Chemistry

Question 1

Describe the structure of an atom.

Answer 1

An atom has a small central nucleus containing protons and neutrons. Electrons orbit the nucleus in energy levels.

Question 2

Why do group I metals become more reactive as you go down the group?

Answer 2

As you go down group I, atoms have more electron shells. The outer electrons are further from the nucleus and more easily lost, increasing reactivity.

Question 3

Explain why sodium chloride has a high melting point.

Answer 3

Sodium chloride has strong electrostatic forces of attraction between oppositely charged ions. A lot of energy is needed to overcome these bonds, resulting in a high melting point.

Question 4

Describe the properties of giant covalent structures.

Answer 4

Diamond has strong covalent bonds in all directions, making it very hard and giving it a very high melting point.

Question 5

Calculate the relative formula mass (Mr) of a compound.

Answer 5

Add up the relative atomic masses of the atoms shown in the formula.

Question 6

Calculate the percentage of an element in a compound.

Answer 6

Use the formula: (Mass of element ÷ Mr of compound) × 100.

Question 7

Describe how you would make pure copper sulfate crystals from copper oxide.

Answer 7

1. Add copper oxide a little at a time while stirring until no more dissolves. 2. Filter the mixture to remove excess copper oxide. 3. Heat the filtrate gently to evaporate water. 4. Leave the solution to cool and form crystals. 5. Dry the formed copper sulfate crystals.

Question 8

Identify which metal is displaced in a displacement reaction.

Answer 8

The more reactive metal displaces the less reactive metal from its compound.

Question 9

Explain what happens during the electrolysis of molten lead bromide.

Answer 9

Lead ions move to the cathode and gain electrons to form lead metal. Bromide ions move to the anode and lose electrons to form bromine gas.

Question 10

Is bond making exothermic or endothermic? Explain.

Answer 10

Bond making is exothermic because it releases energy to the surroundings.

Question 11

Sketch and label a reaction profile for an exothermic reaction.

Answer 11

Draw reactants higher than products, with the activation energy as a peak. Indicate the overall energy release by an arrow from reactants to products.