Experiment to investigate the effect of the concentration on the rate of reaction

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Experiment to investigate the effect of

the concentration on the rate of reaction

Introduction: -

Rate of reaction is the measure of the length of time taken for a reaction to occur. Factors that affect the rate of reaction are (This is the general view, check hypothesis):-

  1. Temperature of the Solution
  2. Surface Area of the Solid
  3. Concentration of the Solution

Rate of reaction can be measured using several techniques. These involve measuring the rate of which the product is made or the rate at which a reaction is used up.

The balanced chemical equation and word equation reaction between Hydrochloric Acid and Calcium Carbonate is shown below:-

It can be seen from the equation that this reaction produces CO2 gas. Therefore, it is possible to measure the rate of reaction by measuring the volume of the gas produced within a certain length of time.

                                                 

Aim: -

To investigate the effect of changing the concentration of the Hydrochloric Acid on the rate of reaction between Hydrochloric Acid and Calcium Carbonate in the form of marble chips.

Hypothesis: -

What was kept constant: -   1.   Temperature of the Acid

  1. Concentration of Hydrochloric Acid
  2. The total weight of the Marble Chips
  3. Volume of the Hydrochloric Acid

Preliminary Experiment: -

This involved determine the size of the marble chips (calcium carbonate) to use in the experiment.

Equipment used to determine this: -

Diagram 1: -

Method: -

  1. Wear goggles for safety

  1. Temperature kept constant by placing Hydrochloric Acid in a water bath (this was constant at temperature 25ºC)

Concentration of Hydrochloric Acid was known. This was kept at 80 ml of Hydrochloric Acid.

Mass of chips weighed on digital balance and the only variable changed was the size of the chips.

  1. Volume of Carbon Dioxide gas produced at regular time intervals (every 5 seconds) was measured and noted.

  1. This was done only once for each size of chip.

Table on next page!!!

Results for the preliminary experiment: -

Volume of CO2 (g) produced (cm3) from the reaction between 2M Hydrochloric Acid and using different sized marble chips.

Outcome: -

From the preliminary investigation, small marble chips were chosen because the time taken for complete reaction was shorter i.e. faster rate of reaction (because of a larger surface area) therefore making the experiment easier to carry out.

Prediction: -

Prediction 1  It is predicted that increasing the concentration of the Hydrochloric Acid will increase the rate of reaction (i.e. it will produce a larger volume of CO2 within a certain length of time.)

Prediction 2  It is predicted that when the concentration of the Hydrochloric Acid is doubled then the rate of reaction will double.

These predictions are based on scientific knowledge i.e. the COLLISION THEORY

There are three basic assumptions that are made:-

  1. Molecules must collide and make contact before the any reaction can take place.
  2. Only molecules with a certain amount of kinetic energy react when the molecules collide.
  3. Molecules must collide in the correct relative position or direction if they are to react.
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This is explained in detail below !

Quantitative Prediction: -

The 2 Molar acid has twice the number of acid particles than the 1 Molar. This is cause would cause the particles of the 2M acid to have twice as much successive collisions as the 1M concentration of acid. This would therefore result to the rate of reaction doubling. (In this experiment, it is essential to keep the volume of the acid the same).

For example, 50 cm3 of 2M Hydrochloric Acid would contain the same number of acid particles as 100 cm3 of 1M Hydrochloric Acid despite the fact ...

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