Can oxidation or reduction take place alone? Why or why not? What are such reactions called?

Write the balanced chemical equations for the following reactions:
$(a)$ Sodium carbonate on reaction with hydrochloric acid in equal molar concentrations gives sodium chloride and sodium hydrogencarbonate.
$(b)$ Sodium hydrogencarbonate on reaction with hydrochloric acid gives sodium chloride,water,and liberates carbon dioxide.
$(c)$ Copper sulphate on treatment with potassium iodide precipitates cuprous iodide $(Cu_2I_2)$,liberates iodine gas,and also forms potassium sulphate.

$(a)$ Why is the corrosion of iron a serious problem?
$(b)$ How can we prevent corrosion?

Write a balanced chemical equation for each of the following reactions and also classify them.
$(a)$ Lead acetate solution is treated with dilute hydrochloric acid to form lead chloride and acetic acid solution.
$(b)$ $A$ piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

An aluminium can was used to store ferrous sulphate solution. It is observed that in a few days,holes appeared in the can. Explain the observation and write the chemical equation to support your answer.

Write true or false for the following statement:
The insoluble substance formed during a chemical reaction is known as a precipitate.