# Buffer solutions

1. Jul 5, 2016

### TT0

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
From what I know, to make buffer solutions you need a weak acid or base and it's salt. Non of the options has this. What am I missing?

Cheers!

2. Jul 5, 2016

### Staff: Mentor

What is left after the reaction?

3. Jul 6, 2016

### TT0

For reaction 1, the products are: Cl-, NH4+, NH3, H+ (as HCl is strong acid while ammonia is weak base)
For reaction 2, the products are: Na+, H2O, NO2- (NaOH is strong while nitrous acid is weak. No HNO2 because the H+ will react to form water so equilibrium will shift to the right in equilibrium HNO2 → H+ + NO2-)
For reaction 3, the products are: NH3, NH4+, HNO2, NO2- (both are weak)

Reaction 3 is probably creates a buffer solution as they can accept or donate protons and the equilibrium will shift.
If acid was added to reaction 2, the NO2- will turn to nitrous acid but if base was added, nothing will happen, so not a buffer solution.
If acid was added to reaction 1, the equilibrium NH3 + H+ ↔ NH4+ will shift to the right and if base was added, the equilibrium will shift to the left so it is a buffer solution.

Are my explanations correct?

Cheers!

4. Jul 6, 2016

### Staff: Mentor

Nope, you need a comparable amounts of conjugate acid and base for the buffer to exist.

5. Jul 8, 2016

### TT0

I see, I change my mind on reaction 2. There will be around 0.5 M of HNO2 and NO2- so it will be a buffer solution. So then the answer is E?

Cheers!

6. Jul 9, 2016

### Staff: Mentor

What is present after the reaction in the 3rd mixture?

7. Jul 12, 2016

### TT0

NH3, NH4+, HNO2, NO2-

8. Jul 12, 2016

### Staff: Mentor

In what (approximate at least) concentrations?