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OCR A-Level Chemistry Henry K > Module 2 - Foundations in Chemistry - Exam Questions > Flashcards

Module 2 - Foundations in Chemistry - Exam Questions Flashcards

1
Q

Define relative isotopic mass (2)

A

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

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2
Q

Define isotopes (1)

A

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

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3
Q

Explain why isotopes have the same chemical properties (1)

A

Same number of electrons in the outer shell

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4
Q

Define relative atomic mass (3)

A

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

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5
Q

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

A

Mass spectrometry

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6
Q

Explain what is meant by a salt (1)

A

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

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7
Q

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

A

Waters of crystallisation

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8
Q

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

A

Calcium hydroxide

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9
Q

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

A

Calcium nitrate

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10
Q

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

A

MgO has reacted with CO2

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11
Q

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

A

Solid dissolves

Effervescence

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12
Q

Define an acid (1)

A

A proton donor

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13
Q

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

A

CaCO3 neutralises HCl

CaCO3 + 2HCl -> CaCl2 + H2O + CO2

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14
Q

State an important use of ammonium sulphate (1)

A

Fertiliser

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15
Q

State a large-scale use of ammonia (1)

A

Manufacture of explosives

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16
Q

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

A

Loss of electrons

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17
Q

What is meant by the term mole? (1)

A

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

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18
Q

What is a common use of NaClO? (1)

A

Bleach

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19
Q

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

A

Ca has reacted with water

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

20
Q

Explain what is meant by molecular formula (1)

A

Number and type of atoms making up a molecule

21
Q

What is meant by ionic bonding? (1)

A

Electrostatic attraction between oppositely charged ions

22
Q

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

A

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

23
Q

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

A

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

24
Q

What is meant by a covalent bond? (1)

A

A shared pair of electrons

25
Q

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

A

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

26
Q

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

A

Ions cannot move in a solid

Ions can move in solution

27
Q

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

A

No hydrogen bonding

Weaker intermolecular forces

28
Q

What is meant by hydrogen bonding? (1)

A

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

29
Q

Explain electronegativity (2)

A

Attraction of an atom for electrons in a covalent bond

30
Q

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

A

Oxygen and nitrogen are more electronegative than hydrogen

31
Q

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

A

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

32
Q

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

A

CO2 is symmetrical

In CO2, dipoles cancel

33
Q

State the ON’s H202

A 
H = -2 
O = -2
34
Q

State the ON’s for Ca(ClO4)2

A

Ca= +2
Cl= +7
O=-2

35
Q

State the ON’s for BrF5

A

Br=+5

F=-1

36
Q

State the ON’s for BrO3

A

Br=+6

O=-2

37
Q

State the ON’s for CaO

A

Ca=+2

O=-2

38
Q

State the ON’s for CuI

A

Cu=+1

I=-1

39
Q

State the ON’s for FeBr3

A

Fe=+3

Br=-1

40
Q

State the ON’s for NH4Cl

A

N=-3
H=+1
Cl=-1

41
Q

State the ON’s for KClO3

A

K=+1
Cl=+5
O=-2

42
Q

State the ON’s for H2P2O7

A

H=+1
P=+6
O=-2

43
Q

State the ON’s for (NO2)-

A

N=+3

O=-2

44
Q

State the ON’s for ZnH2

A

Zn=+2

H=-1

45
Q

State the ON’s for KCl

A

K=+1

Cl=-1

46
Q

State the ON’s for O3

A

0

47
Q

The element strontium forms a nitrate, Sr(NO3)2, which decomposes on heating as
shown below.

2Sr(NO3)2(s) → 2SrO(s) + 4NO2(g) + O2(g)

(i) Using oxidation numbers, explain why the reaction involves both oxidation and
reduction.

A

N changes from +5 in 2Sr(NO3)2 to +4 in 4NO2, therefore its Reduced.

O changes from -2 in 2Sr(NO3)2 to 0 in O2, therefore its Oxidised.

OCR A-Level Chemistry Henry K (35 decks)

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