Chem acid-base calculation急急急

The question is most probably as follows :
"0.72g of a metal M dissolved in 50 cm³ M sulphuric acid, which wasthen found to require 80 cm³ of 0.5 M N aOH forcomplete neutralization. If the oxidation state of the metal in the saltis+(II), what is its atomic mass?"

Solution :
Consider the neutralization of the excess H2SO4 with N aOH:
H2SO4 + 2N aOH → N a2SO4+ 2H2O
No. of moles of N aOH used = 0.5 x (80/1000) = 0.04 mol
No. of moles of H2SO4 reacted = 0.04 x (1/2) = 0.02 mol

Consider the reaction of H2SO4 and metal M :
M + H2SO4 → MSO4 + H2
No. of moles of H2SO4 used in the reaction = 1 x(50/1000) - 0.02 = 0.03 M
No. of moles of M = 0.03 M
Molar mass of M = 0.72/0.03 = 24 g/mol
Atomic mass = 24

2014-04-01 09:05:57 補充：
希望每一個發問者（自問自答者除外）都能夠自選最佳解答，因為只有發問者才知道哪個答案最適合自己。

M + H₂SO₄ → MSO₄ + H₂

H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O

No. of mole of NaOH = (0.5)(80/1000) = 0.04
No. of mole of H₂SO₄ reacted with NaOH = 0.04/2 = 0.02

No. of mole of H₂SO₄ in 50cm³ Y M H₂SO₄ = (Y)(50/1000) = 50Y/1000 = 0.05Y

No. of mole of H₂SO₄ reacted with metal M = 0.05Y - 0.02

No. of mole of metal M = 0.05Y - 0.02

atomic mass of metal M = 0.72 / (0.05 - 0.02)

IF YOU DON'T KNOW THE ORIGINAL CONCENTRATION Y. NOTHING CAN BE DONE.

2014-03-24 21:40:04 補充：
atomic mass of metal M = 0.72 / (0.05Y - 0.02)

2014-03-25 00:04:37 補充：
Put Y = 1 into

atomic mass of metal M = 0.72 / (0.05Y - 0.02)

= 0.72 / [0.05(1) - 0.02] = 24

2014-03-25 00:08:57 補充：
可能正如樓下 Adam 指出，你打題目時打漏了 "M"

M sulphuric acid 即濃度為 1M 的硫酸。

2014-03-29 10:57:10 補充：
希望你可以自己選最佳回答，你選那一個作為最佳並不重要，我只是不希望要由網友票選。