Be sure to answer all parts. Calculate the amount of water (in grams) that must

Question

Be sure to answer all parts.

Calculate the amount of water (in grams) that must be added to each of the following substances to produce the indicated solution.

(a) 1.40 g of urea (NH2)2CO in the preparation of a 12.3 percent by mass solution:

g

(b) 22.5 g of MgCl2 in the preparation of a 5.9 percent mass solution: Be sure to answer all parts.

Calculate the amount of water (in grams) that must be added to each of the following substances to produce the indicated solution.

(a) 1.40 g of urea (NH2)2CO in the preparation of a 12.3 percent by mass solution:

g

(b) 22.5 g of MgCl2 in the preparation of a 5.9 percent mass solution:

Explanation / Answer

a) % by mass = (mass of solute / mass of solution) x 100

12.3 = (1.40 / mass of solution) x 100

0.123 = 1.40 / mass of solution

mass of solution = 11.4 g

mass of water = 11.4 - 1.40 = 10.0 g

mass of water = 10.0 g

b) % by mass = (mass of solute / mass of solution) x 100

5.9 = (22.5 / mass of solution) x 100

0.059 = 22.5 / mass of solution

mass of solution = 381.3 g

mass of water = 381.3 - 22.5

mass of water = 358.8 g

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