Question

When an aqueous solution at room temperature is analyzed, the [H+] is found to be 2.0 × 10−3 M. What is the [OH−]?

A. 5.0 × 10−12 M
B. 2.0 × 10−11 M
C. 4.0 × 10−6 M
D. 5.0 × 10−11 M

Answer 1

the answer would be A. 5.0x10-12m

Answer 2

Answer : The correct option is, (A)
`5.0* 10^(-12)M`

Step-by-step explanation:

First we have to calculate the pH.

`pH=-\log [H^+]`

`pH=-\log (2.0* 10^(-3))`

`pH=2.69`

Now we have to calculate the pOH.

`pH+pOH=14\\\\pOH=14-pH\\\\pOH=14-2.69=11.31`

Now we have to calculate the
`OH^-` concentration.

`pOH=-\log [OH^-]`

`11.31=-\log [OH^-]`

`[OH^-]=5.0* 10^(-12)M`

Therefore, the
`OH^-` concentration is,
`5.0* 10^(-12)M`