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Question
Find the percentage of oxygen in magnesium nitrate crystals [Mg(NO3).6H2O].
Solution
The molecular mass of [Mg(NO3).6H2O] = 24 + (2 × 62) + 6 × 18
= 24 + 124 + 108
= 256
Mass due to oxygen = (2 × 48) + (6 × 16)
= 96 + 96
= 192
% of oxygen = `192/256 xx 100`
= 75%
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