1. Unit 20 Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals / Reference in textbook: Section 20.15 ST

2. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) Observations 5Record your observations.

3. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) Discussion 6a)What is the gas given off when magnesium reacts with very dilute nitric acid? _______________________________________________________ b) Is there any reaction between copper and very dilute nitric acid? _______________________________________________________ c) Does very dilute nitric acid react like a typical acid? _______________________________________________________ Hydrogen No Very dilute nitric acid reacts like a typical acid.

4. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) 7In the reaction between dilute nitric acid and magnesium / copper, colourless nitrogen monoxide (NO) gas is given off. When nitrogen monoxide gas mixes with air, it changes to brown nitrogen dioxide (NO 2 ) gas. a)Oxidation number of nitrogen in NO 3 – = __________ Oxidation number of nitrogen in NO = __________ b) What is the change of the oxidation number of nitrogen in the reactions? ___________________________________________________________ c)Does dilute nitric acid act as a typical acid or an oxidizing agent? ___________________________________________________________ Dilute nitric acid acts as an oxidizing agent. From +5 to +2 +5 +2

5. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) 8In the reaction between concentrated nitric acid and magnesium / copper, brown nitrogen dioxide (NO 2 ) gas is given off. a)Oxidation number of nitrogen in NO 3 – = __________ Oxidation number of nitrogen in NO 2 = __________ b)What is the change of the oxidation number of nitrogen in the reactions? ___________________________________________________________ c) Does concentrated nitric acid act as a typical acid or an oxidizing agent? ___________________________________________________________ +5 +4 From +5 to +4 Concentrated nitric acid acts as an oxidizing agent.

6. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) Conclusion 9Very dilute nitric acid acts as an ( acid / oxidizing agent ) when it reacts with metals high in the reactivity series. ____________ gas is given off in the reactions. 10Dilute nitric acid and concentrated nitric acid act as ( acids / oxidizing agents ) when they react with metals. Hydrogen

7. Unit 20Oxidation and reduction Activity 20.3 Investigating the action of nitric acid of different concentrations on metals (S)/(T) Question 11Write an ionic equation for each of the following reactions.