Question

Question #203c8

Answer 1

Understand the defenition of Molarity

Explanation:

Molarity= no of moles / volume of solution(in litres)
Hence here we have 0.5litre of 0.79M NaOH
So no of moles of NaOH in this will be
`0.5 * 0.79= 0.395` moles of NaOH
We know one mole of NaOH weighs 40 grams
Multiply this by no of moles to get the actual weight needed
So weight needed `= 40*0.395 grams`
Hope u find it helpful

Answer 2

`x` = 15.8g

Explanation:

molarity = `(n)/(volume( L)`; where n is the number of moles of the solute.

`n` = `x/(mm)`; where x is the required amount of NaOH and mm is the molar massof NaOH

therefore molarity, M = `x/(mm)` x `1000/(V(mL))`

`0.79` = `x/40` x `1000/500`

`x` = `0.79` x `20`

`x` = 15.8g