Copper sulphate reacts with sodium hydroxide to form a blue precipitate of copper hydroxide and sodium sulphate. In an experiment, 15.95 g of copper sulphate reacted with 8.0 g of sodium hydroxide to form 9.75 g of copper hydroxide and 14.2 g of sodium sulphate. Which law of chemical combination is illustrated by this data? Give reason for your choice.

Here are the equations for copper sulphate solution reacting with sodium hydroxide solution:

copper sulfate + sodium hydroxide copper hydroxide + sodium sulfate


CuSO4 + 2NaOH Cu(OH)2 + Na2SO4


(15.95g + 8g 9.75g + 14.2g)


23.95g = 23.95g


As all the reactants and products remain in the sealed reaction container then it is easy to show that the total mass is unchanged. This data shows the law of conservation of mass.


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