f.4 chem計數

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2013-03-13 10:47 pm

0.720g of a metal X dissolved completely in 50.0 cm^3 of 1.00 M sulphuric acid, which was then found to require 80.0 cm^3 of 0.500 M sodium hydroxide solution for complete neutralization. If the oxidation state of the metal in the salt is +II, what is its atomic mass?

回答 (1)

andrew

2013-03-14 5:58 am

✔ 最佳答案

Consider the neutralization of the excess H2SO4 byusing NaOH :
H2SO4 + 2NaOH → Na2SO4+ 2H2O

No. of moles of NaOH = 0.500 x (80.0/1000) = 0.0400 mol
No. of moles of H2SO4 reacted with NaOH = 0.0400 x (1/2)= 0.0200 mol

Consider the reaction of metal X with H2SO4 :
X + H2SO4 → XSO4 + H2

Total no. of H2SO4 added = 1.00 x (50.0/1000) = 0.0500mol
No. of moles of H2SO4 reacted with X = 0.0500 - 0.0200 =0.0300 mol
No. of moles of X = 0.0300 mol
Molar mass of X = 0.720/0.0300 = 24.0 g/mol
Atomic mass of X = 24.0

參考: andrew

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