The copper hydroxide was heated to form water and copper oxide (2).

The copper hydroxide was heated to form water and copper oxide (2). Determine the mass of copper oxide if copper hydroxide contains 12% impurities.

1) Determine the mass of impurities in the “dirty” copper hydroxide, for which we make the proportion:

174 g of “dirty” copper hydroxide is 100%

x g make up 12% of impurities,

Consequently:
174 g – 100%
x g – 12%.

x = 174 * 12: 100 = 20.88 (g) is the mass of impurities.

2) This means that the mass of pure copper hydroxide is: Mass of “dirty” copper hydroxide – Mass of impurities = 174 g – 20.88 g = 153.12 g.

2) we determine the mass of the formed copper oxide by composing the reaction equation. Let us write under the formulas of substances their relative molecular weights (below) and the masses actually participating in the reaction (above):

Cu (OH) 2 -> CuO + H2O;

Now you can make the proportion:
153.12 – 98
x – 80.

Therefore, x = 153.12 * 80: 98 = 125 g.