Illustrated Guide to Home Chemistry Experiments

Chapter 11 Laboratory: Acid-Base Chemistry 199

RQEWEvI UESTIOnS

q 1 : What general conclusions can you draw from the pH values that you observed for the four solutions?

q: 2 If you mixed equal amounts of a 0.1 M ammonium chloride solution and a 0.1 M sodium acetate solution, would you expect the
pH of the resulting solution to be strongly acidic, weakly acidic, about neutral, weakly basic, or strongly basic? Why?

CUTIOA nS

Although none of the salts used in this lab are

particularly hazardous, it’s good practice to wear

splash goggles, gloves, and protective clothing at all

times. If you make up the salt solutions from acid and

base solutions as described in the Substitutions and

Modifications section, use the normal precautions for

working with acids and bases.

z

POCEDURER

1.ou have not already done so, put on your splash If y

goggles, gloves, and protective clothing.

2. Using what you know about strong and weak acids
   and bases, predict the approximate pH values for the
   solutions of the four chemicals and enter your predicted
   values in Table 11-2 by circling one of the pH numbers. If
   you are uncertain, circle a range of numbers.


3. Pour about 100 mL of 0.1 M ammonium acetate into the
   beaker.


4. Read and follow the directions for your pH meter with
   respect to calibrating it, rinsing the electrode between
   measurements and so on. Use the pH meter to measure
   the pH of the ammonium acetate solution, and record the
   observed value on the appropriate line of Table 11-2.


5. Repeat steps 3 and 4 for the solutions of ammonium
   chloride, sodium acetate, and sodium chloride.

dISpoSAL: All of the solutions used in this laboratory

can be flushed down the drain with plenty of water.

TABLE 11-2: Determine the pH of aqueous salt solutions—observed and calculated data

Solute Predicted pH Observed pH

A. Ammonium acetate 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ____.___ pH

B. Ammonium chloride 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ____.___ pH

C. Sodium acetate 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ____.___ pH

D. Sodium chloride 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ____.___ pH