Question

the molar concentration of 20g of NaOH present in 5 liters of solution is (atomic mass of Na =23)

Answer 1

Molarity

= Given mass * 100/ molecular mass* volume in litre

= 20*100/23*5

=400/23 M

Hope this helps!

Answer 2

We know that 1 Mole of NaOH weighs = (23 + 16 + 1) = 40grams.

Given that 20 grams of NaOH is present in 5 liters of solution.

⇒ If one Mole of NaOH weighs 40 grams then we need to find how many moles of NaOH makeup the weight of 20 grams

⇒ Number of moles which make up 20 grams of NaOH = (20 grams × 1 Mole)/(40 grams) = 0.5 moles.

We know that Molarity of a solution = (Number of Moles of Solute)/(Volume of Solution in litres)

Here the solute is NaOH and Volume of solution in liters is = 5

Molar Concentration of NaOH in the solution is = 0.5/5 = 0.1M