Question

What is `[CaCl_2(aq)]` when a `10.0*g` mass of this salt is dissolved in water to give a `1.2*L` volume?

Answer 1

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

Explanation:

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

we set up the quotient `((10.0*g)/(110.98* g·mol^-1))/(1.2*L)` `=` `??*mol*L^-1` with respect to `CaCl_2`.

What is the concentration with respect to `Cl^-` ion.

Answer 2

The molarity of the solution would be `"0.75 M CaCl"_2"`.

Explanation:

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

The solute is calcium cloride, `"CaCl"_2"`. You have been given the mass of calcium chloride as 10.0 g, but you need moles.

To convert mass to moles, divide the given mass by the molar mass of calcium chloride, `"110.978 g/mol"`. https://pubchem.ncbi.nlm.nih.gov/compound/24854

`(10.0cancel"g")/(110.978cancel"g"/" mol")="0.0901 mol CaCl"_2"`

Substitute the number of moles into the molarity formula.

`"molarity"="0.901 mol"/"1.2 L"=0.75 "mol/L"="0.75 M CaCl"_2" solution"`