7.1.2: Practice Mole Calculations
 Page ID
 236040
Molar Mass, Gram to Mole, Mole to Gram
Exercise \(\PageIndex{1}\)
How many moles of Ca_{3}(PO_{4})_{2} are in 57.82 grams?
 Molar Mass

Ca_{3}(PO_{4})_{2 }= \(\dfrac{310.18 g}{mol}\)
 Answer

0.1864 moles
How many grams of Zn(OH)_{2} are in 3.67 moles?
 Molar Mass

Zn(OH)_{2 }= \(\dfrac{99.41 g}{mol}\)
 Answer

365 grams
How many moles of Mg(NO_{3})_{2} are in 487.6 grams?
 Molar Mass

Mg(NO_{3})_{2 }= \(\dfrac{148.33 g}{mol}\)
 Answer

3.287 moles
Using Avogadro's Number
Exercise \(\PageIndex{1}\)
How many molecules of H_{2}O are in 0.0643 grams of H_{2}O?
 Answer

0.0643 grams of H_{2}O is equal to 0.00357 moles, which is 2.15 x 10^{21} molecules
How many moles of Au is equal to 4.77 x 10^{27} Au atoms?
 Answer

7920 moles
Using Formula Subscripts
Exercise \(\PageIndex{1}\)
How many moles of NH_{3} would contain 8.18 moles of H atoms?
 Answer

2.73 moles NH_{3}
How many Br atoms are in 0.453 moles of CBr_{4}?
 Answer

1.09 x 10^{24} Br atoms
Mixed
Exercise \(\PageIndex{1}\)
How many moles of Ca(OH)_{2} are in 5.62 g of Ca(OH)_{2}?
 Answer

0.0758 mol Ca(OH)_{2}
How many moles of O are in this amount?
 Answer

0.152 mol O
How many individual atoms of O are in this amount?
 Answer

9.13 x 10^{22} O atoms
Exercise \(\PageIndex{1}\)
How many moles of C_{4}H_{8}O_{2} can be made with 18.5 mol C?
 Answer

4.63 moles of C_{4}H_{8}O_{2}
Exercise \(\PageIndex{1}\)
How many grams of C_{4}H_{8}O_{2} can be made with 2.86 x 10^{21} C atoms? (Hint: how many moles of C is this?)
 Hint

0.00475 mol C
 Answer

0.00119 mol C_{4}H_{8}O_{2} which is 0.105 g C_{4}H_{8}O_{2}