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A Level > Chemistry past paper corrections 2017 > Flashcards

Chemistry past paper corrections 2017 Flashcards

1
Q

What is and isn’t an isotope?

A

Where it has the same number of protons but a different number of neutrons
An isotope can be the same as the normal amount given on periodic table

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2
Q

How do aqueous transition metals react with bases?

A

They donate an H+ off of their H2O ligand to the OH- ion from the base to leave OH- ligand attached to the transition metal

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3
Q

What is a rule about mole fractions?

A

They always add up to 1

They are basically a percentage of the whole mole

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4
Q

What is the shape of a molecule with 4 bonds?

A

Tetrahedral

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5
Q

What is the shape of a molecule with two bonds and two lone pairs?

A

Non-linear

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6
Q

Why do boiling points of simple covalent molecules increase down the group?

A

Because they’ve got more electrons

So they have more/stronger London forces

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7
Q

Why does reactivity down group 2 increase?

A

Because there is more electron shielding
Electrons are less attracted to the nucleus
Ionisation energy decreases
Less energy is needed to remove an electron

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8
Q

What does systematic name mean and what does it need?

A

Name of a molecule and it needs the oxidation number of the molecule
eg potassium dichlorate needs (VII) which is the oxidation number of chlorine in KClO4

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9
Q

What is an easy mistake that you can make when writing any equation to do with enthalpy?

A

It is always going to 1 mole of the product, so dont write

Br2 —-> 2Br, write 1/2 Br2 —> Br

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10
Q

What must you write when explaining the entropy change?

A

That —– has more/less disorder

eg. there is a solid in the products which has less disorder

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11
Q

What is the charge on NO3?

A

-1

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12
Q

What is the link between a graph and Gibbs free energy?

A

The equation for Gibbs free energy can be linked to y=mx+c

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13
Q

How must you write Kp?

A

With round brackets, NOT SQUARE

p —–

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14
Q

What does it mean when it says indicate the scale of working?

A

Write the actual volume of the apparatus eg. 1000 cm3 or 1 dm3

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15
Q

How can the rate of reaction be measured?

A

By measuring the loss of mass

By measuring the amount of gas given off

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16
Q

What are the units for the rate constant from ln2/half life?

A

s-1

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17
Q

When talking about equilibrium, what must be specified?

A

The direction of the reaction

eg. the FORWARD reaction is endothermic

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18
Q

Why is low pressure or low temperature not used as conditions?

A

Because there is a slow rate of reaction

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19
Q

Why is high temperature not used as conditions?

A

Because it uses a large amount of fuel

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20
Q

Even if you think you got the question wrong, what do you need to check?

A

Significant figures and units

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21
Q

When working out conjugate acid base pairs, what do you need to do?

A

Work out which one is more likely to lose a hydrogen

  • Look at Ka values, higher one is stronger acid
  • Look to see if there is an electronegative group on it which will make it more stable when dissociated
22
Q

If volume of a buffer solution increases, what will happen to the Ka value?

A

Stay the same because proportion of HA/A- is the same

23
Q

What needs to be watched out for when taking about oxidation and reduction in standard electrode potentials?

A

Reducing agent = oxidised

Oxidising agent = reduced !!!

24
Q

What is the formula of the blue precipitate formed when NH3 is added to [Cu (H2O)6 ]2+ solution?

A

Cu(OH)2
Because H2O loses an H+ to become OH- ligands
This is not ligand substitution yet

25
Q

What is the formula of the deep blue solution formed when excess NH3 is added to [Cu (H2O)6 ]2+ solution?

A

Redissolves
[Cu (NH3)4 (H2O)2 ]2+
Ligand substitution

26
Q

What happens when you add a salt like KI to a transition metal ion?

A

You get CuI and I2, which is a redox reaction, and forms a white precipitate and a brown solution

27
Q

What counts as a H NMR environment which can often be missed?

A

The hydrogen on the OH group

28
Q

What is the most acidic- amide, carboxylic acid, ester or acyl chloride?

A

Acyl chloride

29
Q

Why does a branched compound have a lower boiling point to an unbranched compound?

A

Because there are less points of contact
Less surface interaction
Less London forces can form
Less energy is needed to break the London forces

30
Q

What is the definition of stereoisomers?

A

Molecules that have the same structural formula but a different arrangement in space

31
Q

How does a molecule act as an electrophile?

A

It accepts a pair of electrons/lone pair

32
Q

Why is one of the products of electrophilic addition a major product?

A

Because the carbocation intermediate is more stable (the one with the + on it) when the hydrogen bonds to the carbon with the most hydrogens on it

33
Q

When working out the percentage yield, what do you use?

A

The moles, not the mass

34
Q

How do you check the purity?

A

Melt in a capillary tube
Find the melting point
Compare to known values
If it is a sharp melting point close to the known value, it is pure

35
Q

How does an electron donating group work?

A

It donates a PAIR of electrons/LONE PAIR into the benzene ring
or
It is DELOCALISED into the benzene ring

36
Q

When is a halogen carrier needed?

A

When it is a benzene or when there is an electron withdrawing group

37
Q

What is the product when an amine reacts with an acid?

A

NH3+Cl-

38
Q

What is the structure of a hydrogen bond?

A

The H on the H2O binds to the lone pair on the O on the molecule.
Make sure the LONE PAIR is included

39
Q

How do you name aromatic compounds?

A

Cyclo-

eg. 3-methylcyclohexanol

40
Q

When talking about oxidation of alcohols to aldehydes, what should you write instead of heat?

A

Distillation

41
Q

What is a property of cyclohexane?

A

It is weakly acidic

42
Q

When asked to analyse H NMR what must you do?

A

Write out the information fully, describing where on the spectrum the peak is, whether it is a singlet etc. and how many hydrogens it has.

43
Q

What is the bonding and shape of H2O

A

H2O has two bonded pairs and 2 lone pairs so it forms a tetrahedral structure shape which is nonlinear with 104.5 degrees

44
Q

What is 1 m3 in dm3?

A

1000 dm3

45
Q

What can methane be used for in industries?

A

Fuel

46
Q

What do yo always need to do when doing Hess cycles?

A

Draw it out!

47
Q

What are the units for rate in a rate equation?

A

mol dm-3 s-1

48
Q

What is the amount of error that you use when working out which titres to use to work out the mean titre?

A

Within 0.1 cm3 of each other

49
Q

What can you work out from the amount of optical isomers there are?

A

The amount of chiral centres

eg. 4 optical isomers = two chiral centres

50
Q

What happens when a carboxylic acid reacts with magnesium?

A

Magnesium is a group two metal so it will put brackets and 2 around the COO- part

A Level (25 decks)

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