The concentration of the reagent solution3. Experiment temperature4. Amount of time available for reaction5. Quantity of solid reagent6. Amount of Reagent Solution Particle Size The reaction between calcium carbonate and dilute hydrochloric acid is used to prepare CO2. By varying the size of the calcium carbonate you can make the reaction produce more or less carbon dioxide in the available time frame. I could try using lumps or powder and see which reaction would produce the most gas. This should be kept the same to ensure that the surface area of ​​the solid reactant remains the same as a larger surface area produces more gas than a smaller one. I decided to use marble chips as tests reveal that the powder allows for a lot of gas to be produced to achieve an accurate recording. Concentration Concentration is a very important factor in reaction speed. The concentration of a solution can greatly affect a reaction, because there will be more reagent particles to react with, which will increase the time taken for the reaction. If the concentration of an acid increases, the rate of the reaction will increase because the collision rate would be higher and the amount of CO2 would be released more quickly. That's why concentration