Cambridge IGCSE Chemistry - 0620 - Core Paper 3 2012 Winter Zone 1

The diagram shows the structures of five compounds, A, B, C, D, and E, containing carbon.


(a) Answer these questions using the letters A, B, C, D, or E.
Each compound can be used once, more than once or not at all.
Which one of these compounds
(i) is an unsaturated hydrocarbon, .......................................................... [1]
(ii) is a product of the complete combustion of a hydrocarbon, .......................... [1]
(iii) belongs to the alcohol homologous series, .............................................. [1]
(iv) is an alkane, ......................................................................................... [1]
(v) is a product of respiration, ................................................................. [1]
(vi) is a product of fermentation? ............................................................. [1]

(b) Write the molecular formula of compound C. .................................................... [1]

(c) Compound B is inert to most chemical reagents.
It is made by reacting chlorine with carbon disulfide in the presence of an aluminium chloride catalyst.
What do you understand by the following terms?
compound ..................................................................................................... [1]
...................................................................................................................
inert ............................................................................................................ [1]
...................................................................................................................
catalyst ........................................................................................................ [1]
...................................................................................................................

Hydrogen chloride, HCl, is an acidic gas.

(a) Draw a dot and cross diagram of a molecule of hydrogen chloride.
Show only the outer electrons.

(b) Hydrogen chloride dissolves in water to form a solution of hydrochloric acid. A student titrated aqueous ammonia with hydrochloric acid using the apparatus shown below.

(i) State the name of the pieces of apparatus labelled A and B.
A is a ................................................................. [1]
B is a ................................................................. [1]
(ii) Describe how the pH value of the solution in B changes as hydrochloric acid is added until the acid is in excess.
.......................................................................................
.......................................................................................
....................................................................................... [3]
(iii) Complete the word and symbol equations for this reaction.
ammonia + hydrochloric acid → ................................................
.......... + HCl → NH₄Cl [2]

(c) Aqueous ammonia is used to test for copper(II) ions. Describe what happens when you add aqueous ammonia to a solution of copper(II) sulfate until the aqueous ammonia is in excess.
.......................................................................................
.......................................................................................
.......................................................................................
....................................................................................... [4]

(a) (i) Use the results in the table to suggest the order of reactivity of the metals iron, lead, magnesium and zinc.
most reactive ____________________________ least reactive [2]

(a) (ii) Predict whether iron will react with zinc oxide. Explain your answer.
..................................................................................................................................................
.................................................................................................................................................. [1]

(b) Which two of the following statements about metals are correct? Tick two boxes.
Metals conduct electricity and heat.
All Group IV elements show metallic properties.
Magnesium is extracted by heating its oxide with carbon.
All metals have high densities.
Iron is a transition element. [2]

(c) (i) Describe the arrangement and movement of the particles in a solid.
arrangement .................................................................................................................................
movement .................................................................................................................................. [2]

(c) (ii) Describe how you could separate the sand from a mixture of sand and salt. Give full details of how this is carried out.
..................................................................................................................................................
..................................................................................................................................................
.................................................................................................................................................. [3]

(d) Complete the following sentences about this separation using words from the list below.
condenser, crystallisation, distillation, flask, heavy, higher, lower, solid, volatile, vapour
Fractional ............................. is used to separate a mixture of water and ethanol. The temperature at the top of the fractionating column is ............................. than the temperature at the bottom. The more ............................. liquid evaporates and moves further up the column. It eventually reaches the ............................. where the ............................. changes to a liquid. [5]

Lithium has two naturally-occurring isotopes, $^6_3$Li and $^7_3$Li.
(a) What do you understand by the term isotope?
.........................................................................................................................................
......................................................................................................................................... [1]
(b) Draw a labelled diagram to show the atomic structure of an atom of $^7_3$Li.
Show the particles in the nucleus as well as the electrons. [5]
(c) Lithium reacts with oxygen to form lithium oxide, Li$_2$O.
Complete the equation for this reaction.
......Li + ........ $ ightarrow$ ......Li$_2$O [3]
(d) Aqueous lithium chloride is electrolysed using the apparatus shown below.

(i) On the diagram above, label:
• the electrolyte
• the anode. [2]
(ii) What do you understand by the term aqueous?
......................................................................................................................................... [1]
(iii) Explain why aqueous lithium chloride is able to conduct electricity.
......................................................................................................................................... [1]

(a) Match the fuel on the left with the information on the right. The first one has been done for you.



(b) Two students investigated some fuels to find which gave off the most energy. They tested four liquid fuels using the apparatus shown below.



(i) In each experiment, the amount of fuel burnt was the same. Suggest one other factor that should be kept the same in each experiment.
.............................................................................................................................................................. [1]
(ii) The students used the thermometer to stir the water. Suggest why it is important to keep the water stirred.
.............................................................................................................................................................. [1]
(iii) The results are shown in the table below.

[Table_1]

Which fuel transfers the most energy to the water? Explain your answer.
.............................................................................................................................................................. [2]

(c) Air is needed for fuels to burn. The pie chart below shows the composition of the air.



State the name of
gas A, ......................................................................................................................................
gas B. ....................................................................................................................................... [2]

(d) Argon is a noble gas.

(i) State one use for argon.
.............................................................................................................................................................. [1]
(ii) To which period in the Periodic Table does argon belong?
.............................................................................................................................................................. [1]
(iii) Describe the chemical properties of argon.
.............................................................................................................................................................. [1]

A student placed a crystal of silver nitrate and a crystal of potassium iodide in a dish of water. After an hour she observed that
• the crystals had disappeared,
• a yellow precipitate had appeared near the middle of the dish.



(a) Use your knowledge of the kinetic particle theory and reactions between ions to explain these observations.
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................
............................................................................................................................ [4]

(b) Potassium iodide reacts with aqueous chlorine. Complete the equation for this reaction.

2KI + ........ -> ......KCl + I_2 [2]

The diagram shows one molecule of sulfur.
(a) How many atoms are there in three molecules of sulfur? ................................................................................................................................................................. [1]
(b) Calculate the relative molecular mass of sulfur.
[1]
(c) Explain how acid rain is formed when fossil fuels containing sulfur are burnt. In your answer, include
● the name of a fossil fuel which contains sulfur,
● the gas formed when sulfur burns,
● the reactions which lead to the formation of acid rain.
..................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... [4]
(d) Potassium sulfate can be used as a fertiliser. The potassium in this fertiliser is an important element for plant growth. Name two other elements, important for plant growth, which are present in most fertilisers.
.................................................... and .................... and .................................................... [2]
(e) Describe a test for sulfate ions.
test ...................................................................................................................................
result ............................................................................................................................... [2]