Question

How many moles are present in `"25 cm"^3` of `"0.2 M"` sodium hydroxide solution?

Answer 1

`5.0xx10^-3*mol` with respect to `NaOH`....

Explanation:

By definition...`"concentration"="moles of solute"/"volume of solution"`

And thus `"moles of solute"="concentration"xx"volume of solution"`

And....

`0.20*mol*L^-1xx25*cm^3xx10^-3*L*cm^-3=5.0xx10^-3*mol`

What is `pH` of this solution?

Answer 2

`"0.005 moles"`

Explanation:

Base equation

`"concentration" = "moles"/("volume" ("in dm"^3)`

Here

• concentration `= \ "0.2 M"`
• volume `= "25 cm"^3 = (25/1000) = "0.025 dm"^3`
• moles `=x`

Therefore

`0.2= x/0.025`

Multiply by `0.025` on both sides to leave `x` by itself

`- 0.2xx0.025=x`

`x = "0.005 moles" = 5xx 10^(-3) \ "moles"`