Mole calculations working out 2

1000 g of C₁₂H₂₂O₁₁ (sugar)

C = 12, H = 1, O = 16

C₁₂H₂₂O₁₁ = (12 × 12) + (22 × 1) + (11 ×16) = 342 g mol^-1

1000 g of C₁₂H₂₂O₁₁ = 1000/342 = 2.92 mol (to 3 sig. figs.)

568 g (1 pint) of water

H = 1, O = 16

H₂O = (2 × 1) + 16 = 18 g mol^-1

568 g of H₂O = 568/18 = 31.6 mol (to 3 sig. figs.)

0.174 g of sodium carbonate

sodium carbonate = Na₂CO₃ - if you got this wrong check the section on ionic formulae

Na = 23, C = 12, O = 16

Na₂CO₃ = (2 × 23) + 12 + (3 × 16) = 106 g mol^-1

0.174 g of Na₂CO₃ = 0.174/106 = 0.00164 mol (to 3 sig. figs.)

4.28 g of cobalt(II) chloride-6-water

cobalt(II) chloride-6-water = CoCl₂.6H₂O - if you got this wrong check the section on ionic formulae

H = 1, O =16

H₂O = (2 × 1) + 16 = 18 g mol^-1

Co = 59, Cl = 35.5, H₂O = 18

CoCl₂.6H₂O = 59 + (2 × 35.5) + (6 × 18) = 238 g mol^-1

4.28 g of CoCl₂.6H₂O = 4.28/238 = 0.0180 mol (to 3 sig. figs.)

1.00 mg of C₁₆H₁₈O₄N₂S (penicillin)

C = 12, H = 1, O = 16, N = 14, S = 32

C₁₆H₁₈O₄N₂S = (16 × 12) + (18 × 1) + 4 × 16) + (2 × 14) + 32 = 334 g mol^-1

mg = milligram = 1 × 10^-3 g

1.00 mg of C₁₆H₁₈O₄N₂S = 1 × 10^-3/334 = 2.99 × 10^-6 mol (to 3 sig. figs.)