In an experiment, metals Q, R, T and Z are reacted with aqueous nitrates of the metals (results in the table). Each of the metals has the same number of valency electrons.

1. aSuggest the valency of the metals. [1]
2. bArrange the metals in order of decreasing reactivity, starting with the most reactive. [1]
3. cNitrates of the metals decompose when heated giving nitrogen dioxide, NO₂. Which nitrate will most readily decompose when heated? Explain your answer. [2]
4. dName two other products of the decomposition of metal nitrates. [2]
5. eSuggest a chemical test to confirm that nitrogen dioxide gas is acidic. [2]

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