paper 1 questions Flashcards by Holly Langston

How many subatomic particles are in the 18O atom

8 protons 10 neutrons 8 electrons (A)

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

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

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Which isoelectronic has the largest ionic radius

N3-

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

15,16,18

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

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

Polar polar (d)

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

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

12 said (was c)

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explain why the boiling temperatures increase from chlorine to iodine

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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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.

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

Na2B4O7.10H2O + 2HCl >

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

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complete the diagram of a molecule of boric acid

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

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

120 and 104.5

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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

oxygen and positive test = splint relights

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

nitrogen dioxide and appearance is brown

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

2NaNo3 > 2NaNo2 +O2

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

would use a delivery tube to bubble gas into limewater

compare the time taken for the limewater to go cloudy

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

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

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which equation shows the third ionisation energy of aluminium

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

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which element in the table is group 2

C -Y

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which letter represents the first ionisation energy of oxygen

C-C

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

Na +

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

6Li p3 n3 e3

7Li p3 n4 e2

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

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

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

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

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

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state all conditions under which magnesium bromide conducts electricity

molten and dissolved in water/ in aqueous solution

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

Cl2 + 2KBr > Br2 +2Kcl

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

- 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

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

iodine is a weaker oxidising agent than chlorine

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

3,5,5,na,3

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

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

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

- 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

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

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

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

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

explain the trend in thermal stability of group 2 nitrate s

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

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

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

add picture x=6

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

c) 2Al + 1/2 O2 > Al2O2

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

c-o = 358 kjmol-1 | add picture

which reaction has a negative value for delta system

a) 2cu + o2 > 2cuo

what is the expression for delta s total

d) minus delta h over t

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

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a buffer solution always

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

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

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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

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

draw a titration curve

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

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

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

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

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

so the volume of iodate ions is proportional to the concentration

iii

pic of graph

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

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

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)

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

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

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

Arrhenius equation

picture of calculation

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

it is an anomaly / anomalous point