To determine the reactants for the given synthesis reaction, we start with the balanced synthesis reaction:
\[ 2 ; ___ + ___ ; \rightarrow ; (N_2H_4) ; \cdot ; 2SO_4 \]
Given the product \( N_2H_4 \) (hydrazine) and \( SO_4 \) (sulfate), we need to identify which reactants lead to this synthesis reaction.
Looking at the given reactants:
- \( N_2H_4 \) (hydrazine)
- \( H_2SO_4 \) (sulfuric acid)
- \( N_3 \) (ammonia)
- \( N_2H_8 \) (not a common molecule)
- \( SO_4 \) (sulfate ion, needs to be with a cation)
In order to produce \( N_2H_4 \) and sulfate \( SO_4 \), the likely reactants would be:
- Two molecules of hydrazine: \( N_2H_4 \)
- One molecule of sulfuric acid: \( H_2SO_4 \)
Thus, the balanced synthesis reaction could be shown as:
\[ 2 ; N_2H_4 + H_2SO_4 ; \rightarrow ; (N_2H_4)\cdot 2SO_4 \]
Based on this, the filled-in balanced synthesis reaction would look like:
Final Answer: \[ 2 ; N_2H_4 + H_2SO_4 ; \rightarrow ; (N_2H_4) \cdot 2SO_4 \]