chem難題 - Ans.fyi 參考答案

chem難題

2007-07-11 11:55 pm

Beaker 1 contains 100cm^3 of 0.10M HCl and Mg ribbon
Beaker 2 contains 200cm^3 of 0.0010M HCl and Mg ribbon
Beaker 3 contains 200cm^3 of 0.10M CH3COOH and Mg ribbon

a)Point out one mistake. Explain the mistake and suggest corresponding corrections
b) Suppose mistake in (c) is corrected.
i) Arrange the acids in order if increasing initial rate of reaction with Mg. Explain your ANS.
ii) Suggest TWO factors affecting the pH of an acids.

回答 (1)

Fergus Chau

2007-07-12 12:51 am

✔ 最佳答案

a. Beaker should not be used. It is because concentration of the solution is accurate (0.10 M). Therefore, a more accurate instrument should be used. For example, 25.00 cm^3 pipette. This pipette is used to measure the volume of the solution.

b. 1. The order is as follows:

0.10 M CH3COOH < 0.0010 M HCl < 0.10 M HCl.

It is because CH3COOH is a weak acid while HCl is a strong acid. CH3COOH will not ionize all and give out H+ ions for the reaction. Some CH3COOH will still be molecules and in the solution.

HCl is a strong acid, it will fully ionize in water and give out H+ ions. So, the reaction rate will be higher.

ii. The 2 factors are:

The strength of the acid.

The concentration of the acid.

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