5 Steps to a 5 AP Chemistry 2019

Experimental Investigations ❮ 289

Equipment

Various salt solutions of known concentration

Analytical balance

Drying oven

Suction filtration apparatus

Büchner funnel

Filter paper

Aspirator

Ring stands

Assorted glassware, including volumetric glassware

Measurements

The student will make several measurements in gravimetric analysis, especially mass and

volume determinations.

Calculations

If a water hardness analysis is being done, the grams of calcium carbonate per milliliter of

water sample are initially calculated. This value is then converted to milligrams of calcium

carbonate per liter of water sample (hardness) using appropriate conversions.

Comments

All measurements must be done accurately, especially the mass and volume measurements.

Experiment 4: Titration

Synopsis

In the titration procedure, the concentration of an acid is determined by adding small

quantities at a time of a base of known concentration until the point at which the moles of

base equal the moles of acid present (the equivalence point). It is possible to do a titration

by adding small amounts of a solution of a known concentration of acid to determine the

concentration of a base solution. Many times this neutralization point cannot be deter-

mined unaided, so an indicator or a pH meter is used. The point at which a color change

happens with the indicator or an abrupt change in pH occurs with the pH meter is called

the endpoint of the titration. Knowing the volume of the unknown acid, the concentra-

tion of the base, and the number of milliliters it took to reach the endpoint allows you to

calculate the concentration of the unknown acid. The concentration of an unknown base

can be determined by titration with an acid of known concentration (Figure 19.2).

Equipment

Burets

Erlenmeyer flasks

Pipets

Acid-base indicators

pH meter

Base or acid solution of known concentration

Assorted glassware

Measurements

You will be placing a required volume of the unknown acid (or base) solution into the

Erlenmeyer flask with a pipet. The buret will be filled with the base (or acid) solution. Be