(a) How many grams of CaCl2 are needed to make 993.4 g of a solution that is 31.

Question

(a) How many grams of CaCl2 are needed to make 993.4 g of a solution that is 31.5% (m/m) calcium chloride in water? Note that mass is not technically the same thing as weight, but (m/m) has the same meaning as (w/w).

How many grams of water are needed to make this solution?

(b) What is the volume percent % (v/v) of an alcohol solution made by dissolving 111 mL of isopropyl alcohol in 763 mL of water? (Assume that volumes are additive.)

(c) The mass of solute per 100 mL of solution is abbreviated as % (m/v). (The abbreviation % (w/v) is also common.) How many grams of sucrose are needed to make 725 mL of a 30.0% (w/v) sucrose solution?

Explanation / Answer

(a) total mass of solution = 993.4 g

31.5% of 993.4 = 312.91 g

So we would need, 312.91 g of CaCl2

mass of water reuired = 993.4 - 312.91 = 680.49 g

(b) % v/v of isopropyl alcohol solution = [111 ml/(111 + 763) ml] x 100 = 12.70 %

(c) 30% w/v means 30 g in 100 ml

So mass of sucrose (30% w/v) in 725 ml would be = 217.5 g

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