Identify Gas K and Liquid T, write the balanced chemical equation for their reaction, and explain why Gas K is passed through the combustion tube before heating starts.

Gas K burns with a blue flame and a pop sound. This is a characteristic test for hydrogen gas.

a) (i) Gas K: $\boxed{\text{Hydrogen}}$

Gas K (hydrogen) reacts with heated Lead (II) Oxide ($PbO$). Hydrogen is a reducing agent. It will reduce $PbO$ to lead ($Pb$) and form water ($H_2O$). Liquid T is the product of this reaction that is liquid at room temperature.

a) (ii) Liquid T: $\boxed{\text{Water}}$

The reaction is between hydrogen gas ($H_2$) and lead (II) oxide ($PbO$). Hydrogen reduces lead (II) oxide to lead metal ($Pb$) and forms water ($H_2O$).

$$H_2(g) + PbO(s) \longrightarrow Pb(s) + H_2O(l)$$

b) Equation: $\boxed{H_2(g) + PbO(s) \longrightarrow Pb(s) + H_2O(l)}$

Gas K (hydrogen) forms an explosive mixture with air (oxygen). Passing hydrogen through the tube before heating starts removes all the air from the tube, preventing an explosion when the hydrogen is heated.

c) Reason: Hydrogen gas forms an explosive mixture with air. Passing hydrogen through the tube before heating removes air, preventing an explosion.