In my investigation I will be investigating how changes in acid concentration (moles) effect the rate of reaction with marble chips. I will measure the rate of reaction by measuring the gas produced when the reaction occurs. My variable will be acid concentration , and I will keep every other aspect of my experiment the same. (Volume of acid, conical flask used, volume of water in collection basin.) This will ensure fair and accurate testing. Before I conducted my experiment I need to decide which size marble chips to use. We have 3 varieties: small (2-6mm) medium (6-9mm) and large (9-12mm). So I conducted a preliminary investigation to perfect my method, check for flaws and see which chips created the least amount of problems. However before I conducted preliminary or actual work I needed to calculate how many marble chips to use (grams) I used the following calculation:CaCO3 + 2HCL CaCl + CO2 +H20? 50mlThe calculation above is the symbol equation for the reaction that take place in my experiment.
I calculated the mass of CaCO3 in three steps:1. moles: moles = concentration X cm�00: 2 X 501000= 0.1 moles/dm� Ratio: 1CaCO3 : 2 HCL0.05 : 0.13. Mass : (mass = moles X Mr)0.05 X 100 =5gTherefore 50ml of Hydrochloric acid dissolves 5g抯 of calcium carbonate. However to maximize gas production we used an excess of marble chips. So the weight of chips weused for both my preliminary work and my real experiment was 5.5g抯.
So I used 50ml of 2 molar/dm� hydrochloric acid and 5.5g抯 of marble chips in my preliminary investigation. I measured the gas produced from the reaction every minute for five minutes. These were my results:Size (mm).1 min.2 min.3 min.4 min.5 min.