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.
Small (2-6)97 ml132 ml205 ml239 ml315 mlMedium (6-9)70 ml118 ml180 ml216 ml273 mlLarge (9-12)45 ml100 ml152 ml200 ml249 mlI decided to use large marble chips (9-12mm) as the small and medium chips reacted much faster producing much more gas thanks to their large surface area. The amounts of gas produced by the small and medium samples of marble chips was so great it required us to change measuring cylinders half way through the experiment. With large marble chips less gas is produced saving me the inaccuracy of changing measuring cylinders.
To conduct my actual experiment I will follow the following plan:-稦irst I made five different concentrations of hydrochloric acid. (2 moles/dm�, 1.6 moles/dm�, 1.2 moles/dm�, 0.8 moles/dm�, 0.4 moles/dm�.) They all were 50ml in volume.
稩 then weighted out 5 lots of 5.5g抯 of marble chips to 2d.p of accuracy. We then put them together with their adjourning sample in a air tight conical flask.
稩 immediately started my stop clock. My conical flask had a air tight hose running into a upside measuring cylinder full of water. As my experiment produced gas it ejected the water from the measuring cylinder giving me a gas reading. I took readings of the gas levels every minute for five minutes.
稩 repeated every concentration twice so I could calculate an average to increase accuracy and reliability.
I washed my conical flask out after every reaction finished, so the next reaction would not become contaminated by the previous substances.
This is the equipment I used and what it resembled when set up.
I also had clamp stands which held my conical flask and measuring cylinder in place.
To ensure safety throughout the experiment I wore safety goggles at all times. I will record each sample of marble chips weight when I perform my investigation. This might help me understand any anomalies I might encounter.
I predict that as I decrease molarity of my hydrochloric acid , my reaction will slow down resulting in less gas production. I also predict that if I double my acid concentration I will double the volume of gas produced from the corresponding minute from the previous concentration. I predict a rise in gas production alongside acid molarity increase because, the increase in acid molarity means there are...