Solution. Read the problem carefully and determine the desired quantity.

Grams of CuSO4.H2O.

Calculate the amount of the anhydrous form needed.

1 dL

10.0 g

100 mL X -------- X -------- = 10.0 g

100 mL

1 dL

Calculate the gram molecular weight of each substance. (**NOTE: **You will

learn more about gram molecular weights and moles in Lesson 3.)

(1)

List each element in a column.

(2)

Write the atomic weight of each element. (See Appendix C.)

(3) Multiply the weight of each element by the number of that element in the

chemical formula. For example, if there are 2 atoms of hydrogen present in the formula,

multiply the weight of hydrogen by two.

(4) Sum the weights to obtain the total weight, and express the total weight

in grams/mole.

CuSO4 (anhydrous)

Cu 63.5 X 1 = 63.5

S

32.1 X 1 = 32.1

O 6.0 X 4 = + 64.0

159.6 g/mole

CuSO4.H2O (hydrate)

Cu

63.5 X 1 = 63.5

S

32.1 X 1 = 32.1

O

6.0 X 4 = 64.0

H

1.0 X 2 = 2.0

O

6.0 X 1 = + 16.0

177.6 g/mol

If the amount of anhydrous salt needed is now multiplied by the ratio of the

molecular weights of the hydrate to anhydrate the desired results will be obtained.

177.6 g/mol CuSO4.H2O

10.0 g CuSO4 X ---------------------- = 11.1 g CuSO4.H2O

159.6 g/mol CuSO4

MD0837

2-12

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