5 Steps to a 5 AP Chemistry 2019

Experimental Investigations ❮ 295

Calculations

The overall percent recovery for the sample would be the sum of the masses of all the recov-

ered components divided by the initial mass of the sample:

(sum of the grams of all recovered components/grams of sample) × 100%

The percentage of each component can be calculated by dividing the mass of a component

by the total mass of all recovered components:

(grams of component/sum of the grams of all recovered components) × 100%

Comments

Be very careful in making your measurements. The same general procedure can be applied

to a number of other systems.

Be especially careful when handling the acid solutions and organic solvents. Be sure to

vent the separatory funnel before opening it.

Experiment 10: Kinetics

Synopsis

In this experiment, some of the factors involved in the speed of a chemical reaction will be

explored. Commonly this experiment focuses on the decomposition of calcium carbonate—

limestone, CaCO 3 (s), and hydrochloric acid, HCl(aq). Pieces of calcium carbonate of dif-

ferent sizes (to test how the speed of reaction varies with surface area) and HCl solutions

of different concentrations will be available. The temperature of the reaction mixture can

be varied by using an ice bath or heating the mixture. In order to measure the speed of

the reaction, the carbon dioxide gas product can be collected in a syringe, or a gas pressure

probe can be used to monitor the production of the CO 2 (g) as a function of time. The mass

of sample consumed (or the decrease in the total mass of the reaction flask) versus time can

also be used as an indication of the speed of reaction.

Equipment

Balance

Hotplate

Syringes

Stopwatch

Assorted glassware

Magnetic stirrer and stir bar

Gas pressure probe and data collection device

Measurements

Measurements include the initial and final mass of the calcium carbonate sample, the

volume of gas evolved, and time measurements.

Calculations

Calculations commonly involve determining the mass of sample consumed (lost) as

a function of time. The results of the mass versus time measurements are commonly

plotted.