Chemistry question

TommyWONG

2011-03-05 6:25 am

1. A student investigated the action of heat on calcium carbonate by the following steps:
step1 heat some calcium carbonate on the liquid into a boiling tube
step2 add a few drops of water to the solid product formed in step1
step3 put the substance obtained into a small beaker. Half fill the beaker with water and stir the mixture
step4 filter about 10cm3 of the reation occurred in step2
step5 blow through a straw into the liquid in the boiling tube

a) Draw a labelled diagram of the experimental sep-up used in step 4

3. For each of the following pairs of samples, suggest a test to distinguish between them. State your expected observations in each case.

a) Dilute hydrochloric acid and dilute nitric acid
b) Iron(II) sulphate and iron(III) sulphate
c) solid ammonium chloride and solid magnesium chloride

回答 (1)

pingshek

2011-03-05 11:03 am

✔ 最佳答案

1. (a)
http://library.thinkquest.org/11430/research/images/filtration.gif

圖片參考：http://library.thinkquest.org/11430/research/images/filtration.gif

= = = = =
3.(a)
Add separately some copper turnings to each of the two solutions.
Dilute hydrochloric acid: There is no observable change.
Dilute nitric acid: A colourless gas (nitrogen monoxide) is formed which turns brown (nitrogen dioxide) when mixed with the air.

3(b)
If the samples are solid, dissolve separately the two samples in water to form two solutions. Then add separately some drops of sodium hydroxide to each of the solutions.
Iron(II) sulphate: A pale green precipitate (iron(II) hydroxide) is formed.
Iron(III) sulphate: A brown precipitate (iron(III) hydroxide) is formed.

3(c)
Dissolve separately the two solid sample in distilled water to form two solutions. Then, add separately some sodium carbonate solution to each of the two solutions.
Solid ammonium chloride: When heated, a pungent gas (NH3) is formed which turns moist red litmus paper blue.
Solid magnesium chloride: A white precipitate (MgCO3) is formed.

參考: miraco

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