The balanced thermochemical equation for the Haber process yields a theoretical ammonia yield of 20.06 g with a percent yield of 41.5%. The subsequent sections outline heat calculations and the net ionic equation for ammonia reacting with nitric acid.
The balanced thermochemical equation for the Haber process is as follows:
Nitrogen gas (N₂) + 3 Hydrogen gas (H₂) → 2 Ammonia (NH₃), ΔH = -92.4 kJ
This equation indicates that one mole of nitrogen gas (N₂) reacts with three moles of hydrogen gas (H₂) to produce two moles of ammonia (NH₃). The reaction is exothermic, releasing 92.4 kJ of heat energy.
To find the theoretical yield of ammonia, we first need to determine the limiting reactant. The balanced equation shows a 1:3 ratio between nitrogen gas and hydrogen gas. Let's calculate the moles of each reactant:
Moles of N₂ = mass / molar mass = 16.55 g / 28.02 g/mol ≈ 0.590 mol
Moles of H₂ = mass / molar mass = 10.15 g / 2.016 g/mol ≈ 5.04 mol
The ratio of moles of N₂ to H₂ is approximately 1:3, indicating that N₂ is the limiting reactant.
Now, using the stoichiometry of the reaction, we can determine the moles of NH₃ formed:
Moles of NH₃ = (moles of N₂) × (2 mol NH₃ / 1 mol N₂) ≈ 0.590 mol × 2 = 1.18 mol
Now, we can find the theoretical yield of ammonia in grams:
Theoretical Yield = (moles of NH₃) × (molar mass of NH₃) = 1.18 mol × 17.03 g/mol ≈ 20.06 g
To calculate the percent yield, we can use the formula:
Percent Yield = (Actual Yield / Theoretical Yield) × 100
Given that the actual yield is 8.33 grams, we can substitute these values into the formula:
Percent Yield = (8.33 g / 20.06 g) × 100 ≈ 41.5%
Therefore, the percent yield of ammonia is approximately 41.5%.
4: Heat Energy in Ammonia Production
Calculate moles of NH₃:
Moles = Mass / Molar Mass
Given that the molar mass of NH₃ is approximately 17.03 g/mol:
Moles = 8.33 g / 17.03 g/mol ≈ 0.489 mol
Use the coefficients in the balanced equation to relate moles of NH₃ to ΔH:
q = Moles × ΔHₙᵣₓₙ
q = 0.489 mol × ΔHₙᵣₓₙ
The sign of ΔHₙᵣₓₙ depends on whether the reaction is exothermic or endothermic.
5: Reaction of Ammonia with Nitric Acid
(a) Balanced Chemical Equation:
NH₃(g) + HNO₃(aq) → NH₄NO₃(aq)
(b) Complete Ionic Equation:
NH₃(g) + H⁺(aq) + NO₃⁻(aq) → NH₄⁺(aq) + NO₃⁻(aq)
Net Ionic Equation:
NH₃(g) + H⁺(aq) → NH₄⁺(aq)
In the net ionic equation, the nitrate ion (NO₃⁻) is a spectator ion and does not participate in the reaction. The net ionic equation focuses on the species that undergo a change.