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Calculate H for The Following Reaction C2h4 H2 C2h6

Reviewed by Calculator Editorial Team

This calculator helps you determine the enthalpy change (ΔH) for the reaction C2H4 + H2 → C2H6. Enthalpy change is a measure of the heat absorbed or released in a chemical reaction, expressed in kilojoules per mole (kJ/mol).

Introduction

The reaction C2H4 + H2 → C2H6 is an example of an exothermic reaction, where heat is released. Calculating the enthalpy change for this reaction is essential in chemistry for understanding reaction energetics and designing efficient chemical processes.

This guide explains how to calculate ΔH for this reaction using standard enthalpy values of formation. We'll cover the formula, assumptions, and practical applications of the calculation.

How to Use This Calculator

To use the calculator:

  1. Enter the standard enthalpy of formation values for the reactants and products.
  2. Click "Calculate" to compute the enthalpy change.
  3. Review the result and interpretation.

The calculator uses the standard formula for enthalpy change of reaction:

ΔH_reaction = ΣΔHf(products) - ΣΔHf(reactants)

Formula and Assumptions

The enthalpy change for a reaction is calculated using the standard enthalpies of formation (ΔHf) of the products and reactants. The formula is:

ΔH_reaction = ΣΔHf(products) - ΣΔHf(reactants)

Assumptions:

  • The reaction occurs under standard conditions (25°C and 1 atm pressure).
  • All reactants and products are in their standard states.
  • The enthalpy change is independent of the path taken.

Worked Example

Let's calculate ΔH for the reaction C2H4 + H2 → C2H6 using standard enthalpy values:

  • ΔHf(C2H4) = -141.1 kJ/mol
  • ΔHf(H2) = 0 kJ/mol
  • ΔHf(C2H6) = -174.8 kJ/mol

Using the formula:

ΔH_reaction = [-174.8] - [-141.1 + 0] = -174.8 + 141.1 = -33.7 kJ/mol

The negative sign indicates the reaction is exothermic, releasing 33.7 kJ of heat per mole of C2H6 formed.

Interpreting Results

The calculated ΔH value tells you:

  • A positive ΔH means the reaction is endothermic (absorbs heat).
  • A negative ΔH means the reaction is exothermic (releases heat).
  • The magnitude indicates the energy change per mole of reaction.

In our example, ΔH = -33.7 kJ/mol shows the reaction releases 33.7 kJ of heat per mole of C2H6 produced.

FAQ

What is the standard enthalpy of formation?
The standard enthalpy of formation (ΔHf) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states.
How do I find standard enthalpy values?
Standard enthalpy values can be found in chemistry reference books, online databases, or government sources like the National Institute of Standards and Technology (NIST).
What units are used for ΔH?
ΔH is typically measured in kilojoules per mole (kJ/mol) or calories per mole (cal/mol).
Can ΔH be negative?
Yes, a negative ΔH indicates an exothermic reaction where heat is released to the surroundings.
How accurate is this calculator?
The calculator provides an estimate based on standard conditions. For precise industrial applications, consult specialized chemical engineering resources.