The following thermochemical equation is for the reaction of carbon dioxide(g) with hydrogen(g) to form carbon monoxide(g) and water(g). CO2(g) + H2(g) CO(g) + H2O(g) H = 41.2 kJ

Question

When 15.0 grams of carbon dioxide(g) react with excess hydrogen(g),  _________ kJ of energy are evolved or absorbed?

Answer 1

Hello, Jaden,

I will need to assume that the value of H provided in your question is in units of kJ/mole, not just kJ.

The balanced equation is: CO₂ + H₂ = CO + H₂O

We can then read the equation as " One mole of CO₂ reacts with one mole of H₂ to produce one mole each of CO and water, and that this requires 41.2 kJ to proceed per mole of CO₂ consumed.

That values is thus 41.2 kJ/mole CO₂.

We have 15 grams of CO₂. Convert that into moles CO₂ by dividing by nthe molar mass of CO₂.

15 g/\44.0 g/mole = 0.341 moles CO₂.

The heat required to convert 15 grams of carbon dioxide is thus (0.341 moles CO₂)*(41.2 kJ/mole CO₂) = 14.0 kJ.

Since H is positive, energy is absorbed by the reaction. The resulting products from the 15 grams of CO₂ and excess hydrogen have an additional 14.0kJ over that contained in the reactants.

Bob