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

##### 1 Answer
Aug 19, 2017

You want the expression, $\text{moles of solute"/"volume of solution}$..

#### Explanation:

We ASSUME that $20 \cdot g$ of salt dissolves in $80 \cdot g$ 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 $80 \cdot m L$....

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

$\text{Moles of stuff"/"Volume of solution} = \frac{\frac{20 \cdot g}{58.44 \cdot g \cdot m o {l}^{-} 1}}{80 \times {10}^{-} 3 \cdot L} \cong 4 \cdot m o l \cdot {L}^{-} 1$