Chemistry - Rates of Reaction Investigation

Chemistry Coursework - Rates of Reaction Investigation

Introduction

In this investigation I am going to be investigating the reaction between marble chips and hydrochloric acid, and to see what differences in the rate of this reaction arise when different concentrations of acid are used. Below is the word equation for this reaction:

Calcium Carbonate + Hydrochloric Acid = Calcium Chloride + Carbon Dioxide + Water

Below is the fully balanced chemical equation for this reaction.

CaCo3 + HCl  CaCl2 + CO2 + H2O

Aim

The aim of this investigation is to find out whether the concentration of the acid affects the rate of reaction between the acid and marble chips.

Prediction

I predict that, as the concentration of acid in the test tube increases, so too will the rate of reaction. I think this because concentration relates to the amount of molecules in the acid, and if there is a higher concentration of acid there is a larger amount of hydrogen chloride molecules in the acid and therefore they are more likely to collide and react with the calcium carbonate ions present in the marble chips. I would expect the following graph to emerge from the results:

Plan

Before I begin my real experiment, I had to do some preliminary testing. Firstly I set up the apparatus exactly as it would be in the proper experiments. Secondly I experimented with the mass of marble chips and amount of acid used in the experiments. I decided to use acid concentrations ranging from 0.5Mol to 2Mol, and increasing in 0.5Mol increments. The marble chips were measured out into masses of 1.5g. In this preliminary test I measured the amount of gas released in the reaction every thirty seconds for three minutes. Below is the table of results for this preliminary test:

Time 0.5mol 1mol 1.5mol 2mol

30secs 6cm3 10cm3 20cm3 31cm3

1min 12cm3 24cm3 38cm3 57cm3

1min30 18cm3 36cm3 55cm3 78cm3

2min 23cm3 46cm3 69cm3 95cm3

2min30 27cm3 55cm3 83cm3 110cm3

3min 30cm3 61cm3 93cm3 120cm3

The table shows me that the method of timing these results is sufficient. However, I have realised that I will need to add some concentrations because of the lack of points available for the final graphs. Since the maximum concentration of acid allowed is 2mol, I am going to reduce the incremental value to 0.25mol; therefore giving me the concentrations 0.5mol, 0.75mol, 1mol, 1.25mol, 1.75mol, and 2mol. I am confident that these concentrations will give me sufficient results for my final graphs, so I feel there is no need for further preliminary testing.

Safety Precautions

There are only a few safety precautions relevant to this experiment, giving its relative docility. These are:

* Keep long hair and ties tied back/under a jumper;

* Push bags under desks & keep the floor clear;

* Do not contaminate/mix/spill the acids;

* Make sure equipment is securely in place.

Arrangement of Apparatus

Below is the illustration for the way my apparatus is going to be set up for the experiment.

Measurements

I am going to measure the amount of gas released over 3 minutes, taking measurements every thirty seconds. I will read the values off of the gas measuring cylinder, repeating the experiment three times to give me three results for each concentration. Then, after these have been recorded, I will take an average of these results to give me one averaged result.

Fair Testing

In the interests of fair testing, I am going to do a few things. These include:

* Keeping the mass of marble chips stable at 1.5g for every stage of the experiment;

* Try not to let the room temperature vary too much to make an impact on my results;

* Use the same amount of hydrochloric acid (10ml) for every reaction.

The Final Experiment

I am now going to conduct my real experiment, after obtaining sufficient information from the preliminary tests to have a more precise idea of the experiment. Here is the table of results for my experiment:

Time 0.5mol 0.75mol 1mol 1.25mol 1.5mol 1.75mol 2mol

30secs 6 cm3 8 cm3 8 cm3 18 cm3 20 cm3 25 cm3 28 cm3

30secs(2) 7 cm3 9 cm3 10 cm3 16 cm3 21 cm3 23 cm3 31 cm3

30secs(3) 6 cm3 8 cm3 12 cm3 17 cm3 19 cm3 24 cm3 33 cm3

1min 11 cm3 20 cm3 22 cm3 30 cm3 35 cm3 50 cm3 54 cm3

1min(2) 12 cm3 19 cm3 24 cm3 31 cm3 38 cm3 51 cm3 57 cm3

1min(3) 10 cm3 19 cm3 26 cm3 30 cm3 36 cm3 51 cm3 60 cm3

1min30 17 cm3 31 cm3 35 cm3 50 cm3 55 cm3 73 cm3 76 cm3

1min30(2) 18 cm3 28 cm3 36 cm3 49 cm3 55 cm3 72 cm3 78 cm3

1min30(3) 20 cm3 30 cm3 37 cm3 51 cm3 57 cm3 73 cm3 79 cm3

2min 22 cm3 40 cm3 46 cm3 61 cm3 69 cm3 91 cm3 93 cm3

2min(2) 23 cm3 37 cm3 46 cm3 63 cm3 70 cm3 93 cm3 95 cm3