What are the percentage and molar concentrations of a #20g# mass of common salt dissolved in #80g# water?

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Answer 1 · 2017-08-19T15:30:32

You want the expression, #"moles of solute"/"volume of solution"#..

We ASSUME that #20*g# of salt dissolves in #80*g# of water; and thus our percentage concentration is.....

#(20*g)/(20*g*("salt")+80*g*("water"))xx100%=20%(w_"solute"/w_"solution")#

We FURTHER ASSUME that the volume of the solution is IDENTICAL to (or close enuff) to #80*mL#....

And this for molar concentration we take as usual the quotient......

#"Moles of stuff"/"Volume of solution"=((20*g)/(58.44*g*mol^-1))/(80xx10^-3*L)~=4*mol*L^-1#

What are the percentage and molar concentrations of a #20*g# mass of common salt dissolved in #80*g# water?