If `3.01 xx 10^(28)` molecules are removed from 98 mg of `H_2SO_4,` then number of moles of `H_2SO_4` left are

Options

A. `0.5 xx 10^(-3)` mol
B. `0.1 xx 10^(-3)` mol
C. `9.95 xx 10^(-2)` mol
D. `1.66 xx 10^(-3)` mol

Answer

A

Explanation

`"No. of moles" H_(2)SO_(4) "in" 98 mg=(98 xx 10^(-3))/(98)`
`=1 xx 10^(-3)`
No. of moles of `3.01 xx 10^(20)` molecules of `H_(2)SO_(4)`
`=(3.01 xx 10^(20))/(6.02 xx 10^(23))=(1)/(2) xx 10^(-3)`
`"Moles of" H_(2)SO_(4) "left"=(1 xx 10^(-3)-0.5 xx 10^(-3))`
`=0.5 xx 10^(-3)`