What is the pH at the equivalence point in the titration of a 23.6 mL sample of a 0.385 M aqueous hydrocyanic acid solution with a 0.318 M aqueous sodium hydroxide solution?
HCN + NaOH ---> NaCN + H2O
at equivalence point , Formation of salt(NaCN) takes place
1 mole HCN = 1 mol NaOH
so that, pH depends on salt
No of mol of HCN reacted = 23.6*0.385 = 9.086 mmole
volume of NaOH reacted = 9.086/0.318 = 28.57 ml
concentration of salt = 9.086/(23.6+28.57) = 0.174 M
pH at equivalence point = 7+1/2(pka+logC)
pka of HCN = 9.2
= 7+1/2(9.2+log0.174)
= 11.22
Get Answers For Free
Most questions answered within 1 hours.