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10 mg of magnesium metal, Mg, and 30 ml of hydrochloric acid, HCl, are added to

ID: 718950 • Letter: 1

Question

10 mg of magnesium metal, Mg, and 30 ml of hydrochloric acid, HCl, are added to 300 ml of water, H2O. After the hydrogen has evolved, the following was produced: 0.000829 g of hydrogen gas, H2; 2.157657 g of hydrogen chloride, HCl; 0.039173 g of magnesium chloride, MgCl2; and 330.0000 g of water, H2O.

There is a one to one relationship between the number of moles of hydrogen gas evolved and the moles of Magnesium metal consumed in the reaction, therefore moles of H2 evolved = moles Mg consumed and the atomic weight of Mg = weight of Mg consumed/moles of H2 evolved.

What is theamount og H2 evolved?

What is the amount of Mg consumed?

What is the atomic weight of Mg?

Explanation / Answer

Mg + HCl ---> MgCl2 + H2 The amount of H2 evolved = 0.000829/ 2 = 0.0004145 moles the amount of Mg consumed = 10^-3 gram the atomic weight of Mg = 10^-3/0.0004145 = 24.125 gram /mole see as Mg is very reactive in nature all of it will react with the HCl.