Answer:
The answer to your question is 19.19 g of CaCl₂
Explanation:
Data
mass of CaCl₂ = ?
volume = 0.247 l
[CaCl₂] 1 = 0.5 M
[CaCl₂] 2 = 1.2 M
Process
1.- Calculate the moles of CaCl₂ in the solution 1.2 M
Molarity = moles / volume
-Solve for moles
moles = Molarity x volume
-Substitution
moles = 1.2 x 0.247
moles = 0.2964
2.- Calculate the molar mass of CaCl₂
CaCl₂ = 40 + (35.5 x 2)
= 40 + 71
= 111 g
3.- Convert the moles to grams
111 g ---------------- 1 mol
x ----------------- 0.2964 mol
x = (0.2964 x 111)/1
x = 32.9 g
4.- Calculate the moles of the 0.5 M solution
moles = Molarity x volume
= 0.5 x 0.247
= 0.1235
-Convert to grams
111 g ---------------- 1 mol
x ----------------- 0.1235 moles
x = (0.1235 x 111) / 1
x = 13.7085
5.- Subtract the grams to find the mass needed.
Mass = 32.9 - 13.7085
= 19.19 g of CaCl₂
6.- Conclusion
We need to add 19.19 g of CaCl₂ to raise the concentration to 1.2.
