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titration

2009-02-16 10:00 am

X is a trivalent metal .When treated with hydrochloric acid ,X(s) gives hydrgen ,while its oxide X2O3(s)
undergoes neutralisation.

a) Write the chemical equation of the reaction of X(s) with HCl (aq) and that of X2O3(s) with HCl(aq).

b) 16.5g of a mixture of X(s) and X2O3(s) is allowed to react with 6 M HCl(aq). 95.4 cm^3 of the acid is
required for both the metal and its oxide to undergo complete reaction.

Deduce respectively the greatest possible value and the smallest possible value of the relative atomic mass
of X.

更新1:

我仲想知咩係trivalent metal?

回答 (1)

老爺子

2009-02-16 4:11 pm

✔ 最佳答案

a)
2X + 6HCl → 2XCl3 + 3H2
X2O3 + 6HCl → 2XCl3 + 3H2O

b)
Let the relative atomic mass of X be y.

No. of moles of HCl used = 6 x (95.4/1000) = 0.5724 mol

When the sample contains almost entirely X.
Mole ratio X : HCl = 2 : 6 = 1 : 3
No. of moles of X used = 0.5724/3 = 0.1908 mol
Molar mass of X = 16.5/0.1908 = 86.5 g /mol
Relative atomic mass of X = 86.5

When the sample contains almost entirely X2O3.
Mole ratio X2O3 : HCl = 1 : 6
No. of moles of X used = 0.5724/6 = 0.0954 mol
Molar mass of X = 16.5/0.0954 = 173 g /mol
Relative atomic mass of X = (173 – 16 x 3)/ 2 = 62.5

The greatest possible value of the relative atomic mass of X is 86.5,
and the smallest possible value of the relative atomic mass of X is 62.5.
==

2009-02-16 08:12:46 補充：
A trivalent metal forms positive ion with 3 positive charges.

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