chem mc (已知答案,求解)

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2011-04-28 1:28 am

An iron nail is heated with concentrated sulphuric acid. which folling combinations is correct??
Gas given off Colour of solution formed
A.hydrogen pale green
B.htdrogen yellow
C.sulphur dioxide pale green
D. sulphur dioxide yellow
ANS:D
請問why is D and why isnot A B C

回答 (1)

sioieng

2011-04-28 4:10 am

✔ 最佳答案

The answer is: D. sulphur dioxide.... yellow

Iron reacts with common acid to give iron(II) and hydrogen.
Fe(s) + 2H^+(aq) → Fe^2+(aq) + H2(g)
Hydrogen is given off and the solution becomes pale green due to the presence of iron(II) ions.

However, concentrated sulphuric acid, on heating, is a rather strong oxidizing agent. The above reaction thus does not occur. Instead, a redox reaction occurs.
2Fe(s) + 6H2SO4(conc) → Fe2(SO4)3(aq) + 6H2O(l) + 3SO2(g)

Refer to the above equation. Sulphur dioxide gas is given off, and the solution becomes yellow due to the presence of iron(III) ions.

Therefore, the key is D. A, B and C are incorrect.

參考: sioieng

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