EL From Sep 2015

Question 1

What is atomic Number?

Answer 1

This is the number of protons in an atom.

It is also the number of electrons in that atom.

Question 2

What is atomic mass?

Answer 2

This is the number of protons and neutrons in an atom combined.

Question 3

What is ionisation energy?

Answer 3

This is the energy to remove 1 mole of electrons from 1 mole of gaeous atoms (ie, 1 electron per atom) to form 1 mole of gaseous cations:

X_(g) –> X⁺_(g) + e^-

Question 4

What is a cation?

Answer 4

A positively charged ion

Question 5

What is an anion?

Answer 5

A negatively charged ion

Question 6

Describe the simple model of the atom

Answer 6

Protons and Neutrons in the nucleus, surrounded by an electron cloud. (image to follow)

Question 7

What are the maximum number of electrons that can be found in each shell?

Answer 7

S sub shell –> 2

P sub shell –> 6

D sub shell –> 10

F sub shell –> 14

Question 8

Subtract the molecular mass of ammonia from the molecular mass of ammonium

Answer 8

NH₄ - NH₃ = 1

18-17=1

Question 9

What is the difference between Ar and Mr?

Answer 9

• Ar* is the relative atomic mass
• Mr* is the relative molecular mass

Question 10

How is the relative atomic mass of each element relatd to carbon-12?

Answer 10

The average atomic mass of each element is ¹/₁₂ of the mass of carbon-12

Question 11

What is Avogadro’s constant?

Answer 11

6.02 x 10²³

A mole!

Question 12

What happens when hydrated crystals are heated?

Answer 12

The water of crystallisation is removed as steam

An anhydrous solid is produced

Question 13

What factors reduce the theoretical amount of product that should be produced?

Answer 13

• Loss of product
• Impurities in reactants
• Changes in temperature
• Changes in pressure
• Which way the equilibbrium lies

Question 14

Balance the following equation

KNO₃ + C₁₂H₂₂O₁₁ –> N₂ + CO₂ + H₂O + K₂CO₃
Good luck.

Answer 14

48KNO₃ + 5C₁₂H₂₂O₁₁ –> 24N₂ + 36CO₂ + 55H₂O + 24K₂CO₃

Question 15

How do the reactivities of Group 1 and Group 2 elements change?

Answer 15

As you go down the group:

The reactivity increases because there are more shells shielding the positive nucleus, so it is easier for the negative electrons to move away.

As you go across the period:

The reactivity decreases because more positive protons are added to the nucleus, so the electrons are more strongly attracted.

Question 16

How do the first ionisation enthalpies change across a period?

Answer 16

The first ionisation enthalpies of elements increase as you go across a period because there are more protons in the nucleus, so the electrons are held tighter.

Question 17

How do successive ionisation enthalpies change?

Answer 17

As more electrons are removed, the ionisation enthalpy increases because they are held more tightly to the nucleus, so it takes more energy to pull them away.

Question 18

How do Group 2 elements react with oxygen and water?

Answer 18

Oxygen - produces metal oxide (‘M’ means any group 2 element)

2M_(s) + O_2(g) > 2MO_(s)

Water - form hydroxides and hydrogen

M_(s) + 2H₂O_(l) > M(OH)_2(aq) + H_2(g)

The further down the element in the group, the faster the reaction.

Question 19

Explain Valence Shell Electron Repulsion theory

Answer 19

Electrons in the valence shell are all negatively charged so repel each other; this means that when they form bonds they will station themselves as far away from other bonding pairs or nonbonding pairs as possible.

Question 20

What is the significance of a loan pair of valence electrons in a compound?

Answer 20

The lone pair repels with greater force than a bonding pair.

Question 21

​What type of bond does and arrow represent and define the term?

Answer 21

Dative covalent bond:

This means that one atom donates both electrons that make up the covalent bonding pair.

Question 22

What is shape and bond angle if a molecule has 3 bonding pairs around the central atom and one lone pair?

Answer 22

Pyramidal, 107.3 degrees

Question 23

What is the shape of a molecule and bond angle if it has 5 bonding pairs around the central atom?

Answer 23

Bipyramidal 90 degrees and 120 degrees

Question 24

The

Question 25

The velocity of light in a vaccum can be approximated to be 3E08m/s. The wavelength of red light is 656nm, therefore what is the energy of a wave of red light?

The plancks constant is 6.63E-34Js

Answer 25

Speed of light=Frequency*Wavelength

656nm=656E-09m

3E08/656E-09=4.57E14

Frequency=4.57E14

Energy=Planck’s constant*Frequency

6.63E-34*4.57E14=3.03E-19J

Energy= 3.03E-19J

Question 26

What made the proposition of electrons orbiting at discrete energy levels controversial?

Answer 26

It was based on the theory of quantisation of energy.

Question 27

For a flame test of Lithium, Sodium, Potassium, Calcium, Barium, and Copper, what should the experimental results be?

Answer 27

Lithium=Bright red

Sodium=Yellow

Potassium=Lilac

Calcium:Brick red

Barium=Apple green

Copper=Blue green

Question 28

What is wave-particle duality?

Answer 28

Light can behave both as waves and particles.

Question 29

With respect to energy levels what does “n” represent?

Answer 29

The quantum number (also known as the energy level which corresponds to shells).

Question 30

What causes the lymann series and what part of the electromagnetic spectrum is prdouced?

Answer 30

Electronic transition from a higher energy level to the first energy level to produce UV.

Question 31

What causes the Balmer series and what part of the electromagnetic spectrum is produced?

Answer 31

Electronic transition from a higher energy level to the second energy level producing visible light.

Question 34

What are the three types of nuclear radiation?

Answer 34

Alpha - particles = ⁴₂ A - two protons two neutrons

Beta - particles = ⁰ ₁ ß - an electron

Gamma - radiation = only emitted after either an alpha or a beta particle

Question 35

What are the two units for frequency?

Answer 35

Hz

S^-1

Question 36

Name the flame colours for the following ions

Li⁺
Na⁺
K⁺
Ba²⁺
Ca²⁺
Cu²⁺

Answer 36

Li+ —— Bright red
Na+ —— Yellow
K+ —— Lilac
Ba2+ —— Brick red
Ca2+ ——Apple green
Cu2+ ——Blue green