Question

molecular mass of koh is 56 what is molarity of solution prepared by dissolving 84.0 gram of pure koh in 500ml of solution

Answer 1

We calculate the Molarity by the following formula - 

Molarity = Number of Moles of solute/Volume of solution (in litre)

A solution is made up of little components of solute dissolve in the solvent.

Number of Moles = Given Mass/Molecular Mass

The Relationship between 2 solutions with same number of Moles is given as

C₁V₁ = C₂V₂

Where C and V are concentration and volume of solution respectively.

In this question we are given - Molecular Mass of KOH = 56g/mole Volume = 500ml

Given Mass = 84g

Number of moles = 84g / 56g / mole = 1.5 mole

Volume = 500 / 1000 = 0.5 litre

(We divide by 1000 to convert it into litres since 1litre = 1000ml).

Molarity = 1.5 mole / 0.5 litre = 3 mole / litre or 3M