Exam Questions

Question 1

Define the term isotomic mass

Answer 1

The mass of an atom compared to 1/12th of C12

Question 2

What does ‘.xH2O’ represent?

Answer 2

Water of crystalisation

Question 3

Define the term atomic mass

Answer 3

It is the mean mass of an atom compared to 1/12th of carbon 12

Question 4

Define the term ionic bonding

Answer 4

The electrostatci attraction between oppositely charaged ions

Question 5

What is ment by the term isotopes?

Answer 5

Atoms of an element with different numbers of neutrons

Question 6

Different isotopes of antimony have the same chemical propertu. Explain why.

Answer 6

They have the same number of electrons in their outmost shell

Question 7

Define the term relative atomic mass

Answer 7

It is the mean mass of an atom compaired to 1/12th of carbon 12

Question 8

What is meant by an orbital?

Answer 8

A region that can hold two electrons

Question 9

State the total number of electrons occupying the p orbitals in one chlorine atom

Answer 9

11

Question 10

Explain why xenon has a lower firs ionisation energy than neon

Answer 10

Xeon has more shells and more shielding. The nucleus attraction decreases

Question 11

Explain why xenon has a lower first ionisation energy than neon

Answer 11

Xeon has more shells and more shielding. The nucleus attraction decreases

Question 12

What is the relative mass of an electron?

Answer 12

1/1836

Question 13

Define the term relative isotopic mass

Answer 13

The mass of an atom compared to 1/12th of C12

Question 14

What is meant by one mole of a substance?

Answer 14

The amount of substance which contains as many particles as there are carbon atoms in 12g of carbon-12

Question 15

Predict the shape and bond angle of lead in lead tetraethyl, explain your answer.

Answer 15

Shape: Tetrahedral
Bond angle: 109o
Explanation: It has four sets of electrons, which repel as far from each other as possible

Question 16

Why is Na3PO4 described as a salt of H3PO4?

Answer 16

The H+ ions are replaced by sodium ions

Question 17

What are the main intermolecular forces in NH3?

Answer 17

Hydrogen bonding

Question 18

What are the main intermolecular forces in PH3?

Answer 18

Permanent dipole

Question 19

What is a dative covalent bond?

Answer 19

Both electrons have been dnated by 1 atom

Question 20

What is the bond angle of F-B-F in BF3?

Answer 20

120o

Question 21

What is the bond angle of F-B-F in H3NBF3?

Answer 21

109.5o

Question 22

The H-N-H bond angle in NH3 is 107o. A student predicted the the H-N-H bond angle in H3NBF is larger.
Explain why the student may have expected the H-N-H bond angle to be larger in H3NBF3 than in NH3

Answer 22

N in NH3 has 3 bonding pairs and 1 lone pair of electrons
N in H3NBF3 has 4 bonding pairs of electrons
Lone pair of electrons repel more than bonding pairs

Question 23

State the shape of a molecule of SF6

Answer 23

Octahedral

Question 24

Molecules of BF3 contain polar bonds, but the molecules are non-polar, why?

Answer 24

BF3 is symmetrical and therefore the dipoles cancel out

Question 25

What si the shape of a molecule of SbCl3 and why?

Answer 25

Shape: Trigonal pyramid
Explanation: Sb has 3 bonding prais and 1 lone pair of electrons. Pairs of electrons repel

Question 26

Why is SbCl3 polar?

Answer 26

There is difference of electronegativity and the dipoles don’t cancel out

Question 27

What are the formulae of the ions present in the salt, H4N2O3?

Answer 27

NH4+ and NO3-

Question 28

State 2 examples of anomalous properties of ice caused by Hydrogen bonding

Answer 28

Ice is less dense than water - molecules of ice are held by H-bonds
Ice has a relatively high melting point - H-bonds relatively strong

Question 29

Explain why lithium fluoride conducts electricity when molten but not when solid

Answer 29

Ions cannot move in solids but they can when in molten

Question 30

Fluorine reacts with boron, B, to form the fluoride BF3. Suggest an equation for this reaction

Answer 30

2B + 3F2 —> 2BF3

Question 31

Name the shape of, and state the bond angles in, a BF3 molecule. Explain why BF3 has this shape

Answer 31

Shape: Trigonal planar
Angle: 120o
Explanation: The pairs of electrons repel. Boron has 3 bonded pairs

Question 32

Explain why NF3 has a permanent dipole

Answer 32

F is more electronegative than N

Dipoles don’t cancel

Question 33

In terms of protons, neutrons and electrons, how is an atom of 151Eu different from an atom of 153Eu?

Answer 33

153 has to more neutrons

Question 34

In terms of protons, neutrons and electrons, how is an atom of 151Eu similar from an atom of 153Eu?

Answer 34

Same number of protons and electrons

Question 35

Why is calcium nitrate an example of a salt?

Answer 35

The H+ ions in a nitric acid has been replaced by calcium ions

Question 36

Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid

Answer 36

Accepts a proton

Question 37

Predict the bond angle in an F2O molecule, explain your anser

Answer 37

BOnd angle: 104 -105

Explanation: There are 2 bonded pairs and 2 lone paira. The lone apris repal more than the bonded pairs

Question 38

What term is used to describe a redox reaction in which an element is both oxidised and reduced?

Answer 38

Disproportional

Question 39

Name the shape of a molecule of CH3Cl

Answer 39

Tetrahedral

Question 40

Explain why ZnCl2 is a salt

Answer 40

H+ ions are replaced by zinc ions

Question 41

What is meant by the term hydrated calcium chloride?

Answer 41

Contains water of crystallisation

Question 42

How many full orbitals are an atom of sulfur?

Answer 42

7

Question 43

Why can ammonium be described as a salt?

Answer 43

The H+ ions have been replaced by ammonium ion