If the density of copper is 8.92 x 10^3 g/L and the density of magnesium is 1.74 x 10^3 g/L, what mass of magnesium occupies the same volume as 100.0 g of copper?
Density is mass per unit volume, so for the copper we have
8.92*10^3= 100/V so V = 100/(8.92*10^3) = 1/89.2 L
For magnesium: 1.74*10^3 = M/(1/89.2) so M = 1.74*10^3/89.2 ≈ 19.51 g
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