List two observations which you record while burning magnesium in air.

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

Which among the following is(are) double displacement reaction$(s)$?
$(i)$ $Pb + CuCl_{2} \rightarrow PbCl_{2} + Cu$
$(ii)$ $Na_{2}SO_{4} + BaCl_{2} \rightarrow BaSO_{4} + 2NaCl$
$(iii)$ $C + O_{2} \rightarrow CO_{2}$
$(iv)$ $CH_{4} + 2O_{2} \rightarrow CO_{2} + 2H_{2}O$

Which one is a chemical change: Electrolysis of water or Sodium chloride exposed to sunlight?

The reaction which is used in black and white photography is:

When potassium iodide solution is added to a solution of lead $(II)$ nitrate in a test tube,a precipitate is formed.
$(i)$ Write a balanced chemical equation for this reaction.
$(ii)$ What type of reaction is this?