Module 2 - Foundations in Chemistry - Exam Questions

Question 1

Define relative isotopic mass (2)

Answer 1

Mass of the isotope compared to 1/12th of the mass of a carbon 12

Question 2

Define isotopes (1)

Answer 2

Atoms with the same number of protons but a different number of neutrons

Question 3

Explain why isotopes have the same chemical properties (1)

Answer 3

Same number of electrons in the outer shell

Question 4

Define relative atomic mass (3)

Answer 4

The weighted mean mass of an atom relative to 1/12th the mass of one atom of carbon 12

Question 5

How could the fraction of the isotopes of carbon be found experimentally? (1)

Answer 5

Mass spectrometry

Question 6

Explain what is meant by a salt (1)

Answer 6

When the H+ in an acid is replaced by a metal ion

Question 7

What term is given to the .n H2O part of a formula? (1)

Answer 7

Waters of crystallisation

Question 8

What calcium compound is formed when calcium oxide reacts with water? (1)

Answer 8

Calcium hydroxide

Question 9

What calcium compound is formed when calcium oxide reacts with nitric acid? (1)

Answer 9

Calcium nitrate

Question 10

How do old samples of magnesium oxide become contaminated with magnesium carbonate? (1)

Answer 10

MgO has reacted with CO2

Question 11

A student adds an excess of HCl to magnesium oxide and magnesium carbonate, state two observations that would be made (2)

Answer 11

Solid dissolves

Effervescence

Question 12

Define an acid (1)

Answer 12

A proton donor

Question 13

How can CaCO3 be used to combat excess stomach acid? Use an equation (2)

Answer 13

CaCO3 neutralises HCl

CaCO3 + 2HCl -> CaCl2 + H2O + CO2

Question 14

State an important use of ammonium sulphate (1)

Answer 14

Fertiliser

Question 15

State a large-scale use of ammonia (1)

Answer 15

Manufacture of explosives

Question 16

Use oxidation numbers to explain why the reaction involves both oxidation and reduction (algebraically) (3)

Answer 16

X: oxidation number goes up
Y: oxidation number goes down
X is oxidised and Y is reduced

Question 17

Explain, in terms of electrons, what is meant by oxidation (1)

Answer 17

Loss of electrons

Question 18

What is meant by the term mole? (1)

Answer 18

Amount of substance that has the same number of particles as there are atoms in 12g of carbon 12

Question 19

What is a common use of NaClO? (1)

Answer 19

Bleach

Question 20

Define empirical formula (1)

Answer 20

Simples whole number ratio of atoms

Question 21

After Ca has fully reacted with HCl, upon adding more Ca, a reaction still takes place, why? (3)

Answer 21

Ca has reacted with water

Ca + 2H2O -> Ca(OH)2 + H2

Question 22

Explain what is meant by molecular formula (1)

Answer 22

Number and type of atoms making up a molecule

Question 23

What is meant by ionic bonding? (1)

Answer 23

Electrostatic attraction between oppositely charged ions

Question 24

Predict the bond angle in an F2O molecule and explain (3)

Answer 24

104.5
There are 2 bonded pairs and 2 lone pairs
Lone pairs repel more than bonded pairs

Question 25

Describe and explain two anomalous properties of water from hydrogen bonding (4)

Answer 25

Liquid H2O is more dense than solid Ice has open lattice H2O has a relatively high boiling point Hydrogen bonds need to be broken

Question 26

Magnesium melting point: 650°C Chlorine melting point: -101°C Describe the structure and bonding of these elements and explain the difference in melting points (6)

Answer 26

Mg has a giant structure Mg has metallic bonding Electrostatic attraction between positive ions and electrons Cl has a simple covalent lattice Cl has induced dipole-dipole Less energy is needed to overcome induced dipole-dipole than metallic bonds

Question 27

Describe the bonding and structure in graphite | Explain why graphite is a good conductor, a soft material and a very high melting point (5)

Answer 27

``` Giant covalent lattice Arranged in layers Good conductor - mobile electrons High melting point - covalent bonds have to be broken Soft - weak forces between the layers ```

Question 28

What is meant by a covalent bond? (1)

Answer 28

A shared pair of electrons

Question 29

Name the shape of the ammonia molecule and why ammonia has this shape and a bond angle of 107° (3)

Answer 29

Pyramidal There are 3 bonded pairs and 1 lone pair Lone pairs repel more than bonded pairs

Question 30

Why does ammonium chloride not conduct electricity when solid but does when dissolved in water? (2)

Answer 30

Ions cannot move in a solid | Ions can move in solution

Question 31

What is meant by metallic bonding? (2)

Answer 31

Electrostatic attraction between the delocalised electrons and the positive ions

Question 32

Why does H2S have a much lower boiling point than H2O? (2)

Answer 32

No hydrogen bonding | Weaker intermolecular forces

Question 33

What is meant by hydrogen bonding? (1)

Answer 33

Interaction between lone pair of F, N or O and a H in a neighbouring molecule

Question 34

Explain electronegativity (2)

Answer 34

Attraction of an atom for electrons in a covalent bond

Question 35

Why do O-H and N-H bonds have dipoles? (1)

Answer 35

Oxygen and nitrogen are more electronegative than hydrogen

Question 36

Why does a water molecule have a different shape to a carbon dioxide molecule? (2)

Answer 36

Electron pairs repel Oxygen in water has 2 bonds and 2 lone pairs Carbon in CO2 has 2 double bonds

Question 37

Why is water a polar molecule, but CO2 is not?

Answer 37

CO2 is symmetrical | In CO2, dipoles cancel