CHEMISTRY CONTEST SENIOR CLASSES JUNE 2024

0.0625 moles of methane is burnt in air according to the following equation:

CH₄ + 2O₂ → CO₂ + 2H₂O

How many moles of Oxygen are required for this combustion reaction?

• 0.03125

• 0.0625

• 0.125

• 0.25

Assuming that all the chemicals involved in the reaction are in the gaseous state, the balanced symbol equation is:

CH₄ + 2O₂ → CO₂ + 2H₂O

What is the total volume of the gas produced when 2500 cm³ of methane is burned?

• 2500 cm³

• 5000 cm³

• 7500 cm³

• 1000 cm³

Which of the following is a mixture?

• Salt

• Air

• Water

• Ammonia

Which one of the following pairs of atoms is most likely to form an ionic bond?

• Na and F

• C and F

• N and F

• O and F

Which of the following statement is incorrect?

• the greater the number of electrons in a molecule, the greater the van der Waals forces

• the layers in graphite are held together by Van der Waals forces

• the boiling point of noble gases increases down the group

• Water has a higher than expected boiling point because of intermolecular hydrogen bond

Which one of the following statements about negative ions is incorrect?

• they are also known as anions

• they are formed when atoms gain electrons

• they are larger than the atom from which they were formed

• they are smaller than the atom from which they were formed.

Which of the following phrases would be used in a description for bonding in BOTH metals and ionic salts:

• Strong electrostatic attractions

• Ions

• Giant Lattice

• Delocalized electrons

Which of the following best describes the correct order of oxygen, fluorine, and nitrogen's atomic radii?

• O < F < N

• N < F < O

• F < O < N

• O < N < F

A solution of sulphuric (VI) acid, H₂SO₄, contain 9.8 g of the acid in 250 cm³ of solution.

What is the concentration in mol/dm³?

Relative atomic masses H = 1, S = 32, O = 16

• 0.10 mol/dm³

• 0.20 mol/dm³

• 0.40 mol/dm³

• 0.80 mol/dm³

The chemical equation for the preparation of lead (II) sulphate is written below.

Pb(NO₃)₂ (_ _ _) + Na₂SO₄ (_ _ _) → PbSO₄ (_ _ _) + 2NaNO₃ (_ _ _)

What are the state symbol for each substances in this reaction?

• aq, aq, s, aq

• aq, aq, s, s

• s, aq, aq, s

• s, aq, aq, s, aq