Question

`"Solute 1"`, `"S1"`, has a molecular mass of `40.0*g*mol^-1`...what is...?

...what is `[S1]` if a `4*g` mass of this material is dissolved in a `200*mL` volume of solution?

Answer 1

By definition, `"concentration"-="amount of stuff"/"volume of solution"`

Explanation:

And typically, we use `"molarity"-="moles of solute"/"volume of solution"`

And thus `"concentration of S1"`

`=((4*g)/(40.0*g*mol^-1))/(200*mLxx10^-3*L*mL^-1)=0.50*mol*L^-1`

And note the dimensionality of this solution....

We cancel out common terms in the numerator and denominator....

`=((4*cancelg)/(40.0*cancelg*mol^-1))/(200*cancel(mL)xx10^-3*L*cancel(mL^-1))=0.5*(1/(mol^-1))/L=0.50*mol*L^-1`

Why? Because `1/x^-1=1/(1/x)=x` as required................