Attempt the question, check the explanation, and continue with similar questions to build confidence before exams.
NaOH + HCl → NaCl + H2O
CaCO3 + H2 → Ca + CO2
CH3COOH + Na → CH3COONa + H2
H2 + O2 → H2O
Continue with nearby questions to strengthen the same chapter concept while you still have the context fresh in mind.