How many `mL` of a solution of concertration `100 mg Co^(2+)` per `mL` is needed to prepare `10 mL` of a solution of concentration `20 mg Co^(2+)` per `mL`.

Answer

B

Explanation

`M_(1) V_(1) = N_(2) V_(2)` (Atomic weight of `Co = 59.93 g)`
`(100 mg)/(cancel(58.93 mg)) xx V_(1) = (20 mg)/(cancel(58.93 mg)) xx 10 mL`
`V_(1) = (20 xx 10)/(100) = 2 mL`