edexcel a level chemistry unit 5 paper jun 2000

8/16/2019 EdExcel a Level Chemistry Unit 5 Paper Jun 2000

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1. The species X, Y and Z are atoms or ions.

species X Y Z

atomic number 16 16 16

mass number 32 35 32

net charge 0 0 –2

(a) (i) State the number of electrons, protons and neutrons X

electrons .......................... protons ......................... neutrons .......................(1)

(ii) What is the relationship between X and Y?

……………………………………………………………………………..…(1)

(iii) Identify Z

……………………………………………………………………………..…(1)

(b) 332 kJ of energy are required to convert a mole of gaseous atoms of X to a mole of

gaseous Z

(i) Represent by equations the two steps which make up this energy change.

……………………………………………………………………………..…

……………………………………………………………………………..…(2)

(ii) Explain why the second step is endothermic

……………………………………………………………………………..…

……………………………………………………………………………..…(1)

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(c) Y is radioactive, decaying by beta (❜

) emission.

When a sample of the product form the❜

decay of Y was passed into a mass spectrometer

it produced only one peak, at m/e = 35 whereas a naturally occurring sample of thiselement gave an extra peak at m/e = 37.

Account for this difference between the sample of the element made from Y and the

naturally occurring sample of the same element.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 8 marks)

2. (a) Consider the following elements

Carbon, iron, lead, magnesium, phosphorus, sodium.

In each case choose ONE of these elements which fits the description given.

(i) This element has a carbonate which will easily decompose on heating with aBunsen burner

……………………………………………………………………………..…(1)

(ii) This element and its compounds act as catalysts

……………………………………………………………………………..…

(1)

(iii) This element has an oxide which reacts with water to form a solution of pH less

than 6

……………………………………………………………………………..…(1)

(iv) This element has a white hydroxide which is sparingly soluble in water.

……………………………………………………………………………..…(1)

(v) This element has a +4 oxidation state which can be reduced to the +2 oxidation

state.

……………………………………………………………………………..…(1)

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(b) State which element in the whole Periodic Table has the largest first ionisation energy.

Justify your choice

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(c) (i) What is meant by the term polarising power as applied to cations?

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(ii) Give TWO factors which affect the polarising power of cations.

...........................................................................................................................(2)

(iii) Using the ideas outlined above suggest whether you would expect anhydrous

calcium chloride or anhydrous magnesium chloride to have the more covalent

character.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(Total 14 marks)

3. Consider the following data for the hydrides of the Group 4 elements.

element formula of

hydride

boiling temperature

/K

relative molecular

mass

carbon CH4 109 16

silicon SiH4 161 32

germanium GeH4 185 77

tin SnH4 221 123

lead PbH4 ➽ ➽

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(a) Represent the trend in the boiling temperature with relative molecular mass for these

hydrides.

Boilingtemperature

/K

350

300

250

200

150

100

50

00 50 100 150 200 250

Relative molecular mass

(2)

(b) (i) Account for the increase in boiling temperature as the relative molecular massincreases.

............................................................................................................................

............................................................................................................................(2)

(ii) Use your diagram in (a) to suggest a likely value for the boiling temperature of

PbH4.

............................................................................................................................(1)

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(iii) PbH4 is actually thermally unstable and unlikely to have the boiling temperature

you have suggested. Suggest why PbH4 is thermally unstable

............................................................................................................................

............................................................................................................................(2)

(c) Predict the shape of a molecule of SiH4 and justify your prediction.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(d) (i) Define the term first ionisation energy.

............................................................................................................................

............................................................................................................................(2)

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(ii) The successive ionisation energies of silicon are given in the table below.

number of ionisation ionisation energy/kJ mol-1

1 789

2 1580

3 3230

4 4360

5 16100

6 19800

7 23800

8 29200

9 33900

10 38800

11 45900

12 505000

13 235000

14 258000

Use these data to deduce the electronic structure of silicon.

............................................................................................................................

............................................................................................................................

............................................................................................................................(2)

(Total 14 marks)

4. Consider the reaction scheme shown below.

Fe(s)metal

FeCL (s)black

Fe(OH) (s)red-brown solid

FeSO (aq)pale greensolution

Fe(OH) (s)green precipitate

step 3

reaction with air

step 1 step 2

step 4

2

3 3

4

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(a) (i) Identify one of the steps in the scheme which is a redox reaction and give the

starting and finishing oxidation numbers for iron.

Step ...................................................................................................................

From ................................................................... To .......................................(2)

(ii) Suggest a suitable reagent for step 1 and write the ionic equation for the reaction.

Reagent .............................................................................................................

Equation ............................................................................................................(2)

(iii) Suggest a suitable reagent for step 2 and explain how this is a deprotonation

reaction.

Reagent .............................................................................................................

Explanation .......................................................................................................

............................................................................................................................

............................................................................................................................(3)

(iv) State ONE factor which is important in enabling ionic compounds such as FeSO4 tobe soluble in polar solvents such as water.

............................................................................................................................(1)

(v) State TWO characteristic properties of transition metals which are illustrated in thescheme above.

............................................................................................................................

............................................................................................................................(2)

(b) A sample of Fe(OH)2 was left in air until some had changed to Fe(OH)3.

The amount of iron(II) hydroxide remaining may be determined by reacting the solid with

excess sulphuric acid and then titrating the resulting acidic solution with a standardpotassium manganate (VII) solution.

Fe(OH)2(s) + 2H+(aq)

➤

Fe2+(aq) + 2H2O(l)

5Fe2+(aq) + MnO–4 (aq) + 8H+(aq) ➤ 5Fe3+(aq) + Mn2+(aq) + 4H2O(l)

4.00g of the hydroxide mixture was reacted with excess sulphuric acid and the solution

made up to 250cm3. A 25.0 cm3 sample of this solution was titrated with acidified

potassium manganate (VII) solution of concentration 0.0200 mol dm-3. 37.5cm3 ofpotassium manganate (VII) solution was required for complete reaction.

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Calculate:

(i) the number of moles of manganate (VII) ions used.

(1)

(ii) the number of moles of iron(II) ions in 25.0cm3 of solution

(1)

(iii) the number of moles of iron(II) ions in the solid mixture of hydroxides.

(1)

(iv) the percentage of Fe(OH)2 in the mixture

(2)

(Total 15 marks)

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edexcel a level chemistry unit 5 paper jun 2000

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