Question #203c8

2 Answers
Jan 18, 2018

Answer:

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

Jan 18, 2018

Answer:

#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