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
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.
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:
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:
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.
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.
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: