Chemistry - Ans.fyi 參考答案

Chemistry

用戶231342

2010-07-05 1:56 am

1.When a flame test is performed on copper(II) chloride, what is the colour of the flame observed?
2.For each of the following pairs of elements, suggest 1 reaction in which both element s behave similarly. In each case, write a chemical equation for the reaction involving either one of the elements.
(i) magnesium and calcium (ii) chlorine and bromine
3.Xenon (Xe) is a group 0 element. State, with explanation, what will happen if a ballon filled with xenon is release from the top of a tower.
4.Six compounds are classified into 2 groups as shown in the table below:
Gas: Ammonia, Carbon dioxide, Nitrogen dioxide
Solid: Iron(III) oxide Magnesium oxide, potassium oxide
Reclassify these compounds into 2 groups, according to
(a) one of their physical properties
(b) one of their chemical properties
5.32 g of sodium chloride, 32 g of tetrachloromethane and 50 cm3 of water are shaken together in a stoppered bottle and then allowed to settle, after a few mins, what would be observed?
6.Aluminium and Iron can be used in making window frames. Discrible an experiment to show that aluminium is more reactive than iron.

回答 (1)

andrew

2010-07-05 5:31 am

✔ 最佳答案

1.
A bluish green flame is observed.

2.
(i)
Both magnesium and calcium react with dilute hydrochloric acid to give hydrogen gas.
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Ca(s) + 2HCl(aq) → CaCl2(aq) + H2(g)

(ii)
Both chlorine and bromine react with potassium iodide solution to give iodine.
Cl2(g/aq) + 2KI(aq) → 2KCl(aq) + I2(aq)
Br2(g/aq) + 2KI(aq) → 2KBr(aq) + I2(aq)

3.
The balloon falls to the ground.
The relative atomic mass of xenon is 131.3, which is much higher than the average relative molecular mass of air. The balloon falls to the ground because the density of xenon and that of the plastic to make the balloon are higher than that of water.

4.
(a)
White/colourless: ammonia, carbon dioxide, magnesium oxide, potassium oxide
Coloured: nitrogen dioxide, iron(III) ox ide

(b)
Acidic (reacting with dilute alkali): carbon dioxide, nitrogen dioxide
Basic (reacting with dilute acid): ammonia, iron(III) oxide, magnesium oxide, potassium oxide

5.
There are two layers of liquid. The top layer is the aqueous layer, and the bottom layer is the tetrachloromethane layer.
A half of the sodium chloride dissolves (in water). The undissolved sodium chloride sinks to the bottom.

6.
Burn separately aluminium powder and iron powder in oxygen.
Aluminium powder burns more brightly, while iron powder only glows.

參考: andrew

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