For the titration of 20.0 mL of 0.125 M nitrous acid HNO2 with 0.100 M sodium hy
ID: 992174 • Letter: F
Question
For the titration of 20.0 mL of 0.125 M nitrous acid HNO2 with 0.100 M sodium hydroxide, NaOH, answer the following questions and construct a titration curve.(please use pKa = 3.34 for nitrous acid).
a) What volume (in mL) of 0.100M sodium hydroxide is required to "neutralize" 20.0 mL of 0.125M nitrous acid?
b) What is the pH of the solution before any sodium hydroxide is added?
c) What is the pH at the half-stoichiometric or half-equivalence point?
d) What is the pH when 95% of the sodium hydroxide required to reach the stoichiometric point has been added
e) What is the pH at the stoichiometric point?
f) What is the pH when a 5% excess of the sodium hydroxid required to reach the stoichiometric point has been added?
g) What does the detailed graph look like?
Explanation / Answer
millimoles of HNO2 = 20.0 x 0.125 = 2.5
a)
at neutralization point
millimoles of acid = millimoles of base
2.5 = 0.1 x V
V = 25 mL
volume of NaOH = 25 mL
b)
pKa = 3.34
pH = 1/2 [pKa -logC]
pH = 1/2 [3.34 - log 0.125]
pH = 2.12
c)
at half-equivalence point pH = pKa
pH = 3.34
e)
at stoichiometric point only salt is formed
salt concentration = C = 2.5 / (25 + 20) = 0.06 M
pH = 7 + 1/2 [pKa + logC]
pH = 7 + 1/2 [3.34 + log 0.06]
pH = 8.04
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.