Consider the neutralization reaction represented by the following equation: Na2CO3 + 2HNO 3 → 2NaNO3 + H2O + CO2 The stoichiometric ratio of acid to base is

Analyze the question: We need the stoichiometric ratio of acid to base in the balanced equation.

Concept: In a balanced equation, the coefficients give the mole ratio of reactants. The ratio "acid : base" means moles of acid to moles of base.

Solution:

Na₂CO₃ + 2HNO₃ → 2NaNO₃ + H₂O + CO₂

• Acid = HNO₃, coefficient 2
• Base = Na₂CO₃, coefficient 1

Acid : Base = 2 : 1

Why not the others?

• A (2:2) and D (1:1) both simplify to 1:1, which would be wrong because 2 moles of HNO₃ are needed for every 1 mole of Na₂CO₃.
• C (1:2) is the base-to-acid ratio, which is the reverse of what was asked.

Tip: Read the order in the question carefully. "Acid to base" means the acid's coefficient comes first. Always check that the equation is balanced before reading off ratios. Here it is: 2 Na, 2 N, 6 O + ... all balance on both sides.