Calculate Delta H for Reaction of 0.105g Ethylene

Introduction

The enthalpy change (ΔH) measures the heat absorbed or released during a chemical reaction at constant pressure. For reactions involving ethylene (C₂H₄), ΔH helps predict reaction feasibility, energy requirements, and product stability.

This calculator specifically handles reactions where 0.105g of ethylene is involved. The calculation requires knowing the standard enthalpy of formation (ΔH°f) for all reactants and products, as well as the stoichiometry of the reaction.

How to Calculate Delta H

To calculate ΔH for a reaction involving ethylene:

1. Identify the balanced chemical equation for the reaction.
2. Determine the standard enthalpy of formation (ΔH°f) for all reactants and products.
3. Calculate the total enthalpy for reactants and products using their ΔH°f values.
4. Compute ΔH for the reaction using the formula below.

For reactions with ethylene, common reactions include combustion and hydrogenation. The calculator uses standard thermodynamic data for accurate results.

Formula

The enthalpy change for a reaction is calculated using the standard enthalpies of formation:

Where:

• ΔH°f = standard enthalpy of formation (kJ/mol)
• Σ = sum of all products or reactants

For reactions involving 0.105g of ethylene, the mass must first be converted to moles using the molar mass of ethylene (28.05 g/mol).

Worked Example

Consider the combustion of ethylene:

Given:

• Mass of ethylene = 0.105g
• ΔH°f for C₂H₄ = -14.1 kJ/mol
• ΔH°f for CO₂ = -393.5 kJ/mol
• ΔH°f for H₂O = -285.8 kJ/mol

Calculation steps:

1. Convert mass to moles: 0.105g ÷ 28.05 g/mol = 0.00374 mol C₂H₄
2. Calculate total ΔH°f for reactants: 0.00374 mol × (-14.1 kJ/mol) = -0.0527 kJ
3. Calculate total ΔH°f for products: (2 × 0.00374 mol × -393.5 kJ/mol) + (2 × 0.00374 mol × -285.8 kJ/mol) = -0.581 kJ
4. Compute ΔH: -0.581 kJ - (-0.0527 kJ) = -0.528 kJ

The reaction releases 0.528 kJ of heat for 0.105g of ethylene.

Interpreting Results

A negative ΔH indicates an exothermic reaction (heat released), while a positive ΔH indicates an endothermic reaction (heat absorbed). For ethylene reactions:

• Combustion is typically exothermic (ΔH < 0).
• Hydrogenation is usually endothermic (ΔH > 0).

Results help determine reaction feasibility, energy requirements, and product stability. Always verify standard enthalpy values with reliable sources like the National Institute of Standards and Technology (NIST).