Question

Predict the missing component of each reaction.

? + 2 upper N a upper B r right arrow 2 upper N a upper C l plus upper B r subscript 2.

HCl

Cl2

Na

HBr
right arrow upper M g upper O plus upper H subscript 2. ?

CHO

C2H2 + CO2

CO2 + 2H2O

C + 2H2O

Answer 1

I can answer the first one confidently, but the rest of the input looks garbled — could you reformat those reactions? Meanwhile:

1) ? + 2 NaBr → 2 NaCl + Br2
Missing reagent: Cl2
Reason: Cl2 displaces Br− (Cl2 + 2 NaBr → 2 NaCl + Br2).

2) If the reaction shown is producing MgO + H2, the reactants would be magnesium and steam:
Mg + H2O → MgO + H2
(steam oxidizes Mg to MgO and releases H2).

If you post the remaining reactions each on its own line (with any answer choices), I’ll fill in the missing components.