唔該我Chem 高手請進.... thanks....

candy

2009-07-24 6:03 pm

1.The mass of a sample of copper powder contaminated with CuO is known. Describe how you would conduct an experiment to determine the percentage by mass of copper powder in the sample. State the expected observation of the experiment.
( Hint: you may use an acid in the experiment)

可唔可以講解下點樣做這題,步驟...
thanks

回答 (1)

六呎將軍

2009-07-24 7:11 pm

✔ 最佳答案

Steps are as follows:
1. Weigh the raw sample with an electronic balance and record down its mass, say m1.
2. Put the sample in dilute hydrochloric acid and the acid turns blue in colour as a result of dissoving copper(II) oxide, which is a base, in the acid. Stir the mixture well until no further dissolving occurs.
3. The residue left will be the copper metal since dilute hydrochloric acid cannot dissolve copper.
4. Filter the residue, followed by rinsing with distilled water and dried up.
5. Weigh the dried residue with an electronic balance and record down its mass, say m2.
6. Percentage by mass of copper powder in the sample = (m2/m1) x 100%

參考: Myself

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