Calculating Mass to Moles and Moles to Mass. This triangle is very important: m n gfm Where: m = mass of substance (grams). n = number of moles of substance (moles) gfm = gram formula mass of substance (grams). Example: How many moles are in 8g of magnesium oxide (MgO)? Write down what you know: Number of moles n = ? Mass of substance m = 8g Remember you can always work out the gfm of any substance using your data booklet once you know its name/formula. gfm of MgO = (1 x Mg) + (1 x O) = (1 x 24.5) + (1 x 16) = 24.5 + 16 = 40.5g Number of moles, n = _m_ = _8_ = 0.196 mols or 0.2 moles gfm 40.5 Using the triangle above: Calculate the mass of: 2 moles of calcium carbonate. 0.1 moles of nitric acid. Calculate the number of of: 10g of calcium carbonate. 10.6g of sodium nitrate. 7.5g of Iron(iii) oxide
Calculating Mass to Moles and Moles to Mass. This triangle is very important: m n gfm Where: m = mass of substance (grams). n = number of moles of substance (moles) gfm = gram formula mass of substance (grams). Example: How many moles are in 8g of magnesium oxide (MgO)? Write down what you know: Number of moles n = ? Mass of substance m = 8g Remember you can always work out the gfm of any substance using your data booklet once you know its name/formula. gfm of MgO = (1 x Mg) + (1 x O) = (1 x 24.5) + (1 x 16) = 24.5 + 16 = 40.5g Number of moles, n = _m_ = _8_ = 0.196 mols or 0.2 moles gfm 40.5 Using the triangle above: Calculate the mass of: 2 moles of calcium carbonate. 0.1 moles of nitric acid. Calculate the number of of: 10g of calcium carbonate. 10.6g of sodium nitrate. 7.5g of Iron(iii) oxide
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