On Easter Sunday, April 23, 1983, nitric acid spilled from a tank car near downtown Denver, Colorado. The spill was neutralized with sodium carbonate.

Question

2 HNO3(aq) + Na2CO3(s) 2 NaNO3(aq) + H2O(l) + CO2(g)

(a) Calculate H° for this reaction.
kJ
Approximately 1.0 104 gal nitric acid was spilled. Assume that the acid was an aqueous solution containing 75.0% HNO3 by mass with a density of 1.42 g/cm3. How much sodium carbonate was required for complete neutralization of the spill? (Hf° for NaNO3(aq) = -467 kJ/mol.)
g
How much heat was evolved?
kJ

(b) According to The Denver Post for April 4,1983, authorities feared that dangerous air pollution might occur during the neutralization. Considering the magnitude of H°, what was their major concern?

Answer 1

I can help you with (a) but the rest I can't.
the answer is -68.5
To get this answer you need to subtract the H° of the reactants from the H° of the products.

[(2*-467)+(-286)+(-393.5)]-[(2*-207)+(-1131)=-68.5