幫幫手 計算的! 10 marks

Question

1.an oxide of a metal Xhas the empirical formula of XO.when 97.2g of the oxide is heated strongly, t decomposes to give 90.0g of the meat.what is the relative atomic mass of X?(relative atomic mass of O is 16)

Answer 1

In 97.2 g of XO,
Mass of X = 90.0 g
Mass of O = 97.2 – 90.0 = 7.2 g

No. of moles of O = 7.2/16 = 0.45 mol
In XO, mole ratio X : O = 1 : 1
No. of moles of X = 0.45 mol

The mass of 0.45 mol of X is 90.0 g
Molar mass of X = (Mass)/(No. of moles) = 90.0/0.45 = 200 g mol-1

2007-01-01 17:09:59 補充：
Relative atomic mass of X = 200

Answer 2

Because atomic mass of O is 16 and 7.2g of oxygen is gone after the oxide is heated up, therefore 7.2/16 mole of oxygen is gone.

Now the ratio of X to O is 1:1 in the metal oxide, we therefore know that 7.2/16 mole of X is equal to 90g.

Therefore the atomic mass of X is 90 x 16 / 7.2.