Elements of Life

Question 1

What is Avogadro’s constant?

Answer 1

Avogadro’s constant (Nₐ) is the number of particles in 1 mole of a substance
Nₐ = 6.02x10²³

Question 2

Define Relative atomic mass (Ar)

Answer 2

The number of times an atom of an element is heavier than one-twelfth of an atom of ¹²C

Question 3

Define Relative formula mass (Mr)

Answer 3

The sum of the relative atomic masses for each atom in the formula
For simple molecules it is sometimes called relative molecular mass

Question 4

Define Empirical formula

Answer 4

The simplest ratio of atoms of each element in a compound

Question 5

Define Molecular formula

Answer 5

The actual number of atoms of each element in a compound

may be the same as or a whole number multiple of the empirical formula

Question 6

Give the equation for moles

Answer 6

Mass = Mr x moles
moles = Mass / Mr

Question 7

Define mass number

Answer 7

The number of protons and neutrons in a nucleus

Question 8

Define atomic number

Answer 8

The number of protons in a nucleus

Question 9

Give the relative atomic mass of a:

i) proton
ii) neutron
iii) electron

Answer 9

i) 1
ii) 1
iii) Very small (0.00055)

Question 10

Give the relative charge of a:

i) proton
ii) neutron
iii) electron

Answer 10

i) 1+
ii) 0
iii) 1-

Question 11

Define isotope

Answer 11

Atoms of the same element that have the same atomic number but different mass numbers

Question 12

How would you calculate the relative atomic mass from the relative isotopic masses and abundance

Answer 12

(Isotopic mass x % abundance) + (Isotopic mass x % abundance) / 100

Question 13

What is for α radiation, state:

i) What it is
ii) Its relative charge
iii) How does the parent nucleus change when it is emitted
iv) What can it be stopped by
v) Level of deflection in an electric field

Answer 13

i) Helium nuclei
ii) 2+
iii) 2 fewer protons, 2 fewer neutrons
iv) paper or skin
v) low

Question 14

What is for β radiation, state:

i) What it is
ii) Its relative charge
iii) How does the parent nucleus change when it is emitted
iv) What can it be stopped by
v) Level of deflection in an electric field

Answer 14

i) electrons
ii) 1-
iii) 1 more proton, 1 fewer neutron
iv) aluminium foil
v) high

Question 15

What is for γ radiation, state:

i) What it is
ii) Its relative charge
iii) How does the parent nucleus change when it is emitted
iv) What can it be stopped by
v) Level of deflection in an electric field

Answer 15

i) electromagnetic radiation
ii) 0
iii) no change
iv) lead sheet or thick concrete
v) none

Question 16

Define half-life

Answer 16

The time taken for half of a radioactive nuclei sample to decay

Question 17

Define tracers

Answer 17

Radioactive isotopes whose decay is monitored

Question 18

Define nuclear fusion

Answer 18

The joining together of two or more nuclei to form a heavier nucleus of a new element

Question 19

What conditions are required for nuclear fusion and why

Answer 19

High temperature and/or pressure to provide energy needed to overcome the repulsion between 2 positive nuclei

Question 20

Describe the change in energy levels as the distance from the nucleus increases

Answer 20

The energy levels increase, but the difference in energy levels (ΔE) decreases as the electron moves away from the nucleus

Question 21

Describe an absorption spectrum

Answer 21

Black lines on a coloured background with the black lines corresponding to the frequencies of light absorbed
The lines get closer at higher frequencies

Question 22

Describe an emission spectrum

Answer 22

Coloured lines on a black background with the coloured lines corresponding to the frequencies of light emitted
The lines get closer at higher frequencies

Question 23

State the maximum number of electrons possible in each electron shell:

i) 1st
ii) 2nd
iii) 3rd
iv) 4th

Answer 23

i) 2
ii) 8
iii) 18
iv) 32

electrons in shell = 2n²

Question 24

Give the bonding for the following pairs of atoms:

i) Metal - Metal
ii) Metal - Non-metal
iii) Non-metal - Non-metal

Answer 24

i) Metallic
ii) Ionic
iii) Covalent

Question 25

For an ionic lattice, state: i) an example ii) type of bonding iii) melting point iv) solubility in water v) electrical conductivity

Answer 25

i) NaCl ii) ionic iii) high iv) usually soluble v) only if molten or in solution

Question 26

For a giant covalent network, state: i) an example ii) type of bonding iii) melting point iv) solubility in water v) electrical conductivity

Answer 26

i) SiO₂, Diamond ii) Covalent iii) High iv) insoluble v) no (except graphite)

Question 27

For a simple molecular, state: i) an example ii) type of bonding iii) melting point iv) solubility in water v) electrical conductivity

Answer 27

i) CO₂, H₂O ii) Covalent iii) low iv) usually insoluble v) no

Question 28

For a metallic lattice, state: i) an example ii) type of bonding iii) melting point iv) solubility in water v) electrical conductivity

Answer 28

i) Na, Mg ii) Metallic iii) High iv) insoluble v) yes

Question 29

Describe the structure of ionic bonding and how it is formed

Answer 29

The metal atom transfers electron(s) to the non-metal creating charged ions The cations and anions are held together in a giant ionic lattice by the electrostatic attraction between the charged ions

Question 30

Define covalent bonding

Answer 30

The two non-metals share electrons to achieve a full outer shell

Question 31

Define dative covalent bonding

Answer 31

Where both of the electrons in the covalent bond come from the same atom

Question 32

Define metallic bonding

Answer 32

Positively charged metal ions arranged regularly in a lattice in a 'sea' of delocalised electron

Question 33

Give the shape and bond angle for a central atom surrounded by 4 bonding pairs of electrons

Answer 33

Tetrahedral | 109.5°

Question 34

Give the shape and bond angle for a central atom surrounded by 3 bonding pairs of electrons, and 1 lone pair

Answer 34

Pyramidal | 107°

Question 35

Give the shape and bond angle for a central atom surrounded by 2 bonding pairs and 2 lone pairs of electron

Answer 35

Bent | 104.5°

Question 36

Give the shape and bond angle for a central atom surround by 3 bonding pairs of electrons

Answer 36

Trigonal Planar | 120°

Question 37

Give the shape and bond angle for a central atom surrounded by 5 bonding pairs of electrons

Answer 37

Trigonal bipyramidal | 120° and 90°

Question 38

Give the shape and bond angle for the central atom surrounded by 6 bonding pairs of electrons

Answer 38

Octahedral | 90°

Question 39

Give the shape and bond angle for the central atom surrounded by 2 areas of electron density

Answer 39

Linear | 180°

Question 40

How did Mendeleev arrange the elements in his periodic table?

Answer 40

In order of relative atomic mass

Question 41

When is periodicity exhibited?

Answer 41

When: - there is a regular pattern in a property as you go across a period - the regular pattern is repeated in other periods

Question 42

Give 2 examples of periodicity

Answer 42

Melting points | Boiling points

Question 43

Describe the trend in boiling points across period 2 and 3

Answer 43

``` Period 2: - an increase Lithium - Carbon - a sharp decrease Carbon - Nitrogen - remains low Nitrogen - Neon Period 3: - an increase Sodium - Silicon - a sharp decrease Silicon - Phosphorus - remains low Phosphorus - Argon ```

Question 44

Explain the common rise and fall in boiling point across a period

Answer 44

- Metals have a metallic lattice structures (high boiling points) - Some group 4 elements form covalent network structures (very high boiling point) - Other non-metals have simple molecular structures (low boiling points)

Question 45

Why did Mendeleev leave gaps in his periodic table?

Answer 45

For elements he thought were yet to be discovered

Question 46

Give the formula for Hydroxide ions

Answer 46

OH⁻

Question 47

Give the formula for Oxide ions

Answer 47

O²⁻

Question 48

Give the formula for Carbonate ions

Answer 48

CO₃²⁻

Question 49

Give the formula for Sulfate ions

Answer 49

SO₄²⁻

Question 50

Give the formula for Nitrate (V) ions

Answer 50

NO₃⁻

Question 51

Give the formula for Ammonium ions

Answer 51

NH₄⁺

Question 52

Give the formula for Hydrogen Carbonate ions

Answer 52

HCO₃⁻

Question 53

Give the general word equation for the reaction between a group 2 metal and water

Answer 53

Metal + Water Metal → hydroxide + Hydrogen

Question 54

Give the general word equation for the reaction between a group 2 metal oxide and: i) water ii) acid

Answer 54

i) Metal oxide + water → metal hydroxide | ii) Metal oxide + acid → salt + water

Question 55

Give the general word equation for the reaction between a group 2 metal hydroxide and acid

Answer 55

Metal hydroxide + acid → salt + water

Question 56

Give the general word equation for the thermal decomposition of a group 2 metal carbonate

Answer 56

Metal carbonate → metal oxide + carbon dioxide

Question 57

State the trend in reactivity with water as you go down group 2

Answer 57

The reactions become more vigorous (more reactive)

Question 58

State the trend in solubility for group 2 hydroxides as you go down the group

Answer 58

The solubility increases as you go down the group

Question 59

Give the pH of aqueous group 2 hydroxide solutions and why

Answer 59

They are alkaline since the solution contains OH⁻

Question 60

State the trend in solubility for group 2 carbonates as you go down the group

Answer 60

The solubility decreases as you go down the group

Question 61

State the trend in thermal stability for group 2 carbonates as you go down the group

Answer 61

The thermal stability increases as you go down the group

Question 62

Name the 5 main areas for a time-of-flight mass spectrometer and what condition are they all under

Answer 62

1) Sample inlet 2) Ionisation area 3) Acceleration area 4) Drift region 5) Ion detector They are all within a vacuum chamber

Question 63

Describe the sample inlet for a time-of-flight mass spectrometer

Answer 63

Where gases or liquids are injected. Solids are heated to vaporise them first

Question 64

Describe the ionisation are for a time-of-flight mass spectrometer

Answer 64

A heated filament produces high-energy electrons. These electrons bombard any atoms or molecules in the sample and knock electrons out. Cations are formed

Question 65

Describe the acceleration area for a time-of-flight mass spectrometer

Answer 65

An electric field is used to accelerate any charged particles so that they have the same kinetic energy

Question 66

Describe the drift region for a time-of-flight mass spectrometer

Answer 66

There is a vacuum here so that ions do not collide with air molecules, which would change the direction of their flight path. Since kinetic energy = 1/2 mass x velocity² and all ions have the same kinetic energy, heavier ions move slower through this region than lighter ions

Question 67

Describe the ion detector for a time-of-flight mass spectrometer

Answer 67

Light ions reach the detector before heavier ones. A computer system converts this information into a mass spectrum. Only positive ions are detected after fragmentation

Question 68

State what the x and y axis of a mass spectrum graph represents

Answer 68

x-axis: the mass to charge ratio of the different fragments (m/z) but assuming all charges are +1, this means it represents the mass of the ion detected y-axis: the % intensity (or relative abundance) for each fragment

Question 69

Define molecular ion and state how you would find it

Answer 69

The ion with the greatest mass, which corresponds with the parent molecule minus an electron It is the peak with the highest mass to charge ratio