Question

HA is a weak acid. The pH of 0.1 M HA solution is 2. What is the degree of dissociation `(alpha)` of HA ?
A. 0.5
B. 0.2
C. 0.1
D. 0.301

Answer 1

Correct Answer - C
`pH=2` means `[H^(+)] =10^(-2)M`
`{:(,HA,hArr,H^(+),+,A^(-)),("Initial",cM,,,,),("At eqm.",c(1-alpha)M,,calpha,,calpha):}`
`:. [H^(+)]=c alpha` or `alpha=([H^(+)])/(c )`
`alpha=(10^(-2))/(10^(-1))=10^(-1)=0.1`