Question

What volume of 2.5% (m/v) koh can be prepared from 125 ml of a 5.0% (m/v) koh solution?

Answer 1

Answer: 250 mL

Explanation: %(m/v) stands for mass by volume percentage. 2.5%(m/v) means 2.5 grams of a solute present in 100 mL of a solution.

The question asks to calculate the volume of 2.5%(m/v) KOH solution that can be prepared from 125 mL of a 5.0%(m/v) KOH solution.

It's a dilution problem and could easily be solved by using dilution equation:

`C_1V_1=C_2V_2`

where
`C_1` is the concentration before dilution and
`C_2` is the concentration after dilution. Similarly,
`V_1` is the volume before dilution and
`V_2` is the volume after dilution.

Let's plug in the values in the equation:

`5.0(125mL)=2.5(V_2)`

`V_2=(5.0(125mL))/(2.5)`

`V_2` = 250 mL

So, 250 mL of 2.5%(m/v) KOH solution can be prepared from 125 mL of 5.0%(m/v) KOH solution.

Answer 2

the volume of 2.5% m/v koh which can prepared from 125 ml of a 5% koh solution is calculated using the following formula

m1v1= m2 v2

M1= 5/100= 0.05
v1= 125
m2=2.5/100=0.025
V2=?
v2= m1v1/m2

=0.05 x125 /0.025=250 ml