Answer:
Balanced equation: HCHO₂ + NaOH → NaCHO₂ + H₂O
Heat of reaction: 22.6 kJ/mol
Explanation:
The chemical equation is the sum of the reactants given the products:
HCHO₂ + NaOH → NaCHO₂ + H₂O
To balance the equation, the elements must be in the same amount in the reactants and the products. As we can see, there are the same amount of elements on each side, so the equation is balanced.
The heat flows can be calculated by:
Q = m*cp*ΔT
Where m is the mass of the substances (mass of formic acid + mass of sodium hydroxide), cp is the specif heat, and ΔT is the variation at temperature (final - initial).
Mass is the density multiplied by the volume, so:
m = 1*75 + 1*45 = 120 g
Q = 120*4.18*(25.5 - 21.9)
Q = 1,805.76 J = 1.81 kJ
The number of moles of the reactants can be calculated by the volume multipled by the concentration:
HCHO₂ = 0.075L * 1.07 mol/L = 0.08025 mol
NaOH = 0.045L * 1.78 mol/L = 0.0801 mol
So, NaOH is limiting (stoichiometry is 1:1, so it's necessary the same amount of the reactants), and the heat of the reaction will be calculated by it.
ΔH = Q/n
ΔH = 1.81/0.0801
ΔH = 22.6 kJ/mol
