Question

Concentration Measurement of Calcium Chloride?

Hi,

Q: What is the concentration, in mol /L, of a solution formed by dissolving 28.0 g of calcium chloride in enough water to make 225 mL of solution?

I know the formula is c=nV, where c is concentration, n is the mass in grams and V is the volume in litres.

My question - Do you convert the 28g to 0.028kg or is it left as 28g?

This variation produces 6.3 and 0.0063 respectively. Which is it? Thanks

Answer 1

The molar concentration is 1.12 mol/L.

Explanation:

Step 1. Calculate the moles of `"CaCl"_2`

`n = 28.0 color(red)(cancel(color(black)("g CaCl"_2))) × "1 mol CaCl"_2/(110.98 color(red)(cancel(color(black)("mol CaCl"_2)))) = "0.2523 mol CaCl"_2`

Step 2. Calculate the litres of solution

`V = 225 color(red)(cancel(color(black)("mL"))) × "1 L"/(1000 color(red)(cancel(color(black)("mL")))) = "0.2250 L"`

Step 3. Calculate the molar concentration

`c = n/V = "0.2523 mol"/"0.2250 L" = "1.12 mol/L"`