Why do fireflies glow at night?

"$A$ solution of potassium chloride when mixed with silver nitrate solution, an insoluble white substance is formed".
$(i)$ Translate the above statement into a chemical equation.

Complete the missing components/variables given as $x$ and $y$ in the following reactions:
$(a)$ $Pb(NO_3)_2(aq) + 2KI(aq) \longrightarrow PbI_2(x) + 2KNO_3(y)$
$(b)$ $Cu(s) + 2AgNO_3(aq) \longrightarrow Cu(NO_3)_2(aq) + x(s)$

Explain the type of reaction represented by the following equation:
$(i) \ CuSO_{4} + 2NaOH \longrightarrow Cu(OH)_{2} + Na_{2}SO_{4}$

The colour formed on the surface of copper powder when it is heated in a china dish is:

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.