1st Semester Assessment

Which of these substances is a molecule?

• Magnesium

• Bromine gas

• Sodium chloride

The table 1 below shows the number of protons and neutrons of three atoms, X, Y and Z.

Atoms X , Y and Z are

• Ions

• Isomers

• Isotopes

Which of the following electron arrangements has three valence electrons?

• 
• 
• 

Which of the following statements is true about the symbols of X and Y in Diagram 1?

• X and Y have same chemical properties

• X and Y have 6 valence electrons each

• X and Y have same physical properties

Which of the following shows the electron arrangement and the number of neutrons in magnesium atom in Diagram 2?

• 2.8.2 / 24

• 2.8.2 / 12

• 2.8 / 12

When magnesium burns in excess oxygen gas, a white powder magnesium oxide, MgO is formed.

Which of the following is a balanced chemical equation to represent the reaction?

• Mg(s) + O(g) → MgO(s)

• Mg(s) + O₂(g) → MgO(s) + O(g)

• 2Mg(s) + O₂(g) → 2MgO(s)

The following equation represents the reaction of metal M with an acid.

M + 2HCl --> MCl₂ + H₂

What is the volume of hydrogen gas produced when 150 cm³ of 0.2 mol dm^-3 hydrochloric acid is used?

[1 mol of gas occupies the volume of 24 dm³ at room temperature and pressure]

• 0.36 cm³

• 0.72 cm³

• 360.00 cm³

• 720.00 cm³

Diagram 3 shows the set-up of apparatus to determine the empirical formula of an oxide of metal X.

Which of the following is metal X?

• Zinc

• Copper

• Tin

Sodium reacts with chlorine to form sodium chloride.

Which of the following equation represents this reaction?

• Na + Cl₂ --> NaCl₂

• Na + Cl --> NaCl

• 2Na + Cl₂ --> 2NaCl

Which of the following is the correct chemical formula for aluminium sulphate?

• Al₃(SO₄)₂

• Al₂(SO4)₃

• AlSO₄