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Chemistry may mock (mine) > paper 1 questions > Flashcards

paper 1 questions Flashcards

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1
Q

How many subatomic particles are in the 18O atom

A

8 protons 10 neutrons 8 electrons (A)

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2
Q

The mass spectrum of a sample of bromine molecules with approximately equal proportion of the 79Br amd 81 Br isotopes is

A

D one at 79 and one at 81 one big one at 160 one half the size at 158 162

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3
Q

Which isoelectronic has the largest ionic radius

A

N3-

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4
Q

How many subatomic particles are present in the phosphide ion p3-

A

15,16,18

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5
Q

Explain why a phosphorus chloride molecule has this shape and bond angle

A

Has a pyramidal shape as there are 4 pairs of electrons around the central p atom ( 3bp and 1lp) these are arranged to minimise repulsion
Bond angle is less than 109.5bas lone pair bond pair repulsion is greater than bond pair pair repulsion

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6
Q

Which describes the polarity of the p-cl bombing and the phosphorous chloride molecule

A

Polar polar (d)

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7
Q

Give the formulas and mass/ charge ratio of the ions responsible for the molecular ion peaks in the mass spectrum of pcl3

A 
Ions                            M/z 
P(cl35) 3 +                  136 
P(cl35)2 cl37+            138
pcl35 said (cl37)2+.    140
p(cl37)3+.                     142
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8
Q

the total number of electrons in all the occupied p orbitals in a chloride cl- ion is

A

12 said (was c)

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9
Q

explain why the boiling temperatures increase from chlorine to iodine

A

as you go down the group from cl to I the number of electrons increases from 17 to 53
so the strength of London forces increases / there are more London forces so more energy is needed to separate the molecules

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10
Q

by referring to any changes in oxidation numbers when these halides react with concentrated sulphuric acid , explain why the halide is the strongest reducing agent.

A

iodine ions are the strongest reducing agent because I- reduces sulphur from +6 to 0 in sulfur , where as bromide reduces sulfur from +6 to +4 . Cl ions don’t reduce sulfur as the oxidation number doesn’t change . iodine is the strongest chlorine is the weakest

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11
Q

boric acid can be prepared by reacting borax with HCl what is the equation for this reaction

A

Na2B4O7.10H2O + 2HCl >

4B(OH)3 + 2NaCl + 5H2O

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12
Q

complete the diagram of a molecule of boric acid

A

triangle and x in b-o
4 x on o
dot and x in h-o

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13
Q

what are the o-b-o and b-o-h angles in a molecule of boric acid

A

120 and 104.5

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14
Q

the glowing splint is used as a test for one of the gases given off in this experiment identify this gas and the positive result

A

oxygen and positive test = splint relights

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15
Q

give the name and the appearance of the other gas given off in this experiment when a group 2 nitrate is heated

A

nitrogen dioxide and appearance is brown

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16
Q

write the equation for the decomposition if the group 1 compound , sodium nitrate was used in this experiment

A

2NaNo3 > 2NaNo2 +O2

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17
Q

describe the apparatus that would be used to compare the decomposition of metal carbonates . include how the rate of decomposition would be compared

A

would use a delivery tube to bubble gas into limewater

compare the time taken for the limewater to go cloudy

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18
Q

explain why magnesium carbonate decomposes much more readily on heating than barium chloride

A

magnesium ion is smaller than the barium ion which polarises the large carbonate and weakens the carbon oxygen bond

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19
Q

which equation shows the third ionisation energy of aluminium

A

B. Al 2+ > Al 3+ +e-

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20
Q

which element in the table is group 2

A

C -Y

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21
Q

which letter represents the first ionisation energy of oxygen

A

C-C

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22
Q

give the formula of a stable ion that is isoelectronic with the magnesium ion mg2+

A

Na +

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23
Q

complete the table to show the numbers of subatomic particles in 6Li and 7li+

A

6Li p3 n3 e3

7Li p3 n4 e2

24
Q

deduce the formulae all the species responsible for each of the peaks on the mass spectrum

A 
species x is oxygen, each value corresponds to a different isotope 
16O=16O+ 32
16O=17O+ 33
16O=18O+ 34
17O=18O+ 35
18O=18O+ 36
25
Q

what is the maximum number of electrons which can fill each region of an atom
1s , 2p , third quantum shell

A

1s = 2
2p = 6
3rd shell = 18

26
Q

draw a dot and cross diagram to show the bonding in magnesium bromide only outer shell required

A

add a picture

27
Q

state all conditions under which magnesium bromide conducts electricity

A

molten and dissolved in water/ in aqueous solution

28
Q

excess potassium bromide was added to chlorine water and the solution turned orange write an equation for this reaction

A

Cl2 + 2KBr > Br2 +2Kcl

29
Q

silver nitrate was added to the mixture and excess dilute ammonia solution was then added only some of the precipitate dissolved. suggest why

A
  • the precipitate is a mixture of silver chloride and bromide / not all bromide ions are oxidised
  • silver chloride dissolves in dilute ammonia silver bromide doesn’t dissolve in dilute ammonia
30
Q

aqueous potassium bromide was added to aqueous iodine instead of chlorine water, there was no reaction give a reason for this

A

iodine is a weaker oxidising agent than chlorine

31
Q

chlorine undergoes disproportionation when it reacts complete the ionic equation for this reaction

A

3,5,5,na,3

32
Q

explain in terms of oxidation numbers why this is a disproportionation reaction

A

chlorine oxidation number changes from 0 to -1 so is reduced
chlorine oxidation number changes from 0 to +5 so it is oxidised

33
Q

magnesium nitrate decomposes on heating explain in terms of all relevant oxidation numbers why this is a redox reaction

A
  • N changes from +5 to +4 so is reduced. Changes from -2 to 0 so is oxidised
    redox occurs when oxidation and reduction have occurred in the same reaction
34
Q

calcium nitrate decomposes in a similar way to magnesium nitrate but requires a higher temp for decomposition. explain this observation in terms of the charge and size of the cations

A

calcium ion has a larger ionic radius than the magnesium ion so calcium ion causes less polarisation / distortion on the nitrate ion

35
Q

group 2 nitrates decompose when heated, state two observations you would see when hydrated magnesium nitrate is heated

A

solid dissolves/ melts , condensation on side of test tube, brown gas , white solid

36
Q

explain the trend in thermal stability of group 2 nitrate s

A

nitrates increase in stability down group 2 as ionic radius increases, so polarising ability of metal ion decreases , so weakening of N-O bonds is less

37
Q

in an experiment a sample of hydrated magnesium nitrate with a mass of 0.765g was dissolved in water and reacted with excess NaOH, the mass of the dried sample was 0.174g draw a dot and cross diagram for the ions of MgOH

A

add picture

38
Q

use the experimental data to calculate the value for x in the formula mg(no3)2xh2o

A

add picture

x=6

39
Q

what is the equation for the standard enthalpy change of formation of aluminium oxide

A

c) 2Al + 1/2 O2 > Al2O2

40
Q

the relevant bond enthalpies are given in the table, calculate the c-o mean bond enthalpy using the mean bond enthalpies given in the table and the enthalpy change of reaction

A

c-o = 358 kjmol-1

add picture

41
Q

which reaction has a negative value for delta system

A

a) 2cu + o2 > 2cuo

42
Q

what is the expression for delta s total

A

d) minus delta h over t

43
Q

show by calculating the value for the free energy change that this decomposition is not feasible and then calculate the minimum temperature needed for it to decompose

A

add a picture

44
Q

a buffer solution always

A

d) resits changes in PH if small quantities of acid or base are added

45
Q

a buffer solution with a ph of 3.9 is required calculate the mass in grams of sodium ethanoate that should be added to 50cm3 of an ethanoic acid solution of concentration 0.8 to form this buffer solution

A

add picture of calculation

46
Q

one of the systems controlling the ph of blood is carbonic acid-hydrogencarbonate buffer system
explain how thus buffer system helps control the ph of blood when extra co2 is present due to strenuous exercise

A

carbon dioxide dissolved in the blood form carbonic acid (so this concentration increases) the equilibrium will shift to the right to produce more H+ ions. The high concentration of hydrogen carbonate ions suppress the ionisation of carbonic acid to control ph

47
Q

draw a titration curve

A

add picture

48
Q

describe without calculation how you would use your curve to determine the value of kc

A

determine the ph at the point where half the acid is neutralised. find the ph at half the equivalence point.
ka= 10-ph

49
Q

state why the order of reaction with respect to iodide ions cannot be five even though 5 mol of iodide ions are shown in the equation

A

the chance of five or more ions colliding in the rate determining step is negligible

50
Q

in experiment 6 the student forgot to add deionised water to keep the total volume the same for each experiment state why the total volume should be kept the same

A

so the volume of iodate ions is proportional to the concentration

51
Q

iii

A

pic of graph

52
Q

deduce the order of reaction with respect to the iodate ions justify your answer

A

first order, because the straight line goes through the origin (rate is directly proportional to concentration)

53
Q

in the experiment the following data was obtained, write the rate equation. include units and give answer to appropriate sig fig (add pic of graphics)

A

rate= [h2o2][I-]
k = rate/ [h202][I-]
1.24x10-3 / (1.5 x 10-3 x2.1 x10-3) =393.65 dm3mol-1s-1

54
Q

explain the purpose of starch present in the reaction mixture when starch is neither in the rate equation nor in the reaction equation

A

starch is an indicator to react with iodine. The time taken for the formation of blue black complex can be used to calculate the reaction rate

55
Q

Arrhenius equation

A

picture of calculation

56
Q

give a reason for the point at in k=- -7 not being included in the line being drawn on the graph

A

it is an anomaly / anomalous point

Chemistry may mock (mine) (3 decks)

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