Please make sure to submit all of your answers at the same time. You cannot subm
ID: 866565 • Letter: P
Question
Please make sure to submit all of your answers at the same time. You cannot submit answers individually.
A solution with an unknown concentration of HNO2 is titrated to the equivalence point with KOH. What is the titration reaction?
HNO2 + KOH ? K+ + NO-2 + H2O
HNO2 + KOH ? KNO2 + OH-
HNO2 ? H+ + NO-2
What is the pH of the equivalence point?
acidic neutral basic
What species determines the pH at the equivalence point?
KOH
HNO
NO-2
50 mL of unknown concentration of HNO2 is titrated with 30.9 mL of 0.0523 M KOH. What is the unknown concentration of the original HNO2 solution?
Explanation / Answer
Reaction taking place is :
HNO2 + KOH ----> K+ + NO2- + H2O
Since KOH is a strong base while HNO2 is not a strong acid, thus at the equivalence point, the pH will be greater than 7, that is, basic
NO2- determines the pH at equivalence point, since it associates with water through following reaction :
NO2- + H2O ----> HNO2 + OH-
Moles of KOH required for titration = 0.0523*(30.9/1000) = 1.61*10-3
Thus, moles of acid present are also the same
Assuming the original solution's concentration as 'x', we get :
x*(50/1000) = 1.61*10-3
Solving, we get :
x = 0.0322 M