1992 chem mc q11

2010-03-03 2:08 am

The following substance were burnt in oxygen and the products were mixed with water.Which of these substance would produce a resulting soltion with the highest pH?
A calcium
B Iron
Csulphur
D.carbon
Why is not B the answer?

回答 (1)

Prof. Physics

2010-03-03 2:48 am

✔ 最佳答案

The answer is A.

For A, it will turn to calcium hydroxide while it is an alkali, which gives the pH value of the solution higher than 7.

2Ca(s) + O2(g) + 2H2O(l) → 2Ca(OH)2 (aq)

For B, it will give iron (III) oxide, but it is a base, not soluble in water. So, it will have the pH value of 7 which indicates it is neutral.

For C and D, they will give aqueous sulphur dioxide and carbonate respectively. They are acidic and so they give the solution a pH value lower than 7.

So, A is the answer.

參考: Physics king

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