The number of hydroxyl ions in ` 10 cm^(3)` of 0.2 M HCl solution is

Options

A. `3 xx10^(-12)`
B. ` 6.023 xx10^(12)`
C. ` 3 xx 10^(8)`
D. ` 3 xx 10^(10)`

Answer

C

Explanation

0.2 M HCl =0.2 mole of HCl` // 1000 cm^(3) ` of solution
`=0.2xx 10^(-2) ` moles of HCl `// 10 cm^(3)` of solution
Now, `0.2 xx 10^(-2)= 2 xx 10^(-3)` mole HCl ` = 2 xx 10^(-3)` moles of `[H^(+)]` ion
Now, `k_(w) = [H^(+)][OH^(-)]=10^(-14)`
`:.[OH^(-)] =10^(-14) //2 xx10^(-3) = 0.5 xx 10^(-11) ` moles
No. of `[OH^(-)] = 0.5 xx 10^(-11) xx 6.022 xx 10^(23) = 3 xx 10^(12) ` ions