0620 Foundations
What is the state of matter in which particles are closely packed but can slide past each other?
Liquid
What is the volume of 1 mole of gas at room temperature and pressure?
24 dm3
What type of reaction occurs when an acid reacts with a base?
Neutralisation
What ion is present in all acidic solutions?
H⁺ (hydrogen ion)
What is the name of the process used to break large hydrocarbons into smaller ones?
Catalytic Cracking
What is an isotope?
Atoms of the same element with the same number of protons but different numbers of neutrons.
Calculate the number of moles in 10 g of CaCO₃.
moles = 10 ÷ 100 = 0.10 mol
What is the definition of Activation Energy?
The minimum energy required for colliding particles to react/for collisions between reactants to be successful.
What happens to reactivity down Group 1? Why?
Reactivity increases
More shells, less electrostatic attraction, easier to lose electrons (react)
What is formed when ethanol is oxidised?
Ethanoic acid
Explain why isotopes have identical chemical properties.
They have the same number of electrons and the same electron arrangement.
4 g of hydrogen reacts with excess oxygen.
What is the mass of water produced?
2H₂ + O₂ → 2H₂O
Ar H=1
Mr H₂ = 2
Moles H₂ = 4 ÷ 2 = 2 mol
From ratio → 2 mol H₂ makes 2 mol H₂O
Mr H₂O = 18
Mass = 2 × 18 = 36 g
What is reduced in this reaction?
CuO + H₂ → Cu + H₂O
Copper(II) oxide (CuO)
What happens when chlorine reacts with potassium bromide solution?
Chlorine displaces the bromide ion to form bromine.
Solution turns orange/brown
Write the balanced equation for complete combustion of decane.
2C10H22 + 31O2 --> 20CO2 + 22H2O
Sodium chloride has a melting point of 801 degree C and silicon dioxide has a melting point of 1725 degree C.
a) State the type of bonding in sodium chloride.
b) State the type of bonding in silicon dioxide.
c) Explain why sodium chloride conducts electricity when molten but silicon dioxide does not.
d) Explain why both have high melting points.
a) Ionic bonding
b) Giant covalent bonding
c) Molten sodium chloride has mobile ions; silicon dioxide has no free charged particles.
d) Both have strong forces throughout a giant structure requiring large energy to overcome.
25 cm³ of 2 mol/dm³ HCl reacts with NaOH.
Calculate moles of HCl used.
Convert volume:
25 cm³ = 0.025 dm³
Moles = concentration × volume
= 2 × 0.025
= 0.05 mol
The enthalpy change for the reaction is:
CH₄ + 2O₂ → CO₂ + 2H₂O
ΔH = –890 kJ/mol
Bond energies (kJ/mol):
O=O = 498
C=O = 805
O–H = 463
C–H = x
Calculate the bond energy of the C–H bond.
Step 1: Bonds broken
CH₄ → 4(C–H) = 4x
2O₂ → 2 × 498 = 996
Total broken = 4x + 996
Step 2: Bonds formed
CO₂ → 2 × 805 = 1610
2H₂O → 4 × 463 = 1852
Total formed = 1610 + 1852 = 3462
Step 3: Apply formula
ΔH = broken – formed
–890 = (4x + 996) – 3462
–890 = 4x – 2466
4x = 1576
x = 394 kJ/mol
Describe how to prepare a pure sample of copper(II) sulfate crystals from copper(II) oxide and sulfuric acid.
Add excess copper oxide, filter, evaporate filtrate (copper (II) sulfate solution), allow to crystallise by heating until half volume of solution, allow to cool and then dry the crystals.
Ethene forms poly(ethene).
a) Explain what happens to the C=C bond.
b) Draw the repeating unit.
c) Explain why poly(ethene) is chemically unreactive.
d) Explain why it causes environmental problems.
a) Double bond breaks and forms single bonds linking monomers.
b) –CH₂–CH₂–
c) Only strong C–C and C–H bonds present.
d) It is non-biodegradable.
Explain:
a) Why aluminium is extracted by electrolysis but iron is extracted by reduction with carbon.
b) Why copper can sometimes be found unreacted in nature.
c) Why potassium cannot be extracted using carbon.
a) Aluminium is above carbon in the reactivity series; carbon cannot reduce it.
Iron is below carbon; carbon can reduce iron oxide.
b) Copper is very unreactive and does not easily form compounds.
c) Potassium is too reactive; carbon cannot reduce potassium oxide.
Magnesium reacts with hydrochloric acid.
Mg + 2HCl → MgCl₂ + H₂
5 g of Mg reacts with 10 g of HCl.
(Ar: Mg=24, H=1, Cl=35.5)
a) Calculate moles of Mg.
b) Calculate moles of HCl.
c) Identify the limiting reagent.
d) Calculate the mass of H₂ produced.
Mr HCl = 36.5
a) moles Mg = 5 ÷ 24 = 0.208 mol
b) moles HCl = 10 ÷ 36.5 = 0.274 mol
c) Ratio requires 1 Mg : 2 HCl
0.208 mol Mg would need 0.416 mol HCl
Only 0.274 mol available → HCl is limiting reagent
d) From equation:
2 HCl → 1 H₂
0.274 mol HCl produces
0.274 ÷ 2 = 0.137 mol H₂
Mr H₂ = 2
Mass = 0.137 × 2 = 0.274 g
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
ΔH = –92 kJ/mol
a) Explain what happens to the position of equilibrium if temperature increases.
b) State what happens to the yield of ammonia.
c) Explain what happens to the rate of reaction.
d) What happens to the equilibrium iron is added?
a) Increasing temperature favours the endothermic direction.
Forward reaction is exothermic, so equilibrium shifts left.
b) Yield of ammonia decreases.
c) Rate of both forward and backward reactions increases because particles have more kinetic energy.
d) Stays the same, catalysts do not affect equilibrium positions, just rate at which equilibrium is achieved.
A strip of magnesium is placed into iron(II) sulfate solution.
a) Predict whether a reaction occurs.
b) Write the balanced equation.
c) Identify what is oxidised and reduced.
d) State one observation.
a) Yes, magnesium is more reactive than iron.
b) Mg + FeSO₄ → MgSO₄ + Fe
c) Magnesium is oxidised.
Iron(II) ions are reduced.
d) Grey iron solid forms; solution becomes colourless.
Ethanol reacts with ethanoic acid.
a) Name the type of reaction.
b) Write the equation and write out the displayed formulas of all of reactants and products.
c) Name the product.
a) Esterification (condensation reaction)
b)
CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O
c) Ethyl ethanoate