a) How many grams of CaCl2 are needed to make 213.8 g of a solution that is 38.5

Question

a) How many grams of CaCl2 are needed to make 213.8 g of a solution that is 38.5% (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 139 mL of isopropyl alcohol in 745 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 685 mL of a 38.0% (w/v) sucrose solution?

Explanation / Answer

a)

mass percent % = mass of solute/ total mass of solution * 100

mass of CaCl2 are required   = 213.8*38.5/100 = 82.313 grams

so that ,

By dissolving 82.313 grams of cacl2 in

(213.8-82.313) = 131.487 grams of water.we can get 38.5% (m/m) calcium chloride in water

b)

volume percent % = volume of solute/ total volume of solution * 100

              = 139/(745+139)*100   = 15.72%

c)

mass of solute per 100 mL of solution = mass of sucrose / volume of solution*100

38 = (w/685)*100

w = mass of sucrose   = 260.3 grams

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