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

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:

where is the concentration before dilution and is the concentration after dilution. Similarly, is the volume before dilution and is the volume after dilution.

Let's plug in the values in the equation:

= 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.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.