Find the total percentage of magnesium in magnesium nitrate crystals, Mg(NO₃)₂.6H₂O

[Mg = 24; N = 14; O = 16 and H = 1]

Molecular weight of Mg(NO₃)₂.6H₂O = 24 + 2[14 + 3(16)] + 6[2(1) + 16]
= 24 + 2[14 + 48] + 6[18]
= 24 + 2(62) + 108
= 24 + 124 + 108 = 256 g

256 g of magnesium nitrate crystals contains 24 g of magnesium

∴ 100 g of magnesium nitrate crystals will contain = $\dfrac{24}{256}$ x 100 = 9.375% = 9.38%

Hence, percentage of magnesium in magnesium nitrate crystals is 9.38%