Y12 2018

Which of the following contains the most chloride ions?

• 15 cm³ of 3.40 × 10⁻² mol dm⁻³ aluminium chloride solution

• 30 cm³ of 5.50 × 10⁻² mol dm⁻³ calcium chloride solution

• 40 cm3 of 2.30 × 10−2 mol dm−3 hydrochloric acid

• 45 cm³ of 2.20 × 10⁻² mol dm⁻³ sodium chloride solution

The maximum uncertainty when weighing 0.250 g on a balance was 0.001 g.

What is the percentage uncertainty?

• 4.0%

• 0.4%

• 0.8%

• 250%

Bromine exists as two isotopes ⁷⁹Br and ⁸¹Br, which are found in almost equal abundance.

Which of the statements is correct?

• The first ionisation energy of ⁷⁹Br is less than the first ionisation energy of ⁸¹Br

• The atomic radius of ⁷⁹Br is less than the atomic radius of ⁸¹Br

• The mass spectrum of C₃H₇Br has two molecular ion peaks at 122 and 124

• ⁷⁹Br is more reactive than ⁸¹Br

The equation for the hydrogenation of ethyne is

C₂H₂ + 2H₂ ⟶ C₂H₆

The experimental yield is 65.0%.

What is the mass in grams of ethane that can be produced from 16.20 g of hydrogen?

• 42.53 g

• 78.98 g

• 121.5 g

• 527.7 g

What is the number of atoms in 0.0100 mol of NH₃?

(The Avogadro constant L = 6.022 × 10²³mol^-1)

• 6.02 × 10²⁵

• 1.20 × 10²³

• 1.81 × 10²²

• 2.41 × 10²²

What is the empirical formula of 4-hydroxypent-2-ene?

• C₅H₁₂O

• C₅H₁₀O

• CH₂O

• C₅H₉OH

Which is the correct classification for the element yttrium (Y)?

• s block

• p block

• d block

• f block

2.40 g of an explosive, J, contains 0.473 g of nitrogen. J also contains 33.8% carbon and 1.41% hydrogen by mass. The remainder of J is oxygen.

What is the empirical formula of J?

• C₄HNO₂

• CH₂N₂O

• C₂HNO₂

• CHNO

After reaction of some zinc metal with excess sulfuric acid, a student collected 40.8 g of ZnSO₄.7H₂O crystals. The yield of crystals was 70.0%.

What was the original mass of zinc used?

• 9.28 g

• 13.3 g

• 23.6 g

• 58.3 g

Which of the following is a correct statement about the trend in atomic radius across Period 3 of the Periodic Table?

• radius increases because the atoms have more electrons

• radius decreases because nuclear charge increases

• radius increases because shielding (screening) increases

• radius decreases because shielding (screening) decreases