A fertiliser sample contains 40% ammonium sulfate, (NH4)_2SO4, by mass; the remainder has no nitrogen. The mass percentage of nitrogen in the sample is (H = 1, N = 14, O = 16, S = 32)

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A fertiliser sample contains $40%$ ammonium sulfate, $(NH X_{4})_{2} SO X_{4}$ , by mass; the remainder has no nitrogen. The mass percentage of nitrogen in the sample is (H = 1, N = 14, O = 16, S = 32)

Molar mass of (NH4)2SO4 = 36 + 32 + 64 = 132; N = 28 g, so pure salt has 21.21% N. The sample has only 40% salt: 21.21 x 0.40 = 8.48%.