Question
This question is about the first 30 elements in the Periodic Table.
Name the element which:
(a) is 78% of clean, dry air [1]
(b) has atoms with an electronic structure of 2,8,1 [1]
(c) is extracted from hematite [1]
(d) forms an oxide with a giant covalent structure [1]
(e) is the gas with the slowest rate of diffusion at room temperature[1]
(f) has an anhydrous chloride which turns pink when water is added[1]
(g) has aqueous ions which form a white precipitate when added to aqueous silver ions[1]
(h) forms a blue hydroxide which dissolves in aqueous ammonia[1]
(i) is added to molten iron to remove impurities in the steel making process[1]
(j) is used to galvanize iron. [1] [Total: 10]
Answer/Explanation
Ans:
1(a) nitrogen
1(b) sodium
1(c) iron
1(d) silicon
1(e) chlorine
1(f) cobalt
1(g) chlorine
1(h) copper
1(i) oxygen
1(j) zinc
Question
Period 3 contains the elements sodium to argon. This question asks about the chemistry of each of the Period 3 elements or their compounds.
(a) Sodium nitrate is a white crystalline solid. When heated it melts and the following reaction occurs.
\(2NaNO_3(l) → 2NaNO_2(l) + O_2\)(g)
A 3.40g sample of sodium nitrate is heated. Calculate the
• number of moles of \(NaNO_3\) used, ……………………………. mol
• number of moles of \(O_2\) formed, ……………………………. mol
• volume of \(O_2\) formed, in \(dm^{3}\) (measured at r.t.p.). …………………………….\( dm^{3}\)
[3]
(b) Magnesium reacts slowly with warm water to form a base, magnesium hydroxide.
(i) Explain what is meant by the term base.
……………………………………………………………………………………………………………………… [1]
(ii) Write a chemical equation for the reaction between magnesium and warm water.
……………………………………………………………………………………………………………………… [2]
(c) Aluminium oxide is amphoteric. It is insoluble in water. Describe experiments to show that aluminium oxide is amphoteric.
…………………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………. [3]
(d) Silicon(IV) oxide has a giant structure.
(i) Name the type of bonding in silicon(IV) oxide.
……………………………………………………………………………………………………………………… [1]
(ii) Give two physical properties of silicon(IV) oxide.
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………… [2]
(e) Calcium phosphate is used in fertilisers. The bonding in calcium phosphate is ionic. Calcium phosphate contains the phosphate ion, \(PO_4\)\
(i) What is ionic bonding?
…………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… [2]
(ii) Deduce the formula of calcium phosphate. ……………………………………………………………………………………………………………………… [1]
(f) Sulfur tetrafluoride, \(SF_4\), can be made by combining gaseous sulfur with fluorine.
\(S(g) + 2F_2(g) → SF_4(g)\)
The reaction is exothermic.
(i) Complete the energy level diagram for this reaction. Include an arrow which clearly shows the energy change during the reaction.
(ii) During the reaction the amount of energy given out is 780kJ/mol.
The F–F bond energy is 160kJ/mol.
Use this information to determine the bond energy, in kJ /mol, of one S–F bond in \(SF_4\).
……………………………. kJ/mol [3]
(g) Chlorine and compounds of chlorine are important in water treatment and in laboratory testing for water.
(i) Chlorine is added to water to make the water safe to drink.
Explain why adding chlorine makes water safe to drink.
……………………………………………………………………………………………………………………… [1]
(ii) A compound of chlorine is used in the laboratory to test for the presence of water.
Name the compound of chlorine used in this test and describe the colour change seen in a positive result of this test.
name of compound ……………………………………………………………………………………………….
colour change from …………………………………………… to ……………………………………………
[3]
(h) Argon is an unreactive noble gas.
(i) Explain why argon is unreactive.
……………………………………………………………………………………………………………………… [1]
(ii) Give one use of argon.
……………………………………………………………………………………………………………………… [1] [Total:27]
Answer/Explanation
2(a)
number of moles of \(NaNO_3\) used: 3.40/85 = 0.04(00) (mol)
OR
\(4.(00)× 10^–2 \)(mol);
number of moles of O2 formed: 0.04/2 = 0.02(00) (mol)
OR
\(2.(00)× 10^–2\) (mol);
volume of\( O_2\) formed: 0.02× 24 = 0.48\( (dm^3)\);
2(b)(i) (a substance which is) a proton/H+ /hydrogen ion acceptor; 1
2(b)(ii) \(Mg(s) + 2H_2O(l) → Mg(OH)_2(aq) + H_2(g)\)
\(Mg(OH)_2\); rest of equation;
2(c)
M1 add a named acid, e.g. HCl and a named alkali, e.g. NaOH;
M2 \(Al_2O_3\) will react with/neutralises both reagents;
M3 and so it will dissolve into the reagent/form a solution;
2(d)(i) covalent;
2(d)(ii) any 2 from: high melting point/high boiling point;
poor conductor (of electricity); hard; insoluble;
2(e)(i)
M1 (electrostatic) attraction;
M2 between oppositely charged ions;
2(e)(ii) \(Ca_3(PO_4)_2\);
2(f)(i)
M1 exothermic mark: horizontal product energy line at lower energy than that of reactant energy line;
M2 label of product mark: \(SF_4\);
M3 correct direction of vertical heat of reaction arrow: arrow must start level with reactant energy and finish level with product energy and must have only one (correct) arrow-head;
2(f)(ii)
M1 bond energy of \(2F_2: 2 × F–F = 2 × 160 = 320 (kJ/mol)\);
M2 bond energy of all bonds in SF4: 780 + 320 = 1100 (kJ/mol);
M3 calculated bond energy of \(SF_4\) divided by 4: 1100/4 = 275 (kJ/mol);
2(g)(i) kills bacteria;
2(g)(ii) name of compound: cobalt(II) chloride;
from: blue;
to: pink;
2(h)(i) it has a complete outer shell/a full outer shell/8 electrons in the outer shell; 1
2(h)(ii) (in) lamps;
Question
The table gives some information about five substances.
(a) Which substance in the table has ionic bonding? ……………………………………………………………………………………………………………………………. [1]
(b) Which substance in the table has a giant covalent structure? ……………………………………………………………………………………………………………………………. [1]
(c) Name a method you could use to separate a mixture of substance J and water. ……………………………………………………………………………………………………………………………. [1]
(d) Name a method you could use to obtain substance F from a mixture of substance F and water.
(e) Describe how you could obtain a solid sample of substance H from a mixture of substance H and substance
(f) Substance J is a metal. Describe how substance J is able to conduct electricity when it is a solid.
▶️Answer/Explanation
Ans:
1(a) H
1(b) G
1(c) filtration
1(d) fractional
distillation
1(e) add / mix / stir/ dissolve / shake /heat with water
filter/decant
heat (filtrate) or (leave filtrate to) evaporate
1(f) electrons
(electrons) move / flow (throughout structure)
Question
(a) Nickel is extracted from nickel(II) oxide, NiO, by heating with carbon.
Complete the symbol equation for this reaction.
…..NiO + C → 2Ni + ……………
(b) Nickel is refined by electrolysis.
(i) Complete the boxes to label the diagram below to show
• the negative electrode (cathode),
• the positive electrode (anode),
• the electrolyte.
(ii) At which electrode is the pure nickel formed?
(c) Molten nickel(II) chloride can be electrolysed using graphite electrodes.
(i) Predict the products of this electrolysis at
the positive electrode (anode), ……………………………………………………………………………….
the negative electrode (cathode). ……………………………………………………………………………
(ii) Give two reasons why graphite is used for electrodes.
1. ………………………………………………………………………………………………………………………..
2. ………………………………………………………………………………………………………………………..
(d) The structures of diamond and graphite are shown below.
(i) Explain how the structure of diamond relates to its use in cutting hard materials.
(ii) Explain how the structure of graphite relates to its use as a lubricant.
Answer/Explanation
Answer:
(a) 2 (Ni);
\(CO_2\) (on right);
(b) (i) positive electrode/ anode in box on left;
negative electrode/ cathode in upper box on right;
electrolyte/named suitable electrolyte in lower box on right;
3 correct = [2]
1 or 2 correct = [1]
(ii) cathode/ negative electrode;
(c) (i) the positive electrode: chlorine;
the negative electrode: nickel;
(ii) inert/ unreactive;
conducts electricity;
(d) (i) giant structure/ lots of carbon atoms joined to each other/ lattice of covalent bonds;
strong (covalent) bonds throughout;
(ii) weak forces between layers;
layers can slide (over each other);