Experiment to see how the quantity of marble chips affects the rate of reaction with hydrochloric acid.

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GCSE Chemistry - Experiment to see how the quantity of marble chips affects the rate of reaction with hydrochloric acid

Acids undergo three main reactions:

Acid + Alkali → Salt and water

Acid + reactive metal → Salt and hydrogen

Acid + carbonate → Salt, water and carbon dioxide

I am investigating how the rate of one of these reactions is influenced by changing an external factor. External factors are things you can change in an experiment e.g. temperature, concentration, volumes, amounts and surface area.

It is very important that only one external factor is altered, otherwise it is not a fair test. A fair test is when you keep all but one of the properties the same amount in each test, so you know how one particular factor affects it.

If the temperature was raised, the particles would move faster, therefore they collide faster and speed up the reaction rate. If it was lowered, the particles would move slower and take more time to collide, therefore slowing down the reaction rate. We call this the collision theory of kinetics.

If the concentration of the acid was altered in each experiment, and didn’t need to be, the results would all be inconsistent. If the concentration of the acid was lowered by diluting, there would be fewer particles to react with the other substance, meaning fewer reactions would take place. If the concentration of the acid wasn’t diluted enough, there would be more particles to react with the other substance, meaning more reactions would take place.

The volume, or amount of acid, would much be affected in the same way as the concentration. If the volume was increased, more reactions would take place. If it was decreased, fewer reactions could take place, as there would be fewer acid particles.

If it was an experiment reacting marble chips and acid, changing concentration of acid, we would keep the marble chips the same size. When the chips are broken up into small pieces, there is a large surface area touching the acid, meaning more reactions will take place. If large chunks were used, they would have a much smaller total surface area, meaning fewer reactions could initially take place.

Due to safety reasons, using acid and a reactive metal is not a sensible idea. One of the by products is hydrogen, which is explosive, therefore it is dangerous to carry out in a school science laboratory.

The reaction between acid and alkali is difficult to record. It has become apparent from previous experiments I have carried out, that there is a very sudden reaction between them. This means it is hard to work out how much its reaction is affected by changing an external factor. It is also not very clear what the universal indicator reads, as it is colour coded, you could be several PH points off what it actually is.

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Reacting an acid with a carbonate is safe, and it is easy to record the amount of carbon dioxide produced using an upside down measuring cylinder. I think this is the best reaction to study.

List of equipment:

  • Conical flask
  • Delivery tube with bung
  • 50ml of Hydrochloric acid
  • Clamp
  • Electric scales
  • Stop-clock

AND

  • Measuring cylinder
  • Large plastic tub filled with water

OR

  • Gas syringe

The acid which was available for the experiment was hydrochloric acid (HCl). The calcium carbonate we were provided with was in the form ...

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