The set-up below was used to investigate the properties of hydrogen. (i) State two observations that was made in the combustion tube as the reaction progressed

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13. Below is a simplified scheme of solvay process. Study it and answer the questions that follow.

• 13a) Identify gas R. In the Solvay process, ammonia solution is reacted with carbon dioxide (Gas R) and brine to form ammonium bicarbonate, which then reacts further. Gas R: $\boxed{\text{Carbon dioxide (CO}_2\text{)}}$

• 13b) Write an equation for process III. Process III involves the thermal decomposition of sodium bicarbonate ($NaHCO_3$) to produce sodium carbonate ($Na_2CO_3$), water, and carbon dioxide.

  $$2\text{NaHCO}_3\text{(s)} \xrightarrow{\text{heat}} \text{Na}_2\text{CO}_3\text{(s)} + \text{H}_2\text{O(g)} + \text{CO}_2\text{(g)}$$

• 13c) Give one use of sodium carbonate. Sodium carbonate is a versatile industrial chemical. One use: $\boxed{\text{Manufacture of glass}}$ (Other uses include making detergents, softening hard water, and in paper manufacturing).

14. The set-up below was used to investigate the properties of hydrogen.

• 14i) State two observations that were made in the combustion tube as the reaction progressed. In the combustion tube, hydrogen gas reacts with heated Lead(II) oxide (PbO). Hydrogen acts as a reducing agent, reducing the lead(II) oxide to lead metal and forming water. $$\text{H}_2\text{(g)} + \text{PbO(s)} \xrightarrow{\text{heat}} \text{Pb(s)} + \text{H}_2\text{O(g)}$$
  1. The yellow/orange solid (Lead(II) oxide) turned into a grey solid (Lead metal).
  2. Colourless liquid droplets (water) were observed on the cooler parts of the combustion tube.