C1.3 Air and Combustion – LearnITbyTests

Question 1 of 34

1. What is the theoretical percentage of nitrogen in the air?

78.1 %

20.90%

0.03%

None

Question 1 of 34

Question 2 of 34

2. Is there a change in mass when a substance burns in air? e.g. magnesium burning with oxygen to give magnesium oxide

Yes, the mass of the product is more than the original mass of magnesium

If the product is solid there is an increase in mass for this case it is solid Magnesium oxide.

If the product could have been gaseous, there could be a decrease in mass

All the above

Question 2 of 34

Question 3 of 34

3. Why is sodium hydroxide preferred to water in the burning candle experiment?

It is cheaper

It is readily available

It easily absorbs carbon (IV) oxide initially in the gas jar and that which is produced during combustion

It is used for cooling.

Question 3 of 34

Question 4 of 34

4. Mention the causes of experimental error in the burning candle experiment which makes its result not the same as the theoretical value of the percentage of oxygen in the air.

Sodium hydroxide solution may not absorb all the carbon (IV) oxide gas

The candle may go off before all the oxygen is used up due to buildup of C02

Poor quality of the candle

Both A and B

Question 4 of 34

Question 5 of 34

5. Substances that absorb moisture from the air to form a solution are called?

Sublimates

Deliquescent

Anhydrous

Hydrated

Question 5 of 34

Question 6 of 34

6. Mention the part of air that supports combustion.

Oxygen

Nitrogen

Carbon (IV) oxide

None of the above

Question 6 of 34

Question 7 of 34

7. A substance such as Manganese (IV) oxide that alters the rate of the chemical reaction is known as:

Reactor

Booster

Catalyst

None

Question 7 of 34

Question 8 of 34

8. Which of the following is not a deliquescent substance?

Anhydrous substance

Magnesium chloride

Zinc chloride

All of the above

Question 8 of 34

Question 9 of 34

9. Define Rusting

Corrosion of steel due to its reaction to acids

Corrosion of iron due to its reaction with atmospheric oxygen

Corrosion of iron due to its reaction with atmospheric oxygen and moisture

None

Question 9 of 34

Question 10 of 34

10. The presence of water and oxygen are necessary for iron to rust. True or False

True

FALSE

Maybe

None

Question 10 of 34

Question 11 of 34

11. What is the theoretical percentage of carbon (IV) oxide in the air?

78.10%

20.90%

0.03%

None

Question 11 of 34

Question 12 of 34

12. When a metal oxide loses oxygen it is said to have been

Minimized

Oxidized

Reduced

None of the above

Question 12 of 34

Question 13 of 34

13. Mention the application of reduction and oxidation

The extraction of metals from their ores uses the concept of reduction

Carbon has the ability to reduce metal oxides in the extraction of copper and zinc from their ore

Both A and B

In separating crude oil.

Question 13 of 34

Question 14 of 34

14. Name the method used to prevent rusting where a more reactive metal such as Zinc or Magnesium is attached to the iron structure so that the more reactive metal can corrode instead of iron.

Alloying

Coating

Sacrificial protection

None

Question 14 of 34

Question 15 of 34

15. How do elements compete for combined Oxygen? E.g. how comes Magnesium removes combined oxygen in Copper (II) oxide to form Magnesium Oxide. Mg + CuO= MgO + Cu.

A more reactive metal removes combined oxygen from a metal oxide of a less reactive metal

More reactive metals displace less reactive metals from their oxides.

More reactive metals are bullies

Both A and B

Question 15 of 34

Question 16 of 34

16. When you heat copper in the presence of air it turns from what color to which one

Red-brown to blue

Red-brown to black

Red-brown to green

None

Question 16 of 34

Question 17 of 34

17. What is the theoretical percentage of oxygen in the atmosphere?

78.10%

20.9 %

0.03%

None

Question 17 of 34

Question 18 of 34

18. When a metal gains oxygen from another metal oxide it is said to have been

Minimized

Oxidized

Reduced

None of the above

Question 18 of 34

Question 19 of 34

19. Removal of oxygen from a substance is called?

Reaction

Reduction

Oxidation

None of the above

Question 19 of 34

Question 20 of 34

20. Air is a mixture of gases such as oxygen, nitrogen, and carbon (IV) oxide and water vapor. True or False

TRUE

FALSE

Maybe

None of the mentioned

Question 20 of 34

Question 21 of 34

21. Which of the following statement about burning a candle in an enclosed gas jar to determine the proportion of air that supports combustion is TRUE?

The candle burns for a while and then it goes off as it uses up the active part of the air in the fixed amount of air enclosed in the gas jar

Greater atmospheric pressure acting on the surface of sodium hydroxide forces the solution to rise in the gas jar and drops outside the jar

The part of air remaining in the gas jar doesn’t support combustion which is 79.1 % and the gas which was used up in oxygen 20.1% which supports combustion

All of the above

Question 21 of 34

Question 22 of 34

22. When most reactive metals such as Potassium, Sodium, Calcium, and Manganese burn in oxygen they form Metal oxides i.e. Sodium + Oxygen = Sodium oxide True or False

FALSE

True

Maybe

None

Question 22 of 34

Question 23 of 34

23. Mention THE USES of oxygen

Air enriched with oxygen is used in hospitals by patients with breathing difficulties

Oxygen is used to burn fuels such as those used for propelling rockets

During steelmaking, oxygen is used to remove iron impurities

All the above are true

Question 23 of 34

Question 24 of 34

24. What is the difference when a substance burns in air and when it burns-in Oxygen?

They burn slower in air

They burn much faster in oxygen

No difference at all

Both A and B

Question 24 of 34

Question 25 of 34

25. The reaction in which elements combine with oxygen is referred to as:

Reaction

Reduction

Oxidation

None of the mentioned

Question 25 of 34

Question 26 of 34

26. Mention the method of preventing rusting

Painting e.g cars, roofs and marine vessel

Coating with other metals through galvanization or electroplating

Alloying – mixing of iron with one or more metals

None

Question 26 of 34

Question 27 of 34

27. Which part of the air slows down the rate of burning?

Oxygen

Carbon (IV) oxide

Nitrogen

Noble Gas

Question 27 of 34

Question 28 of 34

28. What happens when non-metallic elements such as Sulphur, Carbon and Phosphorous burn-in Oxygen? They form Oxides

{Sulphur(IV) oxide, Carbon (IV) oxide, and Phosphorous (V) Oxide}

They form oxides which dissolve in water to form acidic solutions known as Oxides.

Some non-metallic elements form oxides which are not acidic nor basic, neutral oxides

All the above

Question 28 of 34

Question 29 of 34

29. Mention the gases produced during the fractional distillation of liquefied air.

Nitrogen

Oxygen

Noble gas (argon)

All of the above

Question 29 of 34

Question 30 of 34

30. Name the 2 common methods of preparing oxygen in the laboratory.

Heating water molecules to form hydrogen and oxygen gas

Adding water to solid sodium peroxide { SODIUM PEROXIDE + WATER = SODIUM HYDROXIDE + OXYGEN

Heating Potassium Manganite (VII) { Potassium Manganite (VII) = Potassium Manganite (VII) + Manganese (IV) oxide + Oxygen

Both B and C

Question 30 of 34

Question 31 of 34

31. When most reactive metals such as Potassium, Sodium, Calcium, and Manganese burn with Nitrogen they form Metal Nitrides i.e. Sodium + Nitrogen = Sodium Nitride True or False

FALSE

TRUE

Maybe

None

Question 31 of 34

Question 32 of 34

32. Explain the reason behind why gaseous substance when they burn in oxygen, their product has a decrease in mass i.e. carbon + oxygen + carbon (IV) oxide

The product being gaseous it escapes into the air

The product being gaseous has negligible mass

No proper weighing balance to weigh the gaseous product

None of the above

Question 32 of 34

Question 33 of 34

33. Mention the experiment used to determine the proportion of air that supports combustion.

When a candle is burned in an enclosed gas jar in a trough of sodium hydroxide

Heating copper in a fixed volume of air

Smoldering of phosphorus in an enclosed measuring cylinder in a trough of water

All of the above

Question 33 of 34

Question 34 of 34

34. Mention the possible sources of error in heating copper in a fixed volume of air experiment.

The air initially present in the tube is not accounted for

There is a possible leakage of air

Not all oxygen is used up

All of the above

Question 34 of 34

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