Equilibrium strong/weak acid calculations

Question

Use the following information to answer the first THREE questions.

 

Nitric acid and nitrous acid are two acids associated with acid deposition.   

 

Acid	pH of 0.10 mol/L solution
HNO3(aq)	1.0
HNO2(aq)	2.2

Question 1 (1 point)

 

Use the information above to identify which of the acids is a strong acid, and which is a weak acid. Support your reasoning without the use of a calculation.

Question 2 (1 point)

Support your answer to the last question, using a calculation.  You must show ALL your work to get full marks.

 

Question 3 (1 point)

 

Identify one other difference that you would expect if you tested these two solutions. Include the name of the test, the expected results for each solution, and the reasoning for the expected difference.

Answer 1

A strong acid is one that dissociates completely whereas a weak acid is one that only partially dissociates. This means that at equal concentrations the pH of the strong acid will be lower than that of the weak acid because more H+ ions will be produced.

1). HNO3 is the strong acid and HNO2 is the weak acid

2). HNO3 ==> H+ + NO3-. At 0.1 M, [H+] = 0.1 M and pH = -log 0.1 = 1. Since the pH of 0.1 M HNO2 is greater than 1, this means it doesn't dissociate completely.

3). One could look at electrical conductivity of each solution. Not sure this test has a name but it is looking at whether or not the substance is a strong or weak electrolyte. HNO3 will conduct a current better than HNO2 at the same concentration.