The reaction proceeds quite rapidly during the initiate mixture of Hydrochloric acid and Calcium Carbonate chips. Between 1-3 min the reaction is proceeding vigorously, however later on between 4-6 min the reaction tampers off and the consumption in HCl lowers per min intervals.
The experimental design appears to be very vague on the actually mixing of the HCL with CaCO3. It doesn’t specify at what quantity the CaCO3 chips that are supposed to be mixed with the 1.9mol/L HCL solution. Therefore you can only assume from the molar ratio of 2:1 and use .95mol. It also doesn’t explain if the mixture can be stirred or shaken which would also affect the rate of reaction.
Finally, because the materials list 1.90mol/L of hydrochloric acid is to be used and you begin with a concentration of 1.90mol/L, you must assume you are using a 1L solution. This is quite an excessive amount of solution for a small scale experiment and could potentially give you different pH readings if the measuring device isn’t kept in a constant spot.
In my prediction, I assumed there would be a constant change in the concentration of HCl over the 6 minutes. My graph showed a consistent decline of -0.30mol/Lmin, which was incorrect as shown by the experiment. I also indicated that after 6min there would be a remaining concentration of .1mol/L of HCl which was also incorrect, because the experimental HCl had .72mol/L concentration after 6mins; a much slower rate of reaction than I had anticipated.
Rate of Consumption of HCl at 1 min: -0.41mol/Lmin
∆CaCO3 /∆t = (1mol CaCO3 / 2mol HCl) -0.41mol/Lmin= -2.05 x10 -1 mol/Lmin
∆CO2 /∆t = (1mol CO2 / 2mol HCl) 0.40mol/Lmin= 2.05 x10 -1 mol/Lmin
Conductivity could be measured using an ammeter or for extremely small measurements, a galvanometer can be used. High rates of reaction would cause an increase ionic electron exchange and thus electric current. So measuring the conductance of solutions can tell you whether the solutes in the solution are dissociated into ions and whether chemical reactions in solution are producing or consuming ions.
This conductivity, once measured, can be plotted graphically as a function of time. In addition, gas vapours can be collected during the experiment and the experimenter can measure its volume and/or pressure as the reaction proceeds. Increasing pressure at the same volume means more atoms are being liberated and the rate of reaction.