# 7.1.2: Practice Mole Calculations

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#### Molar Mass, Gram to Mole, Mole to Gram

Exercise $$\PageIndex{1}$$

How many moles of Ca3(PO4)2 are in 57.82 grams?

Molar Mass

Ca3(PO4)= $$\dfrac{310.18 g}{mol}$$

0.1864 moles

How many grams of Zn(OH)2 are in 3.67 moles?

Molar Mass

Zn(OH)= $$\dfrac{99.41 g}{mol}$$

365 grams

How many moles of Mg(NO3)2 are in 487.6 grams?

Molar Mass

Mg(NO3)= $$\dfrac{148.33 g}{mol}$$

3.287 moles

Exercise $$\PageIndex{1}$$

How many molecules of H2O are in 0.0643 grams of H2O?

0.0643 grams of H2O is equal to 0.00357 moles, which is 2.15 x 1021 molecules

How many moles of Au is equal to 4.77 x 1027 Au atoms?

7920 moles

#### Using Formula Subscripts

Exercise $$\PageIndex{1}$$

How many moles of NH3 would contain 8.18 moles of H atoms?

2.73 moles NH3

How many Br atoms are in 0.453 moles of CBr4?

1.09 x 1024 Br atoms

#### Mixed

Exercise $$\PageIndex{1}$$

How many moles of Ca(OH)2 are in 5.62 g of Ca(OH)2?

0.0758 mol Ca(OH)2

How many moles of O are in this amount?

0.152 mol O

How many individual atoms of O are in this amount?

9.13 x 1022 O atoms

Exercise $$\PageIndex{1}$$

How many moles of C4H8O2 can be made with 18.5 mol C?

4.63 moles of C4H8O2

Exercise $$\PageIndex{1}$$

How many grams of C4H8O2 can be made with 2.86 x 1021 C atoms?  (Hint: how many moles of C is this?)

Hint

0.00475 mol C