AS Chem Review

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Oxygen has three stable isotopes, ¹⁶O, ¹⁷O and ¹⁸O. All three isotopes are present in a sample of oxygen gas, O₂, which was analysed using a mass spectrometer.

How many peaks associated with the O²⁺ ion would be expected?

• 3

• 5

• 6

• 9

• MgCl₂

• CaBr₂

• Na₂S

• K₂Se

A σ bond is made between two carbon atoms in a molecule of ethene.

Which diagram shows the orbital overlap that occurs to form this bond?

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X, Y and Z are all gases that behave ideally and react according to the equation shown.

X(g) + 2Y(g) → 2Z(g)

When 3.0 mol of X and 3.0 mol of Y are placed inside a container with a volume of 1.0 dm³, they react to form the maximum amount of Z.

The final temperature of the reaction vessel is 120 °C.

What is the final pressure inside the reaction vessel?

• 4.49 × 10⁶Pa

• 9.80 × 10⁶Pa

• 1.47 × 10⁷Pa

• 1.96 × 10⁷Pa

Which pair of substances are both simple molecular?

• C₆₀ and graphene

• C₆₀ and iodine

• graphene and graphite

• graphite and iodine

X is either chlorine or an oxide of chlorine.

X reacts with water, under suitable conditions, to form the two acids HCl and HClO₃ in the mole ratio of 1 (HCl ) : 5 (HClO₃).

What could be X?

• Cl₂

• Cl₂O

• ClO₂

• Cl₂O₇

Ethyl ethanoate undergoes the following reaction.

CH₃CO₂C₂H₅ + H₂O = C₂H₅OH + CH₃CO₂H K_c = 0.27

Equal amounts of ethanoic acid and ethanol were mixed together and allowed to reach equilibrium.

At equilibrium, the concentrations of both ethanoic acid and ethanol were 0.42 mol dm^–3.

What is the concentration of ethyl ethanoate at equilibrium?

• 0.22 mol dm^–3

• 0.65 mol dm^–3

• 0.81 mol dm^–3

• 1.54 mol dm^–3

A white solid, Z, is soluble in water. A sample of Z is heated with a Bunsen burner until there is no further change. When the residue is shaken with water a solution is formed with no solid remaining.

What could Z be?

• MgCO₃

• Mg(NO₃)₂

• BaCO₃

• Ba(NO₃)₂

Which series shows molecules in order of increasing bond angle?

• CH₄ → BF₃ → NH₃

• H₂O → CO₂ → BF₃

• NH₃ → CH₄ → CO₂

• NH₃ → CH₄ → H₂O