How Concentration Changes The Rate Of Reaction Between Sodium Thiosulphate And Hydrochloric Acid With Equation Graph And Experiment
In a reaction, many elements or compounds react together to form one or more new products based on the basic elements of the compounds involved in the chemical reaction. The reaction may occur between solids, liquids, and gases, and the rate of each reaction is different from another which depends on a number of factors. Some chemical compounds called catalysts or enzymes help in accelerating the rate of reaction. This rate of reaction is also dependent on the amount or concentration of substances involved in the reaction.
In this article, the effect of concentration on the rate of the reaction between sodium thiosulphate and hydrochloric acid has been discussed in the form of an experiment.
About the Rate of Reaction
In any chemical reaction, several reactants react to form one or more new products. These reactants can be gases, solids or even liquids. The rate of reaction depends on many determinants or factors. The presence of catalysts can also accelerate the speed of any reaction. One of the essential components that determine the rate of reaction is the concentration of the reactants taking part in the chemical reaction. In this article, we are going to study the effect of concentration on reaction rate by observing a chemical reaction. The results obtained from the reaction between Na2S2O3 and HCl helps you to understand the topic more clearly.
Aim
To understand the effect of concentration on the rate of reaction between sodium thiosulphate (Na2S2O3) and hydrochloric acid (HCl).
Theory
The rate of the reaction directly depends on the products of the molar concentration of reactants. In this experiment, we will study the reaction between Sodium thiosulphate (Na2S2O3) with hydrochloric acid (HCl).
Na2S2O3 (aq) + 2HCL (aq) → H2O (l) + SO2 (g)+ 2 NaCl (aq) + S (s)
We can also write the above reaction in ionic form as:
S2O3-2 (aq) + 2H+ (aq) → H2O (l) + S (s) + SO2 (g)
The solution obtained after the reaction is opaque and has a milky appearance due to the presence of sulphur. If we increase the temperature or concentration of the reactants, then the rate of precipitation of sulphur also increases. It happens because when concentration increases, molecular collisions also increase per unit time, which results in a fast rate of product formation.
The reaction is between the aqueous solutions of Na2S2O3 and HCl, the rate of which directly depends on the product of the molar concentration of each component of the reaction.
The chemical reaction formula between HCl and Na2S2O3 is as follows:
Na2S2O3 (aq) + 2HCL (aq) → H2O (l) + SO2 (g)+ 2 NaCl (aq) + S (s)
Here, we can see the products of the reaction are water, sulphur dioxide (SO2 ), sodium chloride (NaCl) and a sulphur atom. Where SO2 is formed in the gaseous state, NaCl is formed in the aqueous state and sulphur collects in the solid-state.
With the increase in the temperature of the system, the precipitation of sulphur increases. With the increase in concentration, a collision between molecules also increases which increases the chances of getting the products of the reaction, and an increase in temperature provides more kinetic energy to the reaction which in turn increases the rate of reaction, thereby, resulting in faster production of products.
Materials Required
The materials and apparatus required for conducting the reaction are as follows:
Five flasks of 100ml each
Two burettes of volume 50 ml each
Pipette
Burette stand
Stopwatch
Sodium thiosulphate
1M Hydrochloric acid
Five conical flasks (100 ml)
Two burettes
Burette Stand
Pipette
Stopwatch
Sodium Thiosulphate
1M Hydrochloric Acid Solution
Procedure
First of all, take five conical flasks and rinse them with water to clean any residue. Now, label them as 1, 2, 3, 4 and 5 respectively.
Draw the cross mark on any white tile.
Take a burette and add 10 ml of Na2S2O3 solution in flask 1 using it. Similarly, add 20 ml of Na2S2O3 solution in flask 2, 30 ml in flask 3, 40 ml in flask 4 and 50 ml solution in flask 5.
Now, add distilled water in every flask such that the combined volume of water and Na2S2O3 solution becomes 50 ml. It means we need to add 40ml, 30ml, 20 ml and 10 ml distilled water in flasks 1, 2, 3 and 4 respectively.
Take 10 ml of 1M HCl solution in a test tube using the burette. Add it in flask 1, which contains 40 ml water and 10 ml Na2S2O3. Shake it thoroughly and then start the stopwatch immediately.
Place the flask on the white tile having a cross mark. Observe the cross mark from the top and stop the stopwatch as the cross mark becomes invisible. Note the time taken for the whole process.
Repeat the same procedure with flask 2, 3, 4 and 5. Note the time when the cross mark becomes invisible in every container.
Wash the flasks and add 10ml of sodium thiosulphate in the first flask and add 10 ml more to each subsequent flask.
Add 40ml of distilled water in the first flask, 30ml in the second, 20ml in the third, 10ml in the fourth and none in the fifth flask.
10ml HCl is to be added to the first flask with the help of a burette and the stopwatch should be started immediately.
Take a white tile and put a cross mark on it distinctly. Put the first flask on the time and observe.
Observe till the solution is milky and the mark on the tile is visible and note the time right there.
Observations and Results
(Image will be uploaded soon)
The above image shows the graph between 1/t (on the y-axis) and the concentration of Na2S2O3 (on the x-axis). We will obtain a straight sloping line, as shown in the figure.
From the above graph, it is clear that 1/t is directly proportional to the concentration of Na2S2O3 solution taken during the experiment. We know that 1/t is the direct measure of the rate of reaction. Hence, the pace of chemical reaction in this case directly depends on the concentration of Na2S2O3. However, it doesn't mean that the speed of any chemical reaction doesn't depend on conc. of HCl. We will see a similar result if we keep the concentration of sodium thiosulphate constant and raise the concentration of hydrochloric acid. This experiment clearly shows the effect of concentration on Rate of Reaction.
The product formed from the reaction is milky in appearance due to the presence of sulphur. Increasing the temperature increases the rate of precipitation.
Noting the time and plotting a graph with 1/t on the y-axis and the concentration of Na2S2O3 on the x-axis where t is the time taken to form products at different concentrations. It was observed that the graph shows a straight sloping line which means that 1/t is directly proportional to the concentration of Na2S2O3 which means increasing the concentration increased the rate of reaction as well.
If the concentration of sodium thiosulphate was kept constant and the concentration of hydrochloric acid was increased, the same trend would be observed.
FAQs on Effect Of Concentration On The Rate Of Reaction Between Sodium Thiosulphate And Hydrochloric Acid Explained
1. What is the reaction between sodium thiosulphate and hydrochloric acid?
The reaction between sodium thiosulphate and hydrochloric acid produces sodium chloride, sulphur dioxide, sulphur, and water. The balanced chemical equation is:
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l)
- The reaction forms a yellow precipitate of sulphur (S).
- Sulphur dioxide (SO2) gas is released.
- This reaction is commonly used to study the effect of concentration on rate of reaction.
2. How does concentration affect the rate of reaction between sodium thiosulphate and hydrochloric acid?
Increasing the concentration of sodium thiosulphate increases the rate of reaction because more particles collide per second. According to collision theory:
- Higher concentration means more reacting particles in a given volume.
- Frequency of effective collisions increases.
- The time taken for the solution to turn cloudy decreases.
3. Why does the solution turn cloudy in the sodium thiosulphate and hydrochloric acid experiment?
The solution turns cloudy because solid sulphur (S) is produced during the reaction. In the reaction:
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l)
- Sulphur is insoluble in water.
- It forms a fine yellow precipitate.
- This precipitate blocks light, making the solution appear cloudy.
4. How do you measure the rate of reaction in the sodium thiosulphate and hydrochloric acid experiment?
The rate of reaction is measured by timing how long it takes for a cross beneath the flask to disappear due to sulphur formation. The method involves:
- Placing a conical flask over a marked cross.
- Adding hydrochloric acid to sodium thiosulphate solution.
- Starting a stopwatch immediately.
- Stopping timing when the cross is no longer visible.
5. What is the role of hydrochloric acid in the sodium thiosulphate reaction?
Hydrochloric acid provides H+ ions that react with thiosulphate ions to produce sulphur, sulphur dioxide, and water. In the reaction:
- HCl(aq) dissociates into H+(aq) and Cl−(aq).
- The H+ ions react with S2O32− ions.
- Chloride ions form aqueous NaCl.
6. What is the balanced equation for sodium thiosulphate and hydrochloric acid?
The balanced chemical equation is Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + SO2(g) + S(s) + H2O(l). This equation shows:
- Two moles of HCl react with one mole of sodium thiosulphate.
- Products include sodium chloride, sulphur dioxide, sulphur, and water.
- All atoms are balanced on both sides of the equation.
7. Why is the rate calculated as 1 divided by time in this experiment?
The rate is calculated as 1/time because the same fixed amount of sulphur is produced each time the cross disappears. Since:
- The endpoint is when visibility is lost.
- A constant amount of product is formed at that point.
- Shorter time means faster reaction.
8. What happens to the rate of reaction if the sodium thiosulphate solution is diluted?
Diluting sodium thiosulphate decreases the rate of reaction because fewer thiosulphate ions are present per unit volume. As a result:
- Collision frequency decreases.
- Fewer successful collisions occur per second.
- The time taken for the cross to disappear increases.
9. Is the reaction between sodium thiosulphate and hydrochloric acid exothermic or endothermic?
The reaction between sodium thiosulphate and hydrochloric acid is slightly exothermic, meaning it releases a small amount of heat. During the reaction:
- Energy is released when new bonds form in products.
- The temperature may rise slightly.
- The temperature change is usually small in school experiments.
10. What safety precautions should be taken in the sodium thiosulphate and hydrochloric acid experiment?
Safety precautions are necessary because hydrochloric acid is corrosive and sulphur dioxide gas is harmful. Important precautions include:
- Wear safety goggles and a lab coat.
- Carry out the experiment in a well-ventilated area.
- Avoid inhaling SO2 gas.
- Rinse spills immediately with plenty of water.
