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