Gases in the atmosphere

Question 1

What are the 4 most abundant gases in dry air? - Give the formula of the Gases.

Answer 1

N₂, O₂, Ar, CO₂

Question 2

What is the percentage composition of oxygen gas in the air?

Answer 2

21%

Question 3

What is the percentage composition of carbon gas dioxide in the air?

Answer 3

0.04%

Question 4

What is the percentage composition of nitrogen gas in the air?

Answer 4

78%

Question 5

What is the percentage composition of argon gas in the air?

Answer 5

0.9%

Question 6

What temperature does water freeze at?

Answer 6

0ºC

Question 7

What temperature does water boil at?

Answer 7

100ºC

Question 8

What is thermal decomposition?

Answer 8

Thermal decomposition is the breakdown of substances into two or more substances using heat.

Question 9

What is the general equation for the thermal decomposition of metal carbonates?

Answer 9

metal carbonate → metal oxide + carbon dioxide

Question 9

What does the formation of black copper(II) oxide indicate? - Measuring oxygen using copper

Answer 9

It indicates that the oxygen from the air has reacted with copper.

Question 9

What is the purpose of the experiment? - Measuring oxygen using iron

Answer 9

The purpose is to determine the percentage by volume of oxygen in air using iron.

Question 9

What is a hydrocarbon?

Answer 9

A hydrocarbon is a compound containing hydrogen and carbon atoms only.

Question 9

What apparatus is needed in this experiment? - Measuring oxygen using copper

Answer 9

The apparatus consists of two syringes connected to a copper sample. Air is passed over the copper while it is heated.

Question 9

What is a Fuel?

Answer 9

A fuel is a substance that, when burned, releases heat energy.

Question 9

What is the method for measuring oxygen using copper? - measuring oxygen using copper

Answer 9

Copper is heated while air is passed over it between the syringes. There must be an excess of copper and all of the oxygen present will react with copper to form black copper(II) oxide. The volume of
gas measured in the syringes will fall by the percentage of oxygen present.

Question 9

What is the chemical equation for the reaction between copper and oxygen? - measuring oxygen using copper

Answer 9

copper + oxygen → copper(II) oxide
2 Cu(s) + O2(g) → 2 CuO(s)

Question 9

What apparatus is used in this experiment? - Measuring oxygen using iron

Answer 9

A eudiometer—a glass tube closed at one end with graduations—is used. The eudiometer is inverted in a beaker of water.

Question 10

What is placed inside the eudiometer? - Measuring oxygen using iron

Answer 10

Damp iron wool or iron filings are placed inside the eudiometer.

Question 11

What happens as the iron reacts with oxygen and water? - Measuring oxygen using iron

Answer 11

The iron reacts with oxygen and water to form hydrated iron(III) oxide (rust), consuming all the oxygen in the air.

Question 12

How is the percentage of oxygen determined? - Measuring oxygen using iron

Answer 12

The level of water in the eudiometer rises as the iron reacts, indicating the volume of oxygen that reacted and allowing for the determination of the percentage of oxygen in the air sample.

Question 13

What is the balanced chemical equation for the reaction? - Measuring oxygen using iron

Answer 13

iron + water + oxygen → hydrated iron(III) oxide

Question 14

What other equipment is used in the experiment? - Measuring oxygen using iron

Answer 14

The experiment may involve a gas syringe, heat source, and rubber bung to seal the eudiometer.

Question 15

What is the purpose of using damp iron in the experiment? - Measuring oxygen using iron

Answer 15

Damp iron enhances the reaction with oxygen and water, ensuring that all the oxygen in the air is consumed.

Question 16

How can the presence of oxygen be tested?

Answer 16

Insert a glowing splint into the sample. If the splint relights, it indicates the presence of oxygen.

Question 17

What happens when magnesium reacts with oxygen?

Answer 17

Magnesium burns with a bright white light, forming a white solid called magnesium oxide. magnesium + oxygen → magnesium oxide 2 Mg(s) + O2(g) → 2 MgO(s)

Question 18

How does sulfur react with oxygen?

Answer 18

Sulphur burns with a blue flame, producing sulphur dioxide gas. sulphur + oxygen → sulphur dioxide S(s) + O2(g) → SO2(g)

Question 19

What are the products of complete combustion of hydrocarbons?

Answer 19

The products of complete combustion are carbon dioxide and water. hydrocarbon + oxygen → carbon dioxide + water

Question 20

How does carbon dioxide contribute to global warming?

Answer 20

Carbon dioxide is a greenhouse gas that traps infrared radiation within our atmosphere, contributing to global warming.

Question 21

What is incomplete combustion of a hydrocarbon?

Answer 21

Incomplete combustion of a hydrocarbon occurs in a limited supply of oxygen.

Question 22

What are the products of incomplete combustion?

Answer 22

The products of incomplete combustion are carbon (soot) or carbon monoxide, as well as water.

Question 23

What are the characteristics and effects of carbon monoxide?

Answer 23

Carbon monoxide is a poisonous, odourless gas. It binds very strongly to haemoglobin in the blood, limiting the oxygen carrying capacity of blood. This makes carbon monoxide toxic.

Question 24

How are nitrogen oxides formed in car engines?

Answer 24

Nitrogen oxides are formed in car engines when oxygen reacts with nitrogen at high temperatures.

Question 25

How is sulphur dioxide produced during fuel combustion?

Answer 25

Sulphur dioxide is produced when hydrocarbon fuels containing sulphur are burned.

Question 26

How do nitrogen oxides and sulphur dioxide contribute to acid rain?

Answer 26

Nitrogen oxides and sulphur dioxide are nonmetal oxides that dissolve in rainwater, contributing to the formation of acid rain.

Question 27

How can the presence of water be tested using anhydrous copper(II) sulphate?

Answer 27

Adding a liquid to white anhydrous copper(II) sulphate will cause it to turn blue and form hydrated copper(II) sulphate if water is present.