Name ________________________________ Chem 178L Sp 01 Experiment #2 Section __________

This tutorial is designed to accompany the acids and bases experiment

Work in groups of three. When you have completed a problem or activity, explain your answers to your TA. Your TA will listen and offer advice, but he or she will not tell you if you are right or wrong. Please turn in this tutorial to your TA when you have complete all of the problems and activities on both sides of the paper. Thank you.

 

 

1. Identify the following solutions using one of these terms: strong acid, weak acid, strong base, weak base, acidic salt, basic salt, or neutral solution. Write an equation that supports your answer showing how H+, OH- or neither is generated

a. HNO3 (aq)

 

 

b. HNO2 (aq)

 

 

c. HONH2 (aq)

 

 

d. NaOH (aq)

 

 

 

2. If we change the pH of a HCl solution from pH = 6.00 to pH = 3.00. By what factor does this change the concentration of [H3O+] in the solution?

 

 

 

 

 

3. Which solution has the highest pH (largest number)? Which has the lowest pH?

a. 50.0 mL 0.0500 M nitric acid, HNO3 (aq)

 

 

b. 50.0 mL 0.0500 M nitrous acid, HNO2 (aq)

 

 

c. 50.0 mL 0.0500 M sodium hydroxide, NaOH (aq)

 

 

d. 50.0 mL 0.0500 M calcium hydroxide, Ca(OH)2 (aq)

 

 

Briefly explain.

 

 

 

Measuring the pH of Acid Solutions Using the pH Simulation. Work in groups of three.

Activity 1. Compare the pH of 100.0 ml of 0.500 M HCl pH = _____________ to the pH of 100.0 ml of 0.0500 M pH = ________________. Does this seem right to you?

 

 

 

Activity 2. Compare the pH of 50.0 mL 0.500 M nitric acid, HNO3 (aq) pH = ______________ to the pH of 50.0 mL 0.0500 M nitrous acid, HNO2 (aq) pH = _____________________.

Does this seem right to you?

 

 

 

Activity 4. Is there a relationship between the pH of a strong acid and the initial concentration of the acid? Plot a graph to show a relationship between initial concentration of [H3O+] (M) and pH. You will need to choose at least 5 different initial concentrations.

 

 

 Is there a relationship between the pH of a weak acid and the initial concentration (concentrated written on the label of the bottle of the acid) of the acid?

 Is there a relationship between the pH of a weak acid and the actual concentration of the acid in the solution?

Table 1 lists the pH measured for specific concentrations of acetic acid at 25°C.

labeled concentration [H3O+] (M)

0.75 M

0.50 M

å

0.10 M

0.010 M

pH

2.43

2.64

2.87

3.38

actual concentation [H3O+] (M)

 

 

Write a statement that tells the relationship between pH and the initial concentration of an acid solution.

 

What is the difference between the pH of strong acid and the pH of a weak acid at the same concentration. Explain why this is so.