1.

For a weak monobasic acid, if pK_(a)=4. then at a concentration of 0.01 M of the acid solution, the van't Hoff factor is

Answer»

1.01
1.02
`1.10`
`1.20`

Solution :`pK_(a)=4" means "K_(a)" for "HA=10^(-4)`
For weak acid, `HA hArr H^(+)+A^(-)`
`K_(a)=C ALPHA^(2)"(Ostwald's dilutio law)"`
`therefore""alpha=sqrt((K_(a))/(C))=sqrt((10^(-4))/(0.01))=10^(-1)=0.10`
`{:(,HA,hArr,H^(+),+,A^(-)),("Initial","1 mole",,,,),("Moles after ",1-alpha,,alpha,,alpha","):}`
`"dissoc.Total"=1+alpha`
`i=1+alpha=1+0.10=1.10`


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