When a solution of Pb(NO3)2(aq) is mixed with a solution of KI(aq), a precipitate of PbI₂ will form; K⁺ and NO₃⁻ are spectator ions.
<u>Explanation:</u>
When an aqueous solution of lead nitrate (Pb(NO₃)₂ is mixed with aqueous solution of potassium iodide (KI), then there is a precipitate formation of lead iodide (PbI₂), and the potassium (K⁺) ion and nitrate (NO₃⁻) ion acts as spectator ions that is ions do not involved in the reaction.
The reaction can be represented as,
Pb(NO₃)₂(aq) + 2 KI (aq) → PbI₂(s) + 2KNO₃(aq)
The ionic equation can be written as,
Pb²⁺(aq) + 2 NO₃⁻(aq) + 2 K⁺(aq) + 2 I⁻(aq) → PbI₂(s) + 2K⁺(aq) + 2NO₃⁻(aq)
On both sides of the equation, we have K⁺ and NO₃⁻ ions, which gets cancelled, and these 2 ions are called as spectator ions.
magnesium oxide is: MgO (right side)
so the left side is: Mg + O2
for the equation to be balanced there must be two oxygens on both sides
Mg + O2 = 2MgO
but now the magnesium is uneven, so there must be two magnesiums on each side
the answer is: B) 2Mg + O2 = 2MgO
