Chemistry Paper 6 (Igcse) -Tips

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1) What is the purpose of ice or cold water?
To cool down the gas so that it condenses and turns into a liquid.

2) when the gas collecting tube is upside down, give a property of this gas. It is less dense than air.

3) Why is a pencil used in drawing the origin line in chromatography? If pen was used, it will dissolve giving colours and so, the experiment won't be accurate. Pencil doesn’t interfere with the results.

4) When using ethanol, give a better apparatus arrangement, and why? Cover apparatus wth a lid, because ethanol is volatile.

5) In the tests and observation tables, when in the first row, they tell you that upon heating condensation occured, there will be a question asking what does this show about the solid? It is hydrated.

6) When copper is used in the test, and the answer is four marks, the best answer is: light blue precipitate (ppt) which is soluble in excess to form dark blue solution.

7) Why is the experiment done in a fume cupboard?
It releases harmful gases that are poisonous. It is toxic.

8) Which result appears to be inaccurate?
It is the point not appearing on the drawn graph, you read it's x-axis and write it with a reason indicating that it doesn't occur in the graph.

9) Why should the solid be crushed?
It increases surface area for a faster rate of reaction.

10) Why is the experiment made in a well-ventilated room?
To prevent burning of the substance.

11) explain the term (decant).
Filter/Pour the liquid leaving the solid alone.

12) Why is concentrated sulphuric acid not used to dry ammonia? Because it will reach the base ammonia, which is neutralization reaction.

13) Why should samples be taken from different parts of the field? To get more accurate results.

14) Suggest why it is important to know the pH of the soil. To see which is the best place for growing, and wht kind of base to use for neutralizing it.

15) What is necessary for rusting?
Water (humidity) and oxygen (air).

16) Suggest why in an experiment for rusting the water level increases. Oxygen is used up, and water is used to take its place.

17) For electrolysis, state the observations.
The bulb will light - A metal is formed on the cathode - Fizz of gases produced.

18) Suggest a suitable material for electrodes.
Graphite - Carbon - Steel.

19) when copper oxide is reacted with hydrogen, what is the colour change? Black to brown, because copper oxide is reduced to copper.
20) How can you distinguish between water and ethanol?
Use cobalt chloride paper, it turns from pink to blue with water, but there will be no change with ethanol. 21) how can you distinguish between sulpharic acid and aqueous sodium sulphate? There are three tests, you can use a metal carbonate in which carbon dioxide will be produced with sulpharic acid but there'd will be no change with sodium sulphate. You can add a metal, in which hydrogen is produced with sulpharic acid, but no change in sodium sulphate. Finally, you could use an indicator like litmus paper, it will change to red with sulpharic acid, but there will be no change with sodium sulphate.. 22) how can you distinguish between hydrochloric acid and nitric acid? Add silver nitrate, in which white ppt will be formed with hydrochloric acid, but there will be no reaction with nitric acid. 23) What is the purpose of the mineral wool?

To absorb and hold the liquid.
24) When there is a delivery tube involved in a question, what precaution should be taken in the experiment when the heat is removed? Remove the delivery tube from water to prevent suck-back.
25) In rate of reactions, always include the word "collisions between particles". 26) How can you distinguish between alkanes and alkane? Use bromine water, in which the alkene will decolourise it to colorless, but nothing happens with an alkane, 27) how can you distinguish between chlorine and sodium chloride? Add litmus paper, it will bleach with chlorine, but nothing...
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