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Chemistry A level OCR A > Module 2 > Flashcards

Module 2 Flashcards

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1
Q

Define ionic bonding

A

Electrostatic attraction between positive and negative ions.

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2
Q

Draw a dot and cross diagram for sodium chloride

A
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3
Q

What sort of structure do ionic compounds have, and what causes them to have this structure?

A

Giant ionic lattices; Results from oppositely charged ions strongly attracted in all directions.

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4
Q

Explain why the melting and boiling points of ionic compounds are usually very high.

A

For the electrostatic attraction in a giant ionic lattice is very strong and requires a lot of energy to break this attraction.

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5
Q

Explain how ionic substances can dissolve.

A

An ionic substance will dissolve by the reaction of polar substances’, e.g. Water, ∂+ and ∂- charges interacting and surrounding positive or negative ions.

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6
Q

Describe and explain the electrical conductivity of ionic compounds

A

In a solid, the ions are fixed, so doesn’t conduct electricity; however, in a liquid or aqueous state, the ions are not fixed, so can move and carry charge, so can conduct electricity.

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7
Q

Define covalent bonding

A

The strong electrostatic attraction between a shared pair of electrons.

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8
Q

Draw a dot and cross diagram for hydrogen fluoride

A
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9
Q

Draw a dot and cross diagram for carbon dioxide

A
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10
Q

Draw a dot and cross diagram for ammonia

A
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11
Q

Draw a dot and cross diagram for ammonium ion

A

***ATTACHPICTURE***

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12
Q

What is average bond enthalpy?

A

A measurement of covalent bond strength

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13
Q

Define electronegativity

A

The ability of an atom to attract the bonding electrons in a covalent bond to itself

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14
Q

Describe the trend of electronegativity in elements.

A

Generally, the electronegativity in elements increases the closer to fluorine it is in the periodic table.

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15
Q

Define a polar bond

A

A permanent dipole caused within a molecule by two atoms of a difference in electronegativity between 0.5 and 1.7

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16
Q

Define a polar molecule

A

A molecule with will have polar bonds, but these polar bonds must cause an overall dipole, which is down to permanent dipoles and molecular shape

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17
Q

What are intermolecular bonds based on?

A

Permanent dipole-dipole interactions and induced dipole-dipole forces/London forces (van der Waals’ forces)

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18
Q

Define hydrogen bonding

A

Intermolecular bonding between molecules containing an N,O or F atom bonded to hydrogen in a polar atom

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19
Q

Describe and explain the anomalous properties of water.

A

Due to its hydrogen bonding, the density of its solid (ice) is less than that of its liquid and it has relatively high melting and boiling points.

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20
Q

Define an isotope

A

Atoms of the same element with different numbers of neutrons and different masses.

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21
Q

Define relative isotopic mass

A

The mass of an isotope compared with 1/12th mass of carbon-12

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22
Q

Define relative atomic mass

A

The weighted mean mass compared of an atom with 1/12th mass of carbon-12)

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23
Q

Describe how mass spectrometry can be used to determine the relative isotopic mass of a sample

A

As the graph gives mass/charge and all ions are assumed to be have a charge of 1+, each peak on the graph represents the relative abundances of each isotope present, and each m/q value is the isotopic masses present.

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24
Q

Describe how to calculate the relative atomic mass from a graph output from a mass spectrometer.

A

Take a weighted average of each isotope present.

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25
Q

Predict the charge of a Lithium ion based on its position in the periodic table.

A

Li^+, as it is in group one.

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26
Q

Predict the charge of an Aluminium ion based on its position in the periodic table.

A

Al^3+, as it is in group three.

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27
Q

What is the charge of a Nitrate ion?

A

NO_3^-

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28
Q

What is the charge of a Carbonate ion?

A

CO_3^2-

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29
Q

What is the charge of a Sulfate ion?

A

SO_4^2-

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30
Q

What is the charge of a Hydroxide ion?

A

OH^-

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31
Q

What is the charge of an Ammonium ion?

A

NH_4^+

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32
Q

What is the charge of a Zinc ion?

A

Zn^2+

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33
Q

What is the charge of a Silver ion?

A

Ag+

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34
Q

Give the simplistic definition of an acid

A

A substance which releases H^+ ions in aqueous solution

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35
Q

Give the simplistic definition of an alkali

A

A substance which releases OH^- ions in aqueous solution

36
Q

Give the formula for Hydrochloric Acid

A

HCl

37
Q

Give the formula for Sulfuric Acid

A

H_2SO_4

38
Q

Give the formula for Nitric Acid

A

HNO_3

39
Q

Give the formula for Phosphoric Acid

A

H_3PO_4

40
Q

Give the formula for Ethanoic Acid

A

CH_3COOH

41
Q

Describe the difference between a strong and weak acid

A

The stronger the acid, the more it will have dissociated in water, with strong acids being fully dissociated in water.

42
Q

Describe a neutralisation reaction, in terms of ions.

A

H^+ and OH- forming H_2O

43
Q

Give the word equation for an acid and base reaction

A

Acid + Base —> Salt + Water

44
Q

What is the differences between an acid reacting with a base than with a carbonate?

A

Carbon dioxide is given off when reacting with carbonate, but not a base

45
Q

Describe how make a standard solution

A

The solid is first weighed accurately; The solid is dissolved in a beaker using distilled water; It is then transferred to a volumetric flask, with the last traces of solution from the beaker rinsed into the flask; Distilled water should then be added until the bottom of the meniscus just touches the bottom of the graduation line; The flask is then inverted several times to properly mix the solution.

46
Q

Where is the sign placed for an oxidation number

A

Before the number

47
Q

What is the oxidation number for elements?

A

0

48
Q

What is the magnitude of the oxidation number of Iron(III)?

A

+3

49
Q

What is a redox reaction in terms of oxidation numbers?

A

Where the net change is zero

50
Q

What is reduction in terms of oxidation numbers?

A

Decrease in oxidation number

51
Q

What is oxidation in terms of oxidation numbers?

A

Increase in oxidation number

52
Q

What is oxidation in terms of electron transfer?

A

Loss of electrons

53
Q

What is reduction in terms of electron transfer?

A

Gain of electrons

54
Q

What is the word equation of the redox reactions of acids?

A

Metal + Acid —> Salt + Hydrogen

55
Q

Work out the atomic mass for chlorine given the results from the graph below

A

((1.5*37)+(5*35))/(1.5+5) = 35.5 amu

56
Q

Calculate the amount of substance of 96.0g of Carbon

A

m = 96.0g

M = 12.0 amu

n = ?

n = m/M

n = 96/12 = 8.0 mol

57
Q

Calculate the mass, in g, of 0.050 mol of NO_2

A

n = 0.050 mol

M = 46.0 amu

m = ?

n = m/M —> n*M = m

m = 0.05*46 = 2.3g

58
Q

Chemical analysis of a compound by mass gave the percentage composition by mass C: 40.00%, H: 6.67% and O: 53.33%. The relative molecular mass of the compound is 180.0 amu. Determine the emperical formula and hense, or otherwise, determine the molecular formula.

A

n(C) = 40.00/12 = 3.33 mol

n(H) = 6.67/1 = 6.67 mol

n(O) = 53.33/16 = 3.33 mol

Smallest whole number ration is 1:2:1

So emerpicical formual CH_2O

180/(12+2+16) = 6, so there are six lots of the ratio per molecule.

Therefore molecular formula = C_6H_12O_6

59
Q

Define anhydrous

A

Containg no water molecules

60
Q

Define Hydrated

A

A crystalline compound containing water molecules

61
Q

Define Water of Crystallisation

A

Water molecules that are bonded into a crystalline structure of a compound

62
Q

Describe an experiment to determine the water of crystallisation in hydrated salts

A
  • Weigh an empty crucible
  • Add the hydrated salt into the weighed crucible and weigh again
  • Using a pipe clay triangle, support the crucible on a tripod and heat gently for about a minute, then strongly for around three
  • Leave to cool and re-weigh the crucible
63
Q

Explain two assumptions of the experiment to determine water of crystallisation.

A

All the water has been lost - it can be easy to tell if the salts are different colours, but you can still only see the surface crystals adn some water could be left inside. A way to counteract this is to way until constant mass.

No further decompositon - Many salts decompose further when heated, so will not give accurate results

64
Q

Calculate the mass of Na_2CO_3 required to prepare 100cm^3 of a 0.250 mol/dm^3 standard solution

A

n = ?

c = 0.250 mol/dm^3

v = (100x10^-3) dm^3

n = cv. n = 0.250*(100x10^-3) = 0.0250 mol

M = 23+23+12+16+16+16=106.0 g/mol

m = ?

n = m/M so m = nM. m = 0.0250*106.0 = 2.65g

65
Q

Calculate the amount in mol of hydrogen gas (H_2) in 480 cm^3 at RTP

A

At RTP, n = V/24

n = ?

V = 0.480 dm^3

n = 0.480/24 = 0.0200 mol of H_2

66
Q

What is the ideal gas equation?

A

pV = nRT, where…

p = pressure in Pa (or in kPa)

V = Volume in m^3 (or in dm^3)

n = amount of gas molecules in mol

R = ideal gas constant (given on data sheet as 8.314 J/mol K

T = Temperature in K

67
Q

Using the idea gas equation, find out the conditions that give a molar gas volume of 24.0 dm^3/mol, assuming that the pressure is 101kPa.

A

p = 101 kPa

V = 24 dm^3 (the units for the two above can either both be converted to m^3 and Pa, or stay as dm^3 and kPa)

n = 1 mol

R = 8.314 J/mol K

pV = nRT —> T = (pV)/nR. T = ((101)*(24))/((1)*(8.314) = 292 K = 19 degrees C

68
Q

What are the assumptions for the molecules making up an ideal gas?

A
  • Random motion
  • Elastic Collisions
  • Negligible size
  • No intermolecular forces
69
Q

What is the conversion between Kelvin and Celcius?

A

K - 273 = C

70
Q

Calculate the percentage yield when 1.150g of sodium reacts with an excess of chlorine, forming 1.872g of sodium chloride.

A

n(Na) = ?

m = 1.150g

M = 23.0 g/mol

n = m/M. n = 1.150/23.0 = 0.0500 mol

Using stoichiometric relationships…

2Na + Cl_2 —> 2NaCl

I 0.05 0

C -0.05 +0.5

E 0 0.05

So theoritical yield of NaCl = 0.0500 mol

Actual yield:

n(NaCl) = m/M

m = 1.872

M = 23 + 35.5 = 58.5 g/mol

n = 1.872/58.5 = 0.0320mol

Percentage yield = (Actual/Theortical)*100

Yield = (0.0320/0.0500)*100 = 64.0%

71
Q

Explain the importance of the limiting reagent

A

The reactant which is not in excess will be completely used up, so this reagent will allow us to be able work out how many moles have reacted in the reaction.

72
Q

Define atom economy

A

A measure of how well atoms have been utilised

73
Q

Work out the atom economy of hydrogen from the equation below:

C + 2H_2O — > 2H_2 + CO_2

Explain how sustainable you feel this reaction is

A

M(2H_2) = 2*2.0 = 4.0 g/mol

M(CO_2) = 12.0+16.0+16.0 = 44.0 g/mol

Atom Economy = M(desired)/M(all)

AE = 4/4+44 = 8.3%

The overall yield will mean that not much product will actually be produced and the other product is contributing towards global warming;

However, The process uses reactants which are readily available, and carbon dioxide is used in other processes.

74
Q

How many electrons can fill the first 4 shells?

A

Shell 1 = 2

Shell 2 = 8

Shell 3 = 18

Shell 4 = 32

75
Q

Describe the layout of the orbitals in the first four shells

A

Shell 1 = 1s

Shell 2 = 2s + 2p

Shell 3 = 3s + 3p + 3d

Shell 4 = 4s + 4p + 4d + 4f

76
Q

Describe the shape of the S-orbital and how many are found in each shell.

A

One S-orbital is found within each energy level and is the shape of a sphere

77
Q

What is the shap of a p-orbital, and how many are present in each shell from shell two onwards?

A

There are three sub shells in each shell from shell two and they are within the shape of a ‘dumb-bell’

78
Q

How many d-orbitals are present in each shell (3&4)?

A

There are 5 orbitals present

79
Q

How many f-orbitals are present in the fourth shell?

A

There are seven orbitals present

80
Q

Define an atomic orbital

A

A region around the nucleus which can hold up to electrons with opposite spins.

81
Q

What is the electron configuration for Oxygen?

A

1s2 2s2 2p4, with 2p having only one full orbital

82
Q

What is the electron configuration for copper?

A

1s2 2s2 2p6 3s2 3p6 3d10 4s1

83
Q

What is the shape and bond angle for an atom with two electrons pairs around a central atom?

A

Linear and 180 degrees

84
Q

What is the shape and bonding angle of a molecule with three electrons pairs around a central atom?

A

Trigonal planar and 120 degrees

85
Q

What is the shape and the bond angle of a molecule with four electron pairs around a central atom

A

Tetrahedral and 109.5 degrees

86
Q

What is the shape and bond angle for a molecule with six electrons pairs around a single atom?

A

Octahedral and 90 degrees

Chemistry A level OCR A (5 decks)

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