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Practice each question, then open the answer or worked solution.
Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
When an iron nail is dipped in the copper sulphate solution, iron displaces copper from the copper sulphate because iron is more reactive than copper. Therefore, the colour of the copper sulphate solution changes. The reaction is
Fe + CuSO4 → FeSO4 + Cu
Give an example of a double displacement reaction other than the one given in Activity 1.10.
Reaction Between silver nitrate (AgNO3) and Sodium chloride (NaCl) is an example of a double displacement reaction. During the reaction, negative and positive ions trade positions as a result of the formation of white silver chloride precipitate. The chemical reaction is given below.
Ag+ + NO3– + Na+ + Cl– → AgCl + Na+ + NO3–
Identify the substances that are oxidised and that are reduced in the following equation.
i) 4Na(s) + O2(g) → 2Na2O(s)
ii) CuO(s) + H2(g) → Cu(s) + H2O(l)
The Sodium (Na) in the first equation is getting oxidized with the addition of Oxygen (O2), and the Copper (Cu) in the second equation is reduced due to the addition of Hydrogen (H2).