Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2022 Summer Zone 2

The symbols of the elements of Period 3 of the Periodic Table are shown.
[Table_1]

Answer the following questions about these elements. Each symbol may be used once, more than once or not at all.
Write the symbol of the element which:
(a) forms a stable ion with a 2+ charge ............................................................... [1]
(b) is the least reactive in the period ............................................................... [1]
(c) is used in water treatment ............................................................... [1]
(d) forms an oxide which is the main impurity in iron ore ............................................................... [1]
(e) is an important component of fertilisers ............................................................... [1]
(f) is stored under oil ............................................................... [1]
(g) is used in food containers ............................................................... [1]
(h) is found in the ore zinc blende ............................................................... [1]

Calcium hydroxide, Ca(OH)_2, is slightly soluble in water.
(a) Calcium hydroxide can be made by the reaction of calcium with water.
(i) Write the chemical equation for this reaction.
............................................................................................................. [2]
(ii) Name another substance that reacts with water to form calcium hydroxide.
............................................................................................................. [1]
(b) When calcium hydroxide dissolves in water, it dissociates into ions and forms a weakly alkaline solution.
(i) Suggest the pH of aqueous calcium hydroxide.
............................................................................................................. [1]
(ii) Give the formula of the ion responsible for making the solution alkaline.
............................................................................................................. [1]
(c) Limewater is a saturated solution of calcium hydroxide, Ca(OH)_2(aq).
(i) Name the gas limewater is used to test for.
............................................................................................................. [1]
(ii) Suggest what is meant by the term saturated solution.
.............................................................................................................
............................................................................................................. [2]
(iii) Describe how you would make a sample of limewater starting with solid calcium hydroxide.
.............................................................................................................
.............................................................................................................
............................................................................................................. [2]
(iv) Describe how you would test for the presence of calcium ions in a sample of limewater.
test ........................................................................................................
observations .........................................................................................
............................................................................................................. [3]
(d) A 25.0cm^3 sample of limewater is placed in a conical flask. The concentration of Ca(OH)_2 in the limewater is determined by titration with dilute hydrochloric acid, HCl.
(i) Name the item of apparatus used to measure the volume of acid in this titration.
............................................................................................................. [1]
(ii) State the type of reaction which takes place.
............................................................................................................. [1]
(iii) As well as limewater and dilute hydrochloric acid, state what other type of substance must be added to the conical flask.
............................................................................................................. [1]
(iv) The equation for the reaction is shown.
Ca(OH)_2 + 2HCl → CaCl_2 + 2H_2O
20.0 cm^3 of 0.0500 mol/dm^3 HCl reacts with the 25.0 cm^3 of Ca(OH)_2.
Determine the concentration of Ca(OH)_2 in g/dm^3. Use the following steps.
• Calculate the number of moles in 20.0 cm^3 of 0.0500 mol/dm^3 HCl.
............................... mol
• Determine the number of moles of Ca(OH)_2 in 25.0 cm^3 of the limewater.
............................... mol
• Calculate the concentration of Ca(OH)_2 in mol/dm^3.
............................... mol/dm^3
• Determine the concentration of Ca(OH)_2 in g/dm^3.
............................... g/dm^3 [5]

Transition elements are found in the middle block of the Periodic Table.

(a) Chromium has several isotopes. Manganese has only one isotope.

(i) State what is meant by the term isotopes.
.........................................................................................................................................
......................................................................................................................................... [2]

(ii) State the nucleon number of manganese.
......................................................................................................................................... [1]

(iii) Complete the table to show the number of protons, neutrons and electrons in a $^{52}_{24}Cr^{3+}$ ion.

[Table_1]

[3]

(b) One chemical property of transition elements is that they form coloured compounds.

(i) Give the colours of the following hydrated salts.

• hydrated copper(II) sulfate ................................................................
• hydrated cobalt(II) chloride .................................................................

• conduct electricity
• be hammered into shape.

Fluorine and chlorine are halogens.

(a) Suggest the appearance of fluorine.
............................................................................................................................ [1]

(b) Fluorine reacts with sulfur to form a compound which has 25.2% sulfur by mass and a relative molecular mass of 254.
Determine the molecular formula of this compound.
molecular formula = ................................. [3]

(c) Nitrogen trichloride, $\text{NCl}_3$, is a covalent compound.
Complete the dot-and-cross diagram to show the electron arrangement in a molecule of $\text{NCl}_3$.
Show outer electrons only.
[3]

(d) Lithium chloride, $\text{LiCl}$, is an ionic compound.
Complete the dot-and-cross diagram to show the electron arrangement and charges of the ions in lithium chloride.
[3]

(e) Explain, in terms of attractive forces between particles, why $\text{LiCl}$ is a solid at room temperature but $\text{NCl}_3$ is a liquid with a relatively low boiling point.
...................................................................................................................................
...................................................................................................................................
................................................................................................................................... [3]

(a) Name reaction 1.
......................................................................................................................

(b) Name reaction 2 and write the chemical equation for this reaction.
name .......................................................................................................................
equation ....................................................................................................................

(c) Reaction 3 forms ethanol from alkene A.
(i) Identify alkene A.
......................................................................................................................
(ii) State the type of reaction that occurs during reaction 3.
......................................................................................................................
(iii) State the reagents and conditions needed for reaction 3.
......................................................................................................................

(d) Alkene A is converted into alkane B in reaction 4.
(i) State the reagent and conditions for reaction 4.
......................................................................................................................
(ii) State the general formula of alkanes.
......................................................................................................................

(e) Ethanol is oxidised in reaction 5 by heating it with dilute sulfuric acid and one other reagent.
(i) Identify the other reagent in reaction 5.
......................................................................................................................
(ii) Name the homologous series compound C belongs to.
......................................................................................................................
(iii) Draw the structure of compound C.
Show all of the atoms and all of the bonds.

This question is about polymers.

(a) Polymer X is a condensation polymer.

Part of the structure of polymer X is shown.



(i) How many molecules of water are produced when this part of polymer X is formed from its monomers?
............................................................................................................ [1]

(ii) Complete the structures of the two monomers used to make polymer X.
Show all of the atoms and all of the bonds in the functional groups.


and

[2]

(iii) What type of condensation polymer is X?
............................................................................................................ [1]

(b) Part of polymer Y has the structure shown.



State the number of different types of monomer needed to make polymer Y.
............................................................................................................ [1]

(c) Part of polymer Z has the structure shown.



(i) Draw and name the structure of the monomer which forms polymer Z.
Show all of the atoms and all of the bonds.

name ................................................
[3]

(ii) Name the chemical process used to make the monomer that forms polymer Z.
............................................................................................................ [1]