Mr

Carbonates react with strong acids to give off carbon dioxide and water. Marble is calcium carbonate and thus behaves in the same way:

CaCO3 (s) + 2HCL (aq)  CaCL2 (aq) + H2O (l) +CO2 (g)

In this experiment, I am going to see if temperature affects the reaction rate between marble chips and hydrochloric acid by timing the release of carbon dioxide in the reaction.

I predict the higher the temperature, the faster the reaction rate. This is due to the kinetic theory. The more heat that is given to matter, the faster the particles move. This happens in the acid, so the faster the particles move, the faster the reaction rate due to more collisions between the marble chips and the acid.

To help me plan out an adequate experiment and to find a suitable reading range, I will do a small preliminary experiment. Here is what apparatus I will use:

(Draw Apparatus)

I will wear goggles due to the fact that I am handling acid. I am going to take 3 readings in this preliminary experiment to see if the experiment works and takes place inside a suitable time range. I used 5g marble chips and 50ml hydrochloric acid. I am going to take readings from the top of my approximate range and from the bottom. I will also take one in the middle. This will help me to see if my range is appropriate.

I heated up the acid in the conical flask first until it reached the desired temperature. Next I placed the marble chips in and the delivery tube. I then timed how long it took to collect 50cm cubed of air in the burette. Here are the results of the preliminary.

(write or make up results)

I was careful to make this a fair teat by keeping all variables (apart from temperature) constant. To keep the marble chip surface area the same, I used only large chips. I used the same acid every time to keep the acid concentration the same and always used the same amount of materials.

The preliminary showed that the experiment worked. The timeframe is not too long or short either and can be easily measured. The range is OK, but I must be careful to not go over 70Ñ"C as I spotted some hydrochloric acid vapours, anything over 70Ñ"C would be dangerous. I will make one adjustment to the preliminary by heating the acid separately, and then, when it has reached the desired temperature to pour it in through the thistle funnel into the marble chips. This allows me to start timing the experiment straight away and there should be more accuracy involved. The results from the preliminary fit in with my prediction although more readings are needed.

Obtaining Evidence

(draw diagram)

I set up the apparatus as shown in the diagram above. I took precautions to wear goggles because I was handling acid. I followed the steps I had laid out in the plan with the changes that I made after the preliminary. I was careful not to start timing as I poured in the acid. This is because the gas released wouldnÒ't be produced by reaction but the displacement of air by the acid.

To keep this experiment a fair one, I had to keep all variables apart from temperature the same. The variables were:

Amounts of materials used

Surface area of marble chips

Concentration of acid

I made sure I used the same mass of marble chips each time and the same volume