How many liters of a 0.2 M NaOH solution are needed in order to have 1.0 moles of NaOH?

1 Answer
anor277
Oct 17, 2016

#"5 litres"# of solution are required.

Explanation:

#"Concentration"# #=# #"Moles of solute"/"Volume of solution"#.

Given that the typical units of #"concentration"# are #mol*L^-1#, to get #"concentration"# or #"amount of moles"# or #"volume of solution"# we just have to take the appropriate product or quotient.

We want #1.0*mol# #NaOH#:

this the product #"Volume of solution "xx" Concentration"#.

So we need the quotient: #"Moles of solute"/"Concentration"# #=# #(1.0*cancel(mol))/(0.2*cancel(mol)*L^-1)# #=# #5*L#.

(i.e. #1/(1*L^-1)=1*L)#

Note that we go to such trouble in including the units in these calculations as an extra check on our arithmetic. Sometimes you ask yourself should I divide or should I multiply. Dimensional analysis answers our question. We wanted an answer in #"litres"#, and we got one. This persuades us that we did the calculation right.

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