Chemistry

Question 1

State the percentage of the gases- nitrogen, oxygen, argon and other gases, in air

Answer 1

78%
21%
0.9%
0.1%

Question 2

State the reactions taking place in a catalytic converter.

Answer 2

2CO + O2 –> 2C02
2NO + 2CO –> N2 + O2
2NO –> N2 + 02

Question 3

What are the 3 states of matter?

Answer 3

Solid
Liquid
Gas

Question 4

What is a volatile liquid?

Answer 4

A liquid which evaporates easily and has a relatively low boiling point

Question 5

What does impurity do to a substance?

Answer 5

• Lowers the melting point
• increases the boiling
  point

Question 6

What does the word miscible mean?

Answer 6

The solvents make a solution

Question 7

How to calculate Rf value in chromatography?

Answer 7

Distance moved by the substance/distance moved by the solvent front

Question 8

What are isotopes?

Answer 8

Atoms of the same element which have the same proton number but a different nucleon number

Question 9

What are radioisotopes?

Answer 9

Isotopes which emit a certain type of radiation.

Question 10

What metals are the most reactive metals that occur?

Answer 10

Alkali metals

Question 11

What are exothermic and endothermic reactions?

Answer 11

Reactions which give-off energy (exothermic)
Reactions with take-in energy (endothermic)

Question 12

What is the law of conservation of mass?

Answer 12

The total mass of all products of a chemical reaction is equal to the total mass of all reactants.

Question 13

Briefly explain the following chemical reactions:
- synthesis
- decomposition
- neutralisation
- precipitation
- displacement

Answer 13

• where two/more reactant form a single product
• where one reactant forms many products
• where an acid and an alkali react to form salt
• where an insoluble solid is formed
• where a more reactive element will displace the less reactive one

Question 14

What are oxidising and reducing agents?

Answer 14

A substance that will add oxygen to a substance (oxidising)
A substance that will remove oxygen from a substance (reducing)

Question 15

Fill in the blanks:
____ is the loss of electrons
____ is the gain of electrons

Answer 15

Oxidation
Reduction

Question 16

What is electrolysis?

Answer 16

The breakdown of an ionic compound, molten or in aqueous solution, by the use of electricity

Question 17

State whether the following are positive or negative:
Cation
Anion
Cathode
Anode

Answer 17

Positive
Negative
Negative
Positive

Question 18

What does the following do to a litmus paper:
Acid
Base

Answer 18

Turns it red
Turns it blue

Question 19

Fill in the blanks:
Non-metals generally form ____ that dissolve in water to form ____ solutions
Metals generally form ____ that dissolves in water to form ____ solutions

Answer 19

Acidic oxides, acidic
Alkaline oxides, basic

Question 20

What is amphoteric hydroxide?

Answer 20

A hydroxide that reacts with both an acid and an alkali to give salt and water

Question 21

What is the test for ammonium salts?

Answer 21

They react with alkali solutions to produce ammonia gas.

Question 22

State the Avogadro constant.

Answer 22

6.02 x 10^23

Question 23

What is the formula to calculate molar-mass?

Answer 23

Mass/no.of moles

Question 24

What is the formula to calculate molar-volume?

Answer 24

Volume/no.of moles

Question 25

What is the molar volume of any gas?

Answer 25

24dm^3

Question 26

What is the formula to calculate concentration?

Answer 26

Amount of solute/volume of solution

Question 27

What is the formula to calculate no.of moles in a solution?

Answer 27

(Concentration/1000) x volume of solution in cm^3

Question 28

Fill in the blanks:
a) Breaking chemical bonds is an __________ process.
b) Making chemical bonds is an __________ process.

Answer 28

a) Endothermic
b) Exothermic

Question 29

State five factors that affect the rate of a reaction.

Answer 29

Surface area
Concentration
Temperature
Catalyst
Influence of light (only sometimes)

Question 30

What happens to the temperature of the surroundings in the following:
a) endothermic reaction
b) exothermic reaction

Answer 30

a) decreases; thermal energy is absorbed
b) increases; thermal energy is given-off

Question 31

What is activation energy?

Answer 31

The minimum quantity of energy, the reactant must possess to undergo a specific reaction

Question 32

Fill in the blanks:
a) Each reaction has its own different value of __________
b) When particles collide, they must have a combined energy __________ than the __________ energy, or else, they will not react
c) Chemical reactions occur when particles __________ with each other

Answer 32

a) Activation
b) Greater, activation
c) Collide

Question 33

Give five factors which affect the rate of a reaction.

Answer 33

Surface area (of solid reactants)
Concentration
Temperature
Catalyst
Influence of light (only sometimes)

Question 34

State the catalysts used in the:
a) Haber process
b) Contact process

Answer 34

a) Iron
b) Vanadium oxide

Question 35

State what is meant by:
a) Valency
b) Valence electron

Answer 35

a) The combining capacity of an atom (Na- 1)
b) The electrons in the outermost shell of an atom (Na- 1; 1 electron in the
outermost shell)

Question 36

Fill in the blank:
Zinc displaces copper because zinc is more _________ than copper.

Answer 36

Reactive