Atomic combinations: Grade 11 Past Paper Questions

1.5 Which ONE of the following molecules is non-polar, but has polar bonds? A. H₂O B. HCl

QUESTION 2. 2.1 Write down the number of valence electrons in an atom of: 2.1.1 fluorine 2.1.2 hydrogen. 2.2 Define a covalent bond. 2.3 Write down the name given to the type of bond between the particles in: 2.3.1 NaF 2.3.2 CH₄. 2.4 Write down the Lewis structure for: 2.4.1 F₂ 2.4.2 HCN 2.4.3 MgF₂. 2.5 State whether the following molecules are POLAR or NON-POLAR and write down their shape: 2.5.1 H₂O 2.5.2 CH₄ 2.5.3 NH₃. 2.6 Both BF₃ and NH₃ are molecules that are made up of four atoms. Explain the difference in shapes between these molecules. 2.7 Use Lewis diagrams to show how a dative covalent bond forms between H₂O and the H⁺ ion.

QUESTION 3. The graph below shows the relationship between the potential energy and the distance between the nuclei of the atoms in the H₂ molecule. 3.1 Define the term bond energy. 3.2 Give a reason why two hydrogen atoms: 3.2.1 Attract each other 3.2.2 Repel each other. 3.3 Write down the: 3.3.1 Bond energy of H₂ 3.3.2 Bond length of H₂. 3.4 The BOND LENGTH of H₂ is less than that of N₂. Give a reason for this statement. 3.5 The BOND ENERGY of H₂ is less than that of N₂. Give a reason for this statement. 3.6 Explain the shape of the graph between 0 and 75 pm.

QUESTION 1: MULTIPLE-CHOICE QUESTIONS. 1.1 The hydrogen bond is a type of... A. ionic bond. B. metallic bond. C. covalent bond. D. intermolecular force. 1.2 Which ONE of the following substances has dative covalent bonds? C. H₃O⁺ D. NH₄⁺. 1.3 Which ONE of the following liquids will have the greatest vapour pressure when equal amounts are placed in a sealed container at the same temperature? A. HF B. HCl C. HBr D. HI. 1.4 Which ONE of the following statements is correct about intermolecular forces? A. They hold atoms together in a molecule. B. They are much stronger than intramolecular forces. C. They determine the physical state of the compound. D. They are chemical bonds.

2.7 Use Lewis diagrams to show how a dative covalent bond forms between H₂O and the H⁺ ion. QUESTION 3. The graph below shows the relationship between the potential energy and the distance between the nuclei of the atoms in the H₂ molecule. 3.1 Define the term bond energy. 3.2 Give a reason why two hydrogen atoms: 3.2.1 Attract each other 3.2.2 Repel each other. 3.3 Write down the: 3.3.1 Bond energy of H₂ 3.3.2 Bond length of H₂. 3.4 The BOND LENGTH of H₂ is less than that of N₂. Give a reason for this statement. 3.5 The BOND ENERGY of H₂ is less than that of N₂. Give a reason for this statement. 3.6 Explain the shape of the graph between 0 and 75 pm.

A multiple-choice section (5 items). Then in Question 2: define a covalent bond, a molecule, and a lone pair; state the number of lone pairs and bonds shown in given structures; identify the type of bond (covalent) in given structures; name two molecules that contain lone pairs (H₂O and NH₃); and use dative covalent bonding to explain how the hydronium ion (H₃O⁺) and the ammonium ion (NH₄⁺) form.

Continuing Question 2: define electronegativity, calculate an electronegativity difference for the C–O bond, and explain why carbon monoxide is polar while carbon dioxide is non-polar based on their molecular shapes. Then Question 3: define bond order, give the bond order of a named molecule, state how bond order relates to bond length and to bond energy, and calculate the energy needed to break a given set of bonds.