Here are the solutions to your chemistry questions, kamogelo. 1. What percentage of the air is oxygen? Approximately 21% of the air is oxygen. 2. Give the atomic numbers of oxygen, iron and magnesium? • Oxygen (O): 8 • Iron (Fe): 26 • Magnesium (Mg): 12 3. Give the meanings of the following terms: a) combustion Combustion is a rapid chemical reaction between a substance and an oxidant, usually oxygen, that produces heat and light. It is commonly known as burning. b) corrosion Corrosion is the gradual destruction of materials, usually metals, by chemical reaction with their environment. A common example is the rusting of iron. 4. Write a general word equation to represent a metal reacting with oxygen. $$ \text{Metal} + \text{Oxygen} \rightarrow \text{Metal oxide} $$ 5. State four safety points to consider when using a Bunsen burner. • Ensure the work area is clear of flammable materials. • Check that the rubber tubing is securely attached and free from cracks. • Always light the burner with a match or striker before turning on the gas fully. • Never leave a lit Bunsen burner unattended. 6. Steel wool (iron) reacts with oxygen. a) Describe the reactants. The reactants are iron (in the form of steel wool), which is a grey, solid metal, and oxygen, which is a colorless, odorless gas present in the air. b) What do you observe when the reaction takes place? When steel wool reacts with oxygen, it glows brightly, sparks, and changes color to a dark, reddish-brown. c) Describe the product of the reaction. The product is iron oxide (rust), which is a brittle, reddish-brown solid. d) Write a balanced chemical equation for the reaction. $$ 4\text{Fe(s)} + 3\text{O}_2\text{(g)} \rightarrow 2\text{Fe}_2\text{O}_3\text{(s)} $$ e) Draw a diagram of the balanced chemical equation, using circles to represent the atoms and molecules. A diagram would show: • Four individual circles representing iron atoms (Fe). • Three pairs of circles joined together representing oxygen molecules ($\text{O}_2$). • An arrow pointing to two structures, each consisting of two iron circles bonded to three oxygen circles, representing iron oxide molecules ($\text{Fe}_2\text{O}_3$). 7. Magnesium reacts with oxygen. a) Describe the reactants. The reactants are magnesium, which is a silvery-white, solid metal ribbon, and oxygen, which is a colorless, odorless gas. b) What do you observe when the reaction takes place? Magnesium burns with an intensely bright white flame, producing a fine white powder. c) Describe the product of the reaction. The product is magnesium oxide, which is a white, powdery solid. d) Write a balanced chemical equation for the reaction. $$ 2\text{Mg(s)} + \text{O}_2\text{(g)} \rightarrow 2\text{MgO(s)} $$ e) Draw a diagram of the balanced chemical equation, using circles to represent the atoms and molecules. A diagram would show: • Two individual circles representing magnesium atoms (Mg). • One pair of circles joined together representing an oxygen molecule ($\text{O}_2$). • An arrow pointing to two structures, each consisting of one magnesium circle bonded to one oxygen circle, representing magnesium oxide molecules (MgO). 8. What conditions are required to form rust? The two conditions required to form rust are the presence of both oxygen and water (or moisture). 9. Describe two methods of reducing rust formation. • Painting or coating: Applying a layer of paint, plastic, or grease to the metal surface creates a barrier that prevents oxygen and water from reaching the iron. • Galvanizing: This involves coating the iron with a layer of zinc. Zinc is more reactive than iron, so it corrodes preferentially, protecting the iron (sacrificial protection). That's 2 down. 3 left today — send the next one.