Question

If an `11.9*g` mass of potassium chloride is dissolved in `256*mL` of water, what is the concentration of the solution?

Answer 1

`"0.624 M"`

Explanation:

`"molarity" = ("moles of solute") / ("liters of solution")`

Its units are `"mol/L"`, or simply `"M"`.

Convert `"11.9 g KCl"` to moles:

`11.9 cancel("g KCl") xx ("1 mol KCl") / (74.55 cancel("g KCl")) = "0.160 mol KCl"`

Convert milliliters to liters:

`"256 mL = 0.256 L"`

`"molarity" = "0.160 mol" / ("0.256 L") = "0.624 M"`

Answer 2

`[KCl(aq)]=0.624*mol*L^-1`

Explanation:

`"Molarity"="Moles of solute"/"Volume of solution"`

And thus we can fill in this quotient....

`"Molarity"=((11.9*g)/(74.55*g*mol^-1))/(256*mL*xx10^-3*L*mL^-1)=0.624*mol*L^-1.`

Of course, we know in solution there are equimolar `K^+` and `Cl^-`..