Pb + Mg(NO₃)₂ → Pb(NO₃)₂ + Mg
This reaction would NOT occur because Pb is less reactive than Mg and as such Pb cannot displace the Mg in order for the reaction to occur under normal conditions.
Mg + Fe(NO₃)₂ → Fe + Mg(NO₃)₂
This reaction would occur. This is because Mg is more reactive than Fe and as such can displace it in the reaction, thus allowing the reaction to occur under normal conditions.
Cu + Mg(NO₃)₂ → Cu(NO₃)₂ + Mg
This reaction would NOT occur. Mg is more reactive than Cu, and as such copper cannot displace magnesium in order for the reaction to occur under normal conditions.
Mass C₂H₂ needed : 22.165 g
<h3>Further explanation</h3>
Reaction
2C₂H₂+
5O₂ ⇒ 4CO₂ + 2H₂O
75.0 grams of CO₂ , mol CO₂ (MW=44 g/mol) :

mol C₂H₂ :

mass C₂H₂ (MW=26 g/mol) :

it must be a eukaryote because prokaryotic dna floats inside of it.