Chapter 12 Laboratory: Chemical Kinetics 219SBSTITUTIU oNS ANd modIfICATIoNS- You may substitute small (~1 cm) pieces of chalk
(calcium carbonate) for the calcium carbonate antacid
tablets. - In making up the dilute hydrochloric acid solutions,
you may substitute muriatic acid from the hardware
store, which is typically 31.45% (10.3 M), for reagent
grade hydrochloric acid, which is typically 37% (12 M).
Adjust quantities accordingly.
LABORATORY 12.3:
dETERmINE THE EffECT of CoNCENTRATIoN oN REACTIoN RATE
Reactions proceed faster at higher
concentrations because more reactant
molecules are available and therefore
collisions between reactant molecules are
more likely. In the two preceding labs, we used
Alka-Seltzer tablets and water to demonstrate
the effects of temperature and surface area
on reaction rates. Obviously, we’ll have to use
some other method to demonstrate the effect
of concentration on reaction rates, because
the amounts of the citric acid and sodium
bicarbonate reactants in a fizzy tablet are
fixed and cannot be changed.
RIREEqU d EqUIpmENT ANd SUppLIES£ goggles, gloves, and protective clothing£ balance and weighing papers£ graduated cylinder, 100 mL£ thermometer£ timer£ foam cup (3)£ marking pen£ calcium carbonate antacid tablets (3)£ hydrochloric acid, 4 m (100 mL)£ hydrochloric acid, 2 m (100 mL)£ hydrochloric acid, 1 m (100 mL)£ waterIn this lab, we’ll use another OTC medicine with varying
concentrations of hydrochloric acid to demonstrate the effect
of concentration on reaction rates. Some (but not all) antacid
tablets contain primarily calcium carbonate, along with flavoring,
binders, and other inactive ingredients. These tablets neutralize
excess stomach acid, which is actually dilute hydrochloric acid,
according to the following equation:
CaCo 3 (s) + 2HCl(aq) → CaCl 2 (aq) + Co 2 (g) + H 2 o(l)
We’ll use exactly this reaction to observe and quantify the effect
of concentration of reaction rates.
CUTIOA nS
Hydrochloric acid is corrosive and emits strong fumes. Wear
splash goggles, gloves, and protective clothing at all times.z
POCEDURER
1.ou have not already done so, put on your splash If y
goggles, gloves, and protective clothing.
- Label three foam cups 4 M, 2 M, and 1 M.
- In the first foam cup, make up 100 mL of 4 M hydrochloric
acid by adding 33.3 mL of 12 M HCl to 66.7 mL of water.
Again, make sure that the combined mass of the foam
cup, antacid tablet, and 100 mL of hydrochloric acid is
less than the maximum capacity of your balance. If not,
reduce the quantity of hydrochloric acid accordingly.) - In the second foam cup, make up 100 mL of 2 M
hydrochloric acid by adding 16.7 mL of 12 M HCl to
83.3 mL of water.