A flowchart shows reactions starting with lead (II) carbonate. State the condition in step 1 and identify Reagent K and Gas Q.

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6. The flow chart below shows some reactions starting with lead (II) carbonate. Study it and answer the questions that follow.

   i) State the condition necessary in step 1. (1 mark)
   Step 1 involves the decomposition of lead (II) nitrate to nitrogen (IV) oxide. This reaction requires heat.

   • Heating

   ii) Identify (3 marks)

   • I Reagent K Step 6 shows lead (II) carbonate reacting with Reagent K to form aqueous lead (II) nitrate. Lead (II) carbonate is an insoluble salt, and to convert it to a soluble nitrate, it must react with nitric acid.

     $$\text{PbCO}_{3}(\text{s}) + 2\text{HNO}_{3}(\text{aq}) \rightarrow \text{Pb(NO}_{3})_{2}(\text{aq}) + \text{H}_{2}\text{O}(\text{l}) + \text{CO}_{2}(\text{g})$$
     • Nitric acid ($\text{HNO}_{3}$)

   • II Gas Q Step 1 shows lead (II) nitrate decomposing to form nitrogen (IV) oxide, which is Gas Q.

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