Answer:
Step-by-step explanation:
The equations in each option are confusing (repeated) but understandable
Balancing a chemical equation means the same number of individual and overall atoms on the reactant side is equal to the same number of individual and overall atoms on the product side. This is based on the law of conservation of matter which states that matter can neither be created nor destroyed, hence the no atom must be unaccounted for on any side.
The balancing of these equations seem to test the knowledge of a particular trick in balancing of equation - which will be highlighted as the equation is balanced
(a) To balance
SiO₂(s) + C(s) ⇒ Si(s) + CO(g)
The balanced equation will be
SiO₂(s) + 2C(s) ⇒ Si(s) + 2CO(g)
NOTE: The best way to address equations like this to balance the uniatomic element last.
(b) SiCl₄(l) + Mg(s) ⇒ Si(s) + MgCl₂(s)
The balanced equation will be
SiCl₄(l) + 2Mg(s) ⇒ Si(s) + 2MgCl₂(s)
NOTE: As noted earlier, the uniatomic molecule should be balanced last
(c) To balance
Na₂SiF₆(s) + Na(s) ⇒ Si(s) + NaF(s)
The balanced equation will be
Na₂SiF₆(s) + 4Na(s) ⇒ Si(s) + 6NaF(s)
NOTE: As noted earlier, the uniatomic molecule should be balanced last
Please, always sum the number of individual and overall atoms on both sides when you are done answering questions like this just to be sure.