Question
This question is about iodine and compounds of iodine.
(a) Use the kinetic particle model to describe the separation between the molecules and the type of motion of the molecules in:
- solid iodine
- iodine gas. [4]
(b) The graph shows how the volume of iodine gas changes with pressure. The temperature is kept constant.
Describe how the volume of iodine gas changes with pressure.[1]
(c) (i) Complete the word equation to show the halogen and halide compound which react to form the products iodine and potassium bromide.
(ii) Explain, in terms of the reactivity of the halogens, why aqueous iodine does not react with aqueous potassium chloride
(d) lodine reacts with aqueous sodium thiosulfate, $\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3$.
(i) Balance the chemical equation for this reaction.
$
\mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3+\mathrm{I}_2 \rightarrow \mathrm{Na}_2 \mathrm{~S}_4 \mathrm{O}_6+\ldots . . \mathrm{NaI}
$
(ii) The energy level diagram for this reaction is shown.
Explain how this diagram shows that the reaction is exothermic [1]
(e) Describe a test for iodide ions.
test
observations[2]
(f) Molten sodium iodide is electrolysed.
Predict the product at the positive electrode.[1][Total: 14]
▶️Answer/Explanation
Ans:
(a) solid:
particles touching / particles close together (1)
particles (only) vibrating / not moving from place to place (1)
gas:
particles far apart (1)
particles moving fast / particles moving randomly / particles moving in any direction (1)
4(b) increasing the pressure decreases the volume / decreasing the pressure increases the volume / the higher the volume, the lower
the pressure
4(c)(i) bromine (1)
potassium iodide (1)
Question
This question is about chlorine and compounds of chlorine.
(a) Chlorine is an element in Group VII of the Periodic Table.
State the meaning of the term element.[1]
(b) State one use of chlorine.[1]
(c) Chlorine reacts with phosphorus to produce phosphorus(V) chloride.
(i) Balance the equation for this reaction.
…..P + …..Cl2 → 2PCl5 [2]
(ii) This reaction is exothermic.
State the meaning of the term exothermic.[1]
(d) Chlorine reacts with aqueous sodium bromide.
(i) Complete the word equation for this reaction.
(ii) Describe a test for bromide ions.[2]
test
observations
(iii) When bromine is mixed with aqueous sodium chloride there is no reaction.
Suggest in terms of chemical reactivity why there is no reaction.[1]
(e) A compound of chlorine has the formula C3H6Cl2.
Complete the table to calculate the relative molecular mass of C3H6Cl2.
relative molecular mass = [2] [Total: 12]
Answer/Explanation
Ans:
(a) substance containing only one type of atom / substance where the atoms have the same proton number
(b) water treatment / water purification / killing bacteria
c)(i) 2 (P) (1)
5 (Cl2) (1)
c)(ii) releases thermal energy / releases heat
(d)(i) bromine (1)
sodium chloride (1)
(d)(ii) (add nitric acid and aqueous) silver nitrate (1)
cream precipitate / cream solid (1)
(d)(iii) bromine is less reactive than chlorine / chlorine more reactive than bromine 1
(e) 113 (2)
If two marks not scored, allow 1 mark for H = 6 × 1 / 6 OR Cl = 2 × 35.5 / 71
Question
The table shows the masses of some ions in a 1000cm3 sample of toothpaste.
(a) Answer these questions using only the information in the table.
(i) State which negative ion has the lowest mass in 1000cm3 of toothpaste.[1]
(ii) Name the compound that contains NH4+ and Cl–ions.[1]
(iii) Calculate the mass of phosphate ions in 250cm3 of toothpaste.
mass = g [1]
(b) Describe a test for sulfate ions.[2]
test
observations
(c) Toothpaste also contains cinnamal.
The structure of cinnamal is shown.
Deduce the formula of cinnamal to show the number of atoms of carbon, hydrogen and oxygen.[1]
(d) Cinnamal can be oxidised to a carboxylic acid.
(i) Draw the structure of a carboxylic acid functional group to show all of the atoms and all of the bonds. [1]
(ii) Ethanoic acid is a carboxylic acid.
Ethanoic acid reacts like a typical acid.
Complete the word equation for the reaction of ethanoic acid with sodium carbonate.
[2] [Total: 9]
Answer/Explanation
Ans:
(a)(i) Cl – / chloride
(a)(ii) ammonium chloride
(a)(iii) 6.1 (g)
(b) (acidify and) add barium nitrate (1)
white precipitate (1)
(c) C9H8O
(d)(i)
d)(ii) carbon dioxide (1)
water (1)
Question
(a) Calcium oxide is made by the thermal decomposition of calcium carbonate.
(i) State the meaning of the term thermal decomposition.
(ii) Describe a test for calcium ions.
test ……………………………………………………………………………………………………………………..
observations ………………………………………………………………………………………………………..
(b) Carbon dioxide is produced when dilute hydrochloric acid reacts with calcium carbonate.
\(CaCO_3 + 2HCl → CaCl 2 + CO_2 + H_2O\)
(i) Complete the diagram to show how to measure the volume of carbon dioxide produced during this reaction.
(ii) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate.
● The concentration of hydrochloric acid is decreased.
All other conditions stay the same.
● The temperature is increased.
All other conditions stay the same.
(c) Carbon dioxide is also formed when the hydrocarbon \(C_3H_8\) is completely combusted.
(i) State the meaning of the term hydrocarbon.
(ii) The hydrocarbon \(C_3H_8\) is called propane.
Name the homologous series that propane belongs to.
(iii) Name two substances formed by the incomplete combustion of propane.
………………………………………………………. and ………………………………………………………
Answer/Explanation
Answer:
(a) (i) breakdown of substance / idea of one substance forming two or more substances (1)
using heat / on heating (1)
(ii) add (aqueous) sodium hydroxide (1)
white precipitate / white solid (1)
OR
add (aqueous) ammonia (1)
no precipitate / very slight white precipitate (1)
(b) (i) gas syringe / upturned measuring cylinder dipping into container (1)
apparatus is workable and airtight (1)
(ii) lower concentration of acid: decreases (in rate) / reaction slower / lower rate / slows down (1)
higher temperature: increases (in rate) / reaction faster / higher rate / speeds up (1)
(c) (i) compound containing hydrogen and carbon only / compound containing hydrogen and carbon and no other substance (2)
if two marks not scored, 1 mark for:
compound containing hydrogen and carbon / it contains hydrogen and carbon only
(ii) alkane(s)
(iii) 1 mark each for any 2 of:
• carbon monoxide
• carbon
• water
Question
The table shows the mass of some of the ions in a 1000 \(cm^3\) sample of sea water.
(a) Answer these questions using only the information in the table.
(i) State which negative ion has the lowest mass in 1000 \(cm^3\) of sea water.
(ii) Give the formulae of the ions in potassium sulfate.
………………………………………………………. and ………………………………………………………
(iii) Calculate the mass of calcium ions in 200cm3
of this sample of sea water.
mass = ………………………… mg
(iv) A sample of this sea water is evaporated.
State the name of the compound which is present in the greatest quantity when this sample is evaporated.
(v) Give the name of the ion which reacts with aqueous silver nitrate to give a cream precipitate.
(b) The \(B_3O_6^{3–}\) ion can be converted to boric acid, \(H_3BO_3\).
Boric acid is also produced when boron trichloride, \(BCl_3\), reacts with water.
Complete the equation for this reaction.
\(BCl_3 + …..H_2O → H_3BO_3 + …..HCl\)
(c) The symbol of a strontium ion is shown.
\(^{87}_{38} Sr^{2+}\)
Deduce the number of electrons, protons and neutrons in one atom of this strontium ion.
number of electrons …………………………………………………………………………………………………….
number of protons ………………………………………………………………………………………………………
number of neutrons …………………………………………………………………………………………………….
(d) Some isotopes of strontium are radioactive.
(i) Give one medical use of radioactive isotopes.
(ii) The isotope \(^{235}\)U is also radioactive.
State the major use of this isotope of uranium.
Answer/Explanation
Answer:
(a) (i) \(B_3O_6^{3-}\) / metaborate
(ii) \(K^+\) AND \(SO_4^{2-}\)
(iii) 80 (mg)
(iv) sodium chloride
(v) bromide
(b) \(3(H_2O)\)
3(HCl)
(c) number of electrons: 36 (1)
number of protons: 38 (1)
number of neutrons: 49 (1)
(d) (i) cancer treatment / tracer (e.g. for thyroid function)
(ii) source of energy / energy production