it disappears from sight can be used to measure the rate of reaction.
(a) Based on graph I, it can be seen that as the concentration of sodium thiosulphate solution decreases, a longer time is needed for mark ‘X’ to disappear from sight.
(b) Hence, it infers that as the concentration of sodium thiosulphate solution becomes lower, the rate of reaction also decreases.
(a) Graph II is a straight line. Thus, it implies that the concentration of sodium thiosulphate solution is directly proportional to 1/time.
(b) Since rate of reaction is directly proportional to 1/time, it can be deduced that:
Rate of reaction is directly proportional to the concentration of sodium thiosulphate solution.
(c) In other words:
When the concentration of a reactant increases, the rate of reaction becomes higher.
(a) In this experiment, conical flasks of the same shape and size are used.
(b) If the 150 cm³ conical flasks are replaced by bigger 250 cm³ conical flasks, the time taken for the mark ‘X’ to disappear from sight becomes longer.
(c) This is because the base area of the 250 cm³ conical flask is bigger and the depth of the 50 cm³ solution becomes shallower. Hence, a bigger amount of sulphur precipitate is required to cause the mark ‘X’ to disappear from sight.
(a) in this experiment, if hydrochloric acid of the same concentration is used to replace sulphuric acid, the rate of reaction will become lower.
(b) This is because hydrochloric acid is a strong monoprotic acid, whereas sulphuric acid is a strong diprotic acid. Hence, the concentration of hydrogen ions in hydrochloric acid is only half the concentration of hydrogen ions in sulphuric acid.
Total volume of the reacting mixture in all the five sets of the experiments are the same, that is, 50 cm³. This is to ensure that the quantity of sulphur required for the mark ‘X’ to disappear from sight is the same for all the five sets of the experiments.

Conclusion:
When the concentration of a reactant increases, the rate of reaction also increases. Hence, the hypothesis can be accepted.

What is the effect of a catalyst on the rate of a reaction?

December 1, 2020 by Veerendra

What is the effect of a catalyst on the rate of a reaction?

Effect of catalyst on the rate of reaction:

A catalyst is a substance which can alter the rate of a chemical reaction while itself remains chemically unchanged at the end of the reaction.
(a) Catalysts can be classified into positive catalysts and negative catalysts (inhibitors).
(b) A positive catalystis a catalyst that increases the rate of a reaction.
(c) A negative catalyst is a catalyst that decreases the rate of a reaction.

Table shows a few examples of catalysed reactions.

Type of reaction	Catalyst used	Effect of catalyst on the rate of reaction
Reaction between zinc and sulphuric acid Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)	Copper(II) sulphate solution	Rate of reaction increases. (Positive catalyst)
Decomposition of hydrogen peroxide solution 2H₂O₂(aq) → 2H₂O(I) + O₂(g)	Manganese(IV) oxide/ lead(II) oxide	Rate of reaction increases. (Positive catalyst)
Decomposition of sodium chlorate(l) solution 2NaOCl(aq) → 2NaCl(aq) + O₂(g)	Manganese(IV) oxide	Rate of reaction increases. (Positive catalyst)
Decomposition of hydrogen peroxide solution 2H₂O₂(aq) → 2H₂O(l) + O₂(g)	Propane-1,2,3-triol (glycerine)	Rate of reaction decreases. (Negative catalyst)

A catalyst does not change the quantity of the products formed. It only alters the rate of the reaction.
An example of the effect of catalyst on the rate of reaction is shown in table.

What is the effect of a catalyst on the rate of a reaction 1

People also ask

Characteristics of catalysts:
Catalysts exhibit the following characteristics:

Catalyst remains chemically unchanged at the end of a reaction. It means that the quantity and chemical composition of the catalyst remain unchanged at the end of the reaction.
Catalyst alters the rate of a chemical reaction. Positive catalyst increases the rate of reaction. Negative catalyst decreases the rate of reaction.
Catalyst does not change the quantity of products formed. The amount of products remains the same with or without the catalyst.
Catalyst is specific in its action. It can only catalyse a particular reaction but not other reactions.
Only a small amount of catalyst is needed to achieve a big increase in the rate of reaction.
An increase in the amount of catalyst used will cause only a very slight increase in the rate of reacton. Hence, it is not necessary to use a large amount of catalyst in a reaction.
Finely divided (powdered) catalyst is more effective than lump catalyst.
Catalyst used can be in the solid, liquid, gas or aqueous state. A solid catalyst may undergo physical changes. For example, crystals may turn into powder during the reaction.

Most catalysts are transition elements or compounds of transition elements such as iron, platinum, nickel, vanadium(V) oxide, copper(II) sulphate and manganese(IV) oxide.

Effect of pressure on the rate of‘reaction

For reactions with reactants in the form of solid, liquid and aqueous solution, the rates of the reactions do not depend on the pressure.
Only for those reactions that involve gaseous reactants, the rates of the reactions will increase when the pressure increases or vice versa.
An example is illustrated by the combustion of petrol in the car engine as explained below:
- Petrol is a liquid mixture of hydrocarbons.
- In the car engine, the mixture of petrol vapour and air is compressed to a high pressure so that the mixture can be ignited rapidly by the spark plug.
- The high pressure results in a high rate of combustion of petrol.

Effect of catalyst on rate of reaction experiment 1

Aim: To investigate the effect of catalyst on the rate of reaction.
Problem statement: How does a catalyst affect the rate of reaction?
Hypothesis: The presence of a catalyst will increase the rate of reaction.
Variables:
(a) Manipulated variable : Presence or absence of a catalyst
(b) Responding variable : Rate of reaction
(c) Controlled variables : Volume and concentration of hydrogen peroxide solution, temperature
Operational definition:
The decomposition of hydrogen peroxide is fast if the wooden splint rekindles brightly and rapidly. The decomposition of hydrogen peroxide is slow if the wooden splint glows dimly and slowly.
Materials: 20-volume hydrogen peroxide solution, manganese(IV) oxide powder, filter paper, wooden splints.
Apparatus: Test tubes, retort stands and clamps, 10 cm³ measuring cylinder, filter funnel, 150 cm³ beaker, spatula, electronic balance.
Procedure:

Two test tubes are labelled I and II respectively.
5 cm³ of 20-volume hydrogen peroxide solution is measured and poured separately into test tubes I and II respectively.
1.0 g of manganese(IV) oxide powder is weighed and added to the solution in test tube II.
A glowing wooden splinter is immediately brought to the mouth of each of the test tubes.
The changes that occur are recorded in a table.
At the end of the reaction, the mixture in test tube II is filtered to separate the manganese(IV) oxide powder.
The manganese(IV) oxide powder obtained is washed with a little distilled water and pressed between sheets of filter paper.
The dry manganese(IV) oxide powder is weighed and its mass is recorded.

Results:

Test tube	Observation
I	The wooden splint glows dimly and slowly. No effervescence occurs.
II	The wooden splint rekindles brightly and rapidly. Effervescence occurs.

Mass of manganese(IV) oxide before reaction = 1.0 g
Mass of manganese(IV) oxide after reaction = 1.0 g

Inferences:

Rate of decomposition of hydrogen peroxide increases in the presence of manganese(IV) oxide powder.
Mass of manganese(IV) oxide powder remains unchanged during the reaction.
Manganese(IV) oxide acts as a catalyst.

Discussion:

(a) Oxygen gas is liberated during the decomposition of hydrogen peroxide.
2H₂O₂(aq) → 2H₂O(l) + O₂(g)
(b) The liberation of oxygen gas can be confirmed if the wooden splint rekindles brightly or continues to glow.
Manganese(IV) oxide acts as a (positive) catalyst to increase the rate of decomposition of hydrogen peroxide while itself remains chemically unchanged at the end of the reaction. Hence, its mass remains unchanged at the end of the reaction.

Conclusion:
The presence of a (positive) catalyst increases the rate of a reaction. Hence, the hypothesis can be accepted.

Effect of catalyst on rate of reaction experiment 2

Aim: To investigate the effect of the amount of catalyst on the rate of reaction.
Problem statement: How does the amount of a catalyst affect the rate of a reaction?
Hypothesis: When the amount of a catalyst used increases, the rate of reaction also increases.
Variables:
(a) Manipulated variable : Amount/mass of catalyst
(b) Responding variable : Rate of reaction
(c) Controlled variables : Temperature, volume and concentration of hydrogen peroxide solution
Operational definition:
The curve for the graph of volume of gas liberated against time with a higher gradient indicates a higher rate of reaction.
Materials: 2-volume hydrogen peroxide solution, manganese(IV) oxide powder.
Apparatus: 50 cm³ measuring cylinder, 150 cm³ conical flask, stopper fitted with a delivery tube, burette, retort stand and clamp, basin, electronic balance, stopwatch, spatula, beaker.
Procedure:

A burette is filled with water until it is full. The burette is inverted over water in a basin and clamped vertically using a retort stand.
The water level in the burette is adjusted and the initial burette reading is recorded.
50 cm³ of 2-volume hydrogen peroxide solution is measured using a measuring cylinder and poured into a conical flask.
0.2 g of manganese(IV) oxide powder is weighed using an electronic balance and poured carefully into the conical flask.
The conical flask is then closed immediately with a stopper fitted with a delivery tube directed to the burette, as shown in Figure. At the same time, a stopwatch is started immediately.
The conical flask with its contents is shaken slowly and the volume of oxygen gas collected in the burette is recorded at regular time intervals of 30 seconds for 5 minutes.
Steps 1 to 6 are repeated using 0.8 g of manganese(IV) oxide powder to replace the 0.2 g of manganese(IV) oxide powder.
The results are tabulated.

Results:
Set I: Using 0.2 g of manganese(IV) oxide powder
What is the effect of a catalyst on the rate of a reaction 4
Set II: Using 0.8 g of manganese(IV) oxide powder

Interpreting data:

Based on the results obtained, the graphs of the volume of oxygen gas liberated against time for both sets I and II are plotted on the same axes.
Based on the graphs plotted, the following inferences can be made.
- Curve I has a lower gradient, thus lower rate of reaction.
- Curve Il has a higher gradient, thus higher rate of reaction.

Discussion:

The amount of manganese(IV) oxide powder (catalyst) used in set II is four times the amount of manganese(IV) oxide powder used in set I.
Based on the inferences made, it can be deduced that:
As the amount of manganese(IV) oxide powder (catalyst) used increases, the rate of reaction also increases.
There is only a very slight increase in the rate of reaction when using 4 times more manganese(IV) oxide powder as a catalyst.
(a) If the reaction is allowed to proceed until all the hydrogen peroxide is completely decomposed, the graphs in Figure will be obtained.

(b) (i) The graphs show that the maximum volume of oxygen gas liberated in both sets I and II are the same, that is, V cm³.
(ii) This is because the quantities of hydrogen peroxide solution used, in mole, in both sets I and II are the same.
(iii) The manganese(IV) oxide powder as a catalyst does not affect the amount of products formed.

Conclusion:
An increase in the amount of catalyst used will increase the rate of reaction. Hence, the hypothesis can be accepted.
Note: There is only a very slight increase in the rate of reaction when the amount of catalyst increases.

How do you calculate the reaction rate?

December 1, 2020December 1, 2020 by Veerendra

How do you calculate the reaction rate?

Methods to measure the rate of reaction

The rate of reaction can be measured in two ways:
(a) Average rate of reaction
(b) Rate of reaction at a given time
The average rate of reaction is the average value of the rate of reaction within a specified period of time.
Example: 0.2 g of a magnesium ribbon reacts completely with dilute hydrochloric acid in 40 seconds. What is the rate of reaction?
Solution:
(a) The rate of reaction determined in above Example is known as the average rate of reaction.
(b) This is because it gives the average value of the rate of reaction within the 40 seconds.
The average rate of reaction does not show the actual rate of reaction at a particular instant. Only the rate of reaction at a given time can be used to reflect the actual rate at that instant.
Definition:
The rate of reaction at a given time is the actual rate of reaction at that instant.
The rate of reaction at a given time is also known as the instantaneous rate of reaction.

People also ask

Calculating the rate of reaction for a reaction that liberates a gas:

For a reaction involving the liberation of a gas, the rate of reaction can be determined through the following ways.

An experiment is carried out to measure the volume of gas collected at regular time intervals.
A graph of the volume of gas collected against time is plotted.
The graph plotted has the shape as shown in Figure.
The graph can be used to determine the average rate of reaction and rate of reaction at a given time.

Determining the average rate of reaction from the graph:
How do you calculate the reaction rate 3
From Figure,
the average rate of reaction in the first t₁, second

Determining the rate of reaction at a given time from the graph:
How do you calculate the reaction rate 5
From Figure,
the gradient of the tangent at any point on the curve

This is the rate of reaction at that given time.
Hence,
Rate of reaction at a given time = gradient of the curve at that instant
The rate of reaction at a given time, t, can be calculated through the following steps.
Step 1: Draw a tangent (line AB) on the curve at the time t.
Step 2: Draw the right-angled triangle ABC.
Step 3: Measure the lengths of AC and BC.
Step 4: Calculate the gradient of the tangent AB.
Rate of reaction at time t
= gradient of the curve at time t
= gradient of the tangent AB
How do you calculate the reaction rate 7

Shapes of curves using different selected quantities to measure the rate of reaction
Assuming a reaction is represented by the following equation:
R + T → W + X
The following changes occur as the reaction proceeds:

Mass or concentration of the reactants R and T decreases with time.
Mass or concentration of the products W and X increases with time.

For example, a reaction is carried out by mixing excess marble with dilute nitric acid. The chemical equation for the reaction is represented by the following equation:
CaCO₃(s) + 2HNO₃(aq) → Ca(NO₃)₂(aq) + CO₂(g) + H₂O(l)

If the concentration of nitric acid against time is plotted, the following graph will be obtained.
How do you calculate the reaction rate 8
The above graph is obtained based on the following facts:

Concentration of nitric acid decreases with time.
At the end of the reaction, all the nitric acid is completely reacted and its concentration becomes zero. This is due to the marble used in the reaction is in excess.

If the mass of marble against time is plotted, the following graph will be obtained.
How do you calculate the reaction rate 9
The above graph is obtained based on the following facts:

Mass of marble decreases with time.
At the end of the reaction, marble is in excess and m grams of marble remains unreacted.

If the concentration of calcium nitrate produced against time is plotted, the graph in Figure 1.8 is obtained.
How do you calculate the reaction rate 10
The above graph is obtained based on the following facts:

As more and more calcium nitrate is produced, the concentration of calcium nitrate increases with time.
When the reaction stops at time t, the concentration of calcium nitrate attains a maximum value, c mol dm^-3.

If the volume of carbon dioxide gas produced against time is plotted, the following graph is obtained.
How do you calculate the reaction rate 11
The above graph is obtained based on the following facts:

As more and more carbon dioxide gas is produced, volume of carbon dioxide gas increases with time.
When the reaction stops at time t, the total volume of carbon dioxide gas achieves a maximum value, V cm³.

An experiment is carried out using the apparatus set-up as shown in Figure.
How do you calculate the reaction rate 12
Chemical equation for the reaction is
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
If the mass of the conical flask and its contents against time is plotted, the graph in Figure is obtained.

The above graph is obtained based on the following facts:

As the reaction proceeds, more and more hydrogen gas is produced. The gas escapes to the surroundings.
Thus, the total mass of the conical flask and its contents decreases with time.
When the reaction stops at time t, no more hydrogen gas is produced. Hence, the total mass of the conical flask and its contents achieves a minimum value, w g.

How do you calculate the reaction rate experiment

Aim: To determine the average rate of reaction and the instantaneous rate of reaction.
Materials: Granulated zinc, 0.1 mol dm^-3 hydrochloric acid, water.
Apparatus: 150 cm³ conical flask, burette, stopper fitted with a delivery tube, retort stand and clamp, stopwatch, basin, electronic balance, 50 cm³ measuring cylinder.
Procedure:

25 cm³ of 0.1 mol dm^-3 hydrochloric acid is measured and poured into a conical flask.
A burette is filled with water until it is full. It is then inverted over water in a basin and clamped vertically using a retort stand.
The water level in the burette is adjusted and the initial burette reading is recorded.
The apparatus as shown in Figure is set up.
5 g of granulated zinc is weighed using an electronic balance.
The granulated zinc is added into the conical flask.
The conical flask is closed immediately with a stopper fitted with a delivery tube as shown in Figure and the stopwatch is started at the same time.
The conical flask is shaken steadily throughout the experiment.
The volume of gas collected in the burette is recorded at intervals of 30 seconds for a period of 6 minutes.
The results are tabulated in a table.

Results:

Time (s)	0	30	60	90	120	150	180	210	240	270	300	330	360
Burette reading (cm³)	48.90	41.40	37.15	34.40	32.40	30.65	29.15	27.90	27.15	26.40	25.65	25.15	24.90
Volume of gas liberated (cm³)	0	7.50	11.75	14.50	16.50	18.25	19.75	21.00	21.75	22.50	23.25	23.75	24.00

Interpreting data:

A graph of the volume of hydrogen gas liberated against time is plotted.
To calculate the average rate of reaction
To calculate the instantaneous rate of reaction

Discussion:

The instantaneous rate of reaction at 30 seconds (0.19 cm³ s^-1) is higher than the instantaneous rate of reaction at 90 seconds (0.08 cm³ s^-1).
The difference in rate is due to
(i) the concentration of hydrochloric acid at 90 seconds is lower than the concentration of hydrochloric acid at 30 seconds.
(ii) the total surface area of solid zinc at 90 seconds is smaller than the total surface area of solid zinc at 30 seconds.
From the graph plotted, it can be seen that the gradient of the curve decreases with time. Hence, the rate of reaction decreases with time.
As the reaction proceeds, the total surface area of zinc and the concentration of hydrochloric acid decrease with time. Hence, the rate of reaction also decreases with time. The rate of reaction will finally become zero, that is, the reaction stops when one or both the reactants are completely reacted.
The chemical equation for the reaction in this experiment is:
Zn(s) + 2HCl → ZnCl₂(aq) + H₂(g)
Another method that can be used to measure the rate of reaction between zinc and hydrochloric acid is by measuring the change in mass of the conical flask and its contents against time.

Conclusion:
As a reaction proceeds, the rate of reaction decreases with time until it becomes zero, that is, the reaction finally stops.

Rate of Reaction Calculation

Solving numerical problems
Examples about the calculation of the average rate of reaction and instantaneous rate of reaction are shown below.

1. 0.1 g of calcium carbonate is added to excess hydrochloric acid. The reaction stops after 15 seconds. 24.0 cm³ of carbon dioxide gas is collected. Calculate the average rate of reaction in
(a) g s^-1
(b) mol s^-1
(c) cm³ s^-1.
[Relative atomic mass: C, 12; O, 16; Ca, 40]
Solution:

2. In an experiment, one spatulaful of manganese(IV) oxide powder (as a catalyst) is added to 50 cm³ of sodium chlorate solution.

The oxygen gas liberated is collected in a burette by downward displacement of water. Its volume is recorded at intervals of 2

(s)	0	20	40	60	80	100	120	140	160	180	200	220	240	260	280
Volume of oxygen gas (cm³)	0.00	12.00	20.50	26.50	31.50	35.50	39.00	41.50	43.50	45.50	46.50	47.50	48.50	48.50	48.50

(a) Plot a graph of the volume of oxygen gas collected against time.
(b) Calculate the average rate of reaction
(i) in the first 2 minutes.
(ii) in the second minute.
(iii) for the overall reaction.
(c) Calculate the instantaneous rate of reaction
(i) at 20 seconds.
(ii) at 80 seconds.
Solution:
(a)
How do you calculate the reaction rate 21

0 seconds for a period of 280 seconds. The results are shown in Table.

Time

How does the temperature affect the rate of a chemical reaction?

December 1, 2020December 1, 2020 by Veerendra

How does the temperature affect the rate of a chemical reaction?

Effect of temperature on the rate of reaction:

When the temperature increases, the rate of reaction also increases.
(a) For example, two sets of experiments are carried out using the reacting conditions below:
Set I: 1 g of granulated zinc and 20 cm³ of 0.2 mol dm^–³ hydrochloric acid at 60°C
Set II: 1 g of granulated zinc and 20 cm³ of 0.2 mol dm^–³ hydrochloric acid at 30°C
(b) The rate of reaction of set I is higher than that of set II.
(c) This is because the temperature (60°C) of the reacting mixture in set I is higher than the temperature (30°C) of the reacting mixutre in set II.
When investigating experimentally the effect of temperature on the rate of reaction,
- the experiment is repeated a few times, each time using a different temperature of a reactant.
- all the other factors/conditions are kept constant in all the experiments.
The following shows an example of the effect of temperature on the rate of reaction. Table shows the method to derive the shapes of curves plotted for two sets of experiments.

How does the temperature affect the rate of a chemical reaction 1

People also ask

Effect of temperature on rate of reaction experiment

Aim: To investigate the effect of temperature on the rate of reaction.
Problem statement: How does temperature affect the rate of reaction?
Hypothesis: An increase in temperature will increase the rate of reaction.
Variables:
(a) Manipulated variable : Temperature ot sodium thiosulphate solution
(b) Responding variable : Rate of reaction
(c) Controlled variables : Volume and concentration of sodium thiosulphate solution, volume and concentration of sulphuric acid, size of conical flask
Operational definition:
Rate of reaction is inversely proportional to the time taken for the mark ‘X’ to disappear from sight.
How does the temperature affect the rate of a chemical reaction 2
Materials: 0.2 mol dm^–³ sodium thiosulphate solution, 1 mol dm^–³ sulphuric acid, white paper with a mark ‘X’ at the centre.
Apparatus: 150 cm³ conical flasks, 50 cm³ measuring cylinder, 10 cm^–³ measuring cylinder, digital stopwatch (electronically operated with an accuracy of 0.01 s), thermometer, Bunsen burner, tripod stand, wire gauze.
Procedure:

50 cm³ of 0.2 mol dm^–³ sodium thiosulphate solution is measured using a measuring cylinder and poured into a conical flask.
The temperature of this solution is measured using a thermometer.
The conical flask is placed on top of a piece of white paper with a mark ‘X’ at the centre.
5 cm³ of 1 mol dm^–³ sulphuric acid is measured using a 10 cm³ measuring cylinder.
The sulphuric acid is then poured quickly and carefully into the conical flask and a stopwatch is started immediately.
The mixture in the conical flask is swirled a few times. The conical flask is then placed back on the white paper.
The mark ‘X’ is viewed vertically from the top through the solution, as shown in Figure.
The stopwatch is stopped immediately once the mark ‘X’ disappears from sight.
The time f required for the mark ‘X’ to disappear from sight is recorded.
Steps 1 to 9 are repeated using 50 cm³ of 0.2 mol dm^–³ sodium thiosulphate solution at 35°C, 40°C, 45°C and 50°C respectively by heating the solution as shown in Figure before 5 cm³ of 1 mol dm^–³ sulphuric acid is added. All other conditions remain unchanged.
The results are recorded in a table.

Results:

Interpreting data:
1. Based on the results, two graphs are plotted.
(a) Graph I: Graph of the temperature against time
(b) Graph II: Graph of the temperature against 1/time
How does the temperature affect the rate of a chemical reaction 5
2. From graph I, it can be deduced that as the temperature increases, the time taken for the mark ‘X’ to disappear from sight becomes shorter.
3. From graph II, it can be deduced that the temperature increases linearly with 1/time.

Discussion:

(a) From the graphs plotted, the following inference can be deduced:
“Temperature increases linearly with 1/time”
(b) But, rate of reaction ∝ 1/time.
(c) Hence, rate of reaction increases linearly with temperature.
In other words, as the temperature increases, the rate of reaction also increases.
Usually, the rate of a reaction approximately doubles for every 10°C rise in temperature.
The concentration and volume of both sodium thiosulphate solution and sulphuric acid are kept constant in each set of the experiment. Any change in rate of reaction is due to the difference in temperature.

Conclusion:
Rate of reaction increases when the temperature of the reaction increases. Hence, the hypothesis can be accepted.

How does the surface area affect the rate of reaction?

December 1, 2020December 1, 2020 by Veerendra

How does the size of particles affect the rate of reaction?

Effect of surface area on the rate of reaction:

When the particle size of a fixed mass of a solid reactant becomes smaller, the total exposed surface area becomes larger, the rate of reaction increases.
- For example, two sets of experiments are carried out using the reacting conditions below:
  Set I: 1 g of zinc powder and 20 cm³ of 0.2 mol dm^–³ hydrochloric acid at room conditions.
  Set II: 1 g of granulated zinc and 20 cm³ of 0.2 mol dm^–³ hydrochloric acid at room conditions.
- The rate of reaction for set I is higher than that for set II.
- This is because 1 g of zinc powder used in set I has a larger total exposed surface area than 1 g of granulated zinc.
When investigating experimentally the effect of particle size/surface area on the rate of a reaction,
- the experiment is carried out twice
- the particle size/surface area of a solid reactant used in the two experiments are varied
- all the other factors/conditions are kept constant in both the experiments.
(a) The reaction between reactive metals and dilute acids to liberate hydrogen gas can also be used to study the effect of surface area on the rate of reaction.
Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)
Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)
(b) Rate of reaction of reactive metals such as magnesium, aluminium, zinc or iron with dilute acid is affected by the size of the metals.
(c) The smaller the size of a fixed mass of magnesium, aluminium, zinc or iron, the larger the total exposed surface area and the higher is the rate of reaction with dilute hydrochloric acid or dilute sulphuric acid.
An example of the effect of size of a solid reactant on the rate of reaction is shown in Table.

Experiment	Initial rate of reaction	Maximum volume of hydrogen gas
Set I: 1 g of granulated iron + 50 cm³of 0.2 mol dm^–³sulphuric acid Set II: 1 g of iron filings + 50 cm³ of 0.2 mol dm^-3sulphuric acid	Initial rate of reaction of set II is higher than that of set I because the total exposed surface area of 1 g of iron filings is larger than that of 1 g of granulated iron.	The quantities of iron and sulphuric acid used, in mole, in both sets I and II are the same. Thus, the maximum volume of hydrogen gas collected in both sets I and II are also the same.

Graph:

People also ask

How surface area affects the rate of reaction experiment

Aim: To investigate the effect of total exposed surface area of a solid reactant on the rate of reaction.
Problem statement: How does the total exposed surface area of a solid reactant affect the rate of reaction?
Hypothesis: When the total exposed surface area of marble chips increases, the rate of reaction increases.
Variables:
(a) Manipulated variable : Total exposed surface area of marble chips
(b) Responding variable : Rate of reaction
(c) Controlled variables : Mass of marble, volume and concentration of hydrochloric acid, temperature
Operational definition:

Smaller marble chips have a larger total exposed surface area than larger marble chips of the same mass.
For the graph of the volume of gas liberated against time, the curve with higher initial gradient indicates a higher initial rate of reaction.

Materials: 0.1 mol dm^–³ hydrochloric acid, large marble chips, small crushed marble chips, water.
Apparatus: 100 cm³ measuring cylinder, 150 cm³ conical flask, stopper fitted with a delivery tube, basin, burette, electronic balance, stopwatch.
Procedure:

A burette is filled with water until it is full. It is then inverted over water in a basin and clamped vertically using a retort stand.
The water level in the burette is adjusted and the initial burette reading is recorded.
40 cm³ of 0.1 mol dm^–³ hydrochloric acid is measured using a measuring cylinder and poured into a conical flask.
The apparatus as shown in Figure is set up.
2 g of large marble chips is weighed using an electronic balance and added to the acid in the conical flask. The conical flask is closed immediately with a stopper fitted with a delivery tube. At the same time, a stopwatch is started.
The carbon dioxide gas released is collected in the burette by downward displacement of water as shown in Figure.
The conical flask is shaken gently throughout the whole experiment.
The volume of gas collected in the burette is recorded at regular intervals of 30 seconds until no more gas is liberated.
Steps 1 to 8 are repeated using 2 g of small crushed marble chips to replace 2 g of large marble chips. All the other conditions remain unchanged.

Results:
Using large marble chips:
How does the surface area affect the rate of reaction 4
Using small crushed marble chips:

Interpreting data:
1. The graphs of volume of carbon dioxide gas liberated against time for both sets of the experiments are plotted on the same axes, as shown in Figure.
How does the surface area affect the rate of reaction 6

2. To calculate the instantaneous rate of reaction
How does the surface area affect the rate of reaction 7
(c) By comparison, the instantaneous rate of reaction at 1 minute of the experiment using small crushed marble chips is higher than that of the experiment using large marble chips.

3. To calculate the overall average rate of reaction
How does the surface area affect the rate of reaction 8
(c) By comparison, the overall average rate of reaction of the experiment using small crushed marble chips is higher than that of the experiment using large marble chips.

Discussion:

The reaction between marble chips and hydrochloric acid releases carbon dioxide gas. The chemical equation for the reaction is:
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + CO₂(g) + H₂O(l)
- Based on the graphs plotted, the curve for the experiment using small crushed marble chips is steeper than the curve for the experiment using large marble chips.
- In other words, the initial gradient of the curve for the experiment using small crushed marble chips is higher than the initial gradient of the curve for the experiment using large marble chips.
- Thus, the inital rate of reaction for the experiment using small crushed marble chips is higher than that for the experiment using large marble chips.
- Small crushed marble chips have a larger total exposed surface area than the large marble chips with the same mass.
- Hence, it can be concluded that:
  When the size of a fixed mass of solid marble becomes smaller, the total exposed surface area becomes larger, hence the rate of reaction increases.
- The above graph shows that the maximum volume of carbon dioxide gas collected in both experiments are the same, that is, 43.0 cm³.
- This is because the quantities of hydrochloric acid and marble used, in mole, are the same in both experiments.
- Theoretical maximum volume of carbon dioxide gas that should be collected can be calculated as follows:
  Number of moles of hydrochloric acid used
- The maximum volume of carbon dioxide gas collected in the experiment is less than the theoretical volume because a small volume of the carbon dioxide has dissolved in the water when it is collected in the burette.
- A method to overcome this difference is by saturating the water with carbon dioxide gas before collecting the gas in the burette.

Conclusion:
When the total exposed surface area of a solid reactant increases, the rate of reaction also increases. Hence, the hypothesis can be accepted.