A soluction of 100 mL of 0.2 M NH3 is titratedwith 50 mL of 0.5 M HNO3. What is the

Question

pH of the resulting solution? Kb for NH3 is
1.8 × 10−5
1. 5.30
2. 1.00
3. 1.48
4. 10.3

Answer 1

NH3 + HNO3 ==> NH4NO3 + H2O
millimols NH3 = 100 x 0.2 = 20
mmols HNO3 = 50 x 0.5 = 25
So you've added enough HNO3 to neutralize all of the NH3 and have an excess of 5 mmols HNO3 left. That's in 100 + 50 = 150 mL
M HNO3 = mmols/ml = ?M