Rate of Reaction Practical Report

Rate of Reaction Practical Report

Aim:

To determine how the concentration of acid affect the rate of reaction

Hypothesis:

The hypothesis is that as the concentration of the hydrochloric acid increases the rate of reaction will increase.

Variables

Independent Variable: Concentration of Acid (M)

The variables used were (0.5m, 0.75m, 1m, 1.5m, and 2m)

Dependent Variable: Time taken for reaction to stop (Minutes)

Controlled Variable How to Keep it Constant? Why it needs to be kept constant?

Amount of Hydrochloric Acid used each time. Measure out 5ml of Hydrochloric Acid for each trial It needs to be kept constant to ensure a fair test. The amount of hydrochloric acid affects the rate of reaction because it can speed up or slow down the reaction, since the rate of the reaction is being measured the amount of hydrochloric acid has to be controlled.

Temperature (room temperature) Conduct the experiment in the same room temperature It needs to be kept constant because if one trial is done in a hot room temperature the temperature can acts as a catalyst and speed up the reaction, same as if one experiment is done in a cooler room temperature than the other the temperature can act as an inhibitor and slow down the reaction.

Size of Magnesium ribbon Measure 1.5cm of Magnesium ribbon for each trial It needs to be kept constant because the size surface area of the Magnesium ribbon affects the rate of reaction; bigger strip of Magnesium take a longer time for the reaction to stop compared to a smaller strip of Magnesium.

Equipment

1 x Test tube rack

1 x Beaker

1 x Pipette

1 x Measuring Cylinder

Method

1. Collect all the equipment needed including safety glasses and gloves

2. Measure and Pour 5ml of 0.5M Hydrochloric acid into a test tube

3. Measure and place the 1.5cm Magnesium ribbon into the test tube containing the hydrochloric acid and start the stopwatch

4. Observe the reaction and time until the bubbles stop forming

5. Repeat steps 1-3 for two more trials using the same amount of Hydrochloric acid and size of Magnesium ribbon

6. Repeat steps 2-5 using the same amount of higher hydrochloric acid (0.5M, 0.75M 1M, 1.5M, 2M) under the same room temperature

Risk or Hazard Why it is a risk or hazard Steps taken to minimise risk or hazard

Concentrated Acid Can cause eye damage, if exploded, and can burn skin. Wearing safety glasses during the experiment. Wearing gloves to avoid contact with bare skin.

Inhalation of Acid Can cause respiratory problems Keeping a decent distance between the Acid and trying to keep nose away from the acid.

Magnesium Ribbon It is a flammable solid Not exposing it to direct heat

Hydrogen gas It is explosive Using less concentrated acid to conduct the experiment.

Reaction

Magnesium Metal + Hydrochloric Acid

Mg + 2 HCl MgCl2 + H2

Results

Table 1: Showing how the reaction time changes with concentration

Concentration of Acids (M) Trial 1 (Min) Trial 2 (Min) Trial 3 (Min) Average (Min) 1/ Average Reaction Time(Min-1)

2 0.85 1.40 0.95 1.06 0.94

1.5 2.00 2.41 3.14 2.52 0.40

1 3.39 3.18 3.58 3.47 0.29

0.75 14.50 12.14 12.45 13.12 0.08

0.5 23.39 35.19 27.49 28.69 0.03

Discussion

The trends that can be observed from the data in Table 1 are that as the concentration of acid increases the rate of reaction also increase. This is due to the collision of particles. For a chemical reaction to occur, the reactant particles taking part in the reaction has to collide with each other. In this experiment the Magnesium ribbon which is in solid state collides with the Hydrochloric acid in liquid state. The Collison theory states that the rate of reaction depends on the rate of successful collisions between reactant particles. The more successful collisions there are, the faster the rate of reaction.1 The highest concentrated acid used was 2M and the average time for the reaction to occur was 1.06 minutes. The lowest concentrated acid used was 0.5M which took an average of 28.69 minutes to fully react. The more concentrated an acid is the more energy it will have. The 2M acid is highly concentrated making it have more energy enabling it to collide with the magnesium ribbon faster, hence having a higher rate of reaction. The concentration of the 0.5M acid is low, making it have less energy to collide with the Magnesium ribbon, hence having a slower rate of reaction. Since the rate of reaction is proportional 1/Average Reaction time as shown in graph 1, as the concentration of the reactant increases the rate of reaction of the products also increase.

Errors and Improvements

One error encountered in this experiment was that the magnesium ribbon was not polished with sandpaper before conducting this experiment. This is an error because Magnesium is a reactive metal, if it is exposed to oxygen for a long period of time it will start reacting with oxygen and form metal oxides. This will create a white layer on the outside of the ribbon. If the Magnesium is polished, the extra layer created through reacting with oxygen will be removed. This error affects the rate of reaction because the white layer on the outside of the not polished Magnesium will delay the reaction and affect the rate