O level Chemistry Chemical Bonding

When magnesium reacts with oxygen to form magnesium oxide, which of the following is not true?

• A magnesium atom loses two electrons

• An oxygen atom gains one electron

• Forces of attraction between ion of magnesium and oxygen are strong

• The chemical formula of the compound is MgO

Which compound contains both ionic and covalent bonds?

• ammonia

• ethyl ethanoate

• potassium nitrate

• sodium chloride

The experiment shown is used to test the electrical conductivity of potassium iodide crystals. However the lamp does not light up. Distilled water is added to the beaker and the lamp lights up. Why is this so?

• Metal ions are free to move when potassium iodide melts

• Metal ions are free to move when potassium reacts with water

• Electrons are free to move in the solution when potassium iodide dissolves

• Oppositely charged ions are free to move in the solution when potassium iodide dissolves

The dot-cross diagram (with only the outer electrons) of the compound formed between element X and Z is shown. Which of the following is the correct set of formula of the chloride of X and X?

• XCl, Z₃Cl

• XCl, ZCl₃

• XCl₂, Z₃Cl

• XCl₂, ZCl₃

Metals have positive ions in a 'sea of electrons'. Which metal atom contributes the least number of electrons to this 'sea of electrons'?

• Aluminum

• Magnesium

• Sodium

• Zinc

The properties of the chlorides of Period III elements shows that the boiling points of sodium chloride and silicon tetrachloride are 1465°C and 57°C respectively. What is the reason behind the difference in boiling points?

• covalent bonds being weaker than ionic bonds

• sodium chloride having strong metallic bonds

• silicon tetrachloride having weak intermolecular forces of attraction

• silicon forming weaker bonds with chlorine than does sodium

Which compound cannot have this arrangement of its ions?

• lithium nitrate

• zinc sulfate

• sodium oxide

• lead(II) sulfate

When sucrose is heated, it melts at 192°C. At this temperature it starts to decompose, and the liquid sucrose turns dark brown. Which conclusion is correct?

• the covalent bonds are stronger than the intermolecular forces

• the intermolecular forces, and some covalent bonds are about the same strength

• the intermolecular forces are stronger than the covalent bonds

• the structure of the solid is a lattice structure

Which of the following correctly shows the type of bonds and chemical formula of the compound formed between X and Y?

• covalent bond, XY₂

• ionic bond, XY

• ionic bond, X₂Y₃

• covalent bond X₃Y₂

Which of the following statements concerning molecules is not correct

• A molecule can be attracted to another separate molecule with intermolecular forces

• A molecule always contains two or more atoms from different elements

• The atoms in a molecule achieve stable valence electron configurations by sharing of electrons

• Molecules by themselves do not conduct electricity