Choose a salt that creates an acidic, basic, and neutral solution. (Do all three
ID: 958496 • Letter: C
Question
Choose a salt that creates an acidic, basic, and neutral solution. (Do all three) Create a 0.5 M and 1.0 M solution of each salt and test the pH. After testing the pH, write the chemical equation that shows the ion's reaction with water, section 15.10 of Chang. Indicate whether the salt is acidic, basic, or neutral. Write the K_a or K_b expression for each ion that reacts with water. I have provided two examples. Describe the effect of increasing the concentration of the salts and explain why you think this effect is occurring.Explanation / Answer
(i): NaHSO4 creates acidic solution
Na2CO3 creates basic solution
NaCl creates neutral solution
(ii): You have to measure the pH of each solution
(iii): Reaction with H2O:
Acidic solution: HSO4-(aq) + H2O ----- > H2SO4 + OH-(aq)
Basic solution: CO32-(aq) + H2O ----- > HCO3-(aq) + OH-(aq)
HCO3-(aq) + H2O ------ > H2CO3 + OH-(aq)
neutral solution: no reaction
(iv): The solution of NaHSO4 is acidic due to formation of strong acid H2SO4 after hydrolysis.
The solution of Na2CO3 is basic due to formation of weak acid HCO3- and H2CO3 and OH-(aq).
NaCl solution is neutral
(v): HSO4-(aq) + H2O ----- > H2SO4 + OH-(aq)
Kb = [H2SO4]x[OH-(aq)] / [HSO4-(aq)]
CO32-(aq) + H2O ----- > HCO3-(aq) + OH-(aq)
Kb2 = [HCO3-(aq)]x[OH-(aq)] / [CO32-(aq)]
HCO3-(aq) + H2O ------ > H2CO3 + OH-(aq)
Kb1 = [H2CO3]x[OH-(aq)] / [HCO3-(aq)]
(vi): Acidic solution:
HSO4-(aq) + H2O ----- > H2SO4 + OH-(aq)
Kb = [H2SO4]x[OH-(aq)] / [HSO4-(aq)]
As we increase the concentration of HSO4-(aq), more and more product will form to keep the Kb constant. Hence the solution will become more acidic.
Basic solution:
CO32-(aq) + H2O ----- > HCO3-(aq) + OH-(aq)
Kb2 = [HCO3-(aq)]x[OH-(aq)] / [CO32-(aq)]
In a similar way as we increase the concentration of CO32-(aq), more and more product will form and the solution will become more basic.