14.1.6

Molar Enthalpy Change

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Molar Enthalpy Change

The change in heat during a reaction carried out at a constant pressure is known as an enthalpy change. We can work out the enthalpy change per mole of substance. This is called the molar enthalpy change and the symbol for this is ΔH.

Step 1

Step 1

  • Work out the enthalpy change using the equation:
    • Heat energy transferred = mass × specific heat capacity × temperature change
    • Q = mcΔT
Step 2

Step 2

  • Calculate the number of moles using the equation:
    • moles = mass ÷ relative formula mass (Mr)
    • mol = m ÷ Mr
Step 3

Step 3

  • Divide the heat energy transferred by the number of moles.
    • Molar enthalpy change = heat energy transferred ÷ moles.
    • ΔH = Q ÷ mol
Jump to other topics
1

States of Matter

1.1

States of Matter

1.1.1States of Matter1.1.2Simple Sphere1.1.3Changes of State1.1.4Changes of State 21.1.5Changes of State 31.1.6Changes of State and Temperature1.1.7Solubility1.1.8Solubility Curves1.1.9Solubility - Experiments1.1.10Diffusion - Experiment1.1.11Changing State HyperLearning
2

Elements, Compounds & Mixtures

2.1

Elements, Mixtures & Compounds

2.1.1Elements & Compounds2.1.2Chemical Formula2.1.3Mixtures2.1.4Purity2.1.5Separating Mixtures2.1.6Separating Mixtures 22.1.7Paper Chromatography2.1.8Paper Chromatography Analysis2.1.9Paper Chromatography - Practical2.1.10End of Topic Test - Elements,Compounds,Mixtures2.1.11Grade 9 - Chromatography2.1.12Exam-Style Questions - Separation of Mixtures
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Atomic Structure

3.1

Atoms

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The Periodic Table

4.1

The Periodic Table

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Chemical Formulae, Equations & Calculations

5.1

Equations

5.1.1Forming Equations5.1.2Balancing Symbols5.1.3State Symbols5.1.4Relative Formula Mass5.1.5Calculating Relative Formula Mass5.1.6Relative Formula Mass - Calculations5.1.7Introducing Moles5.1.8Relative Formula Mass5.1.9Amounts of Substance5.1.10Moles & Yield5.1.11Moles - Calculations5.1.12Balancing Equations5.1.13Moles to Balance Equations5.1.14Limiting Reactants5.1.15Chemical Measurements5.1.16Calculating Mass5.1.17Changing Mass5.1.18Exam-Style Questions - Moles5.1.19Percentage Yield5.1.20Calculating Yield5.1.21Percentage Yield - Calculations5.1.22Empirical & Molecular Formula5.1.23Experiment for Empirical Formula5.1.24Empirical Formula - Calculations5.1.25Concentrations & Amounts5.1.26Conclusion of Solutions5.1.27Volumes and Gases5.1.28Concentration & Amounts - Calculations5.1.29End of Topic Test - Equations5.1.30Grade 9 - Equations
6

Bonding

6.1

Ionic Bonding

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6.2

Covalent Bonding

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6.3

Metallic Bonding

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Electrolysis

7.1

Electrolysis

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8

Groups of the Periodic Table

8.1

Alkali Metals & Halogens

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The Atmosphere

9.1

Gases in the Atmosphere

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Reactivity Series

10.1

Reactivity Series

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11

Metal Extraction

11.1

Metal Extraction

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12

Acids & Alkalis

12.1

Acids, Alkalis & Titrations

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Identifying Gases

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Testing Anions, Cations & Water

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14

Physical Chemistry

14.1

Energetics

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15

Organic Chemistry

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Hydrocarbons

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Esters

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15.6

Synthetic Polymers

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End of Topic - Organic Chemistry

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Practice questions on Molar Enthalpy Change

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  1. 1
    What's the symbol for molar enthalpy change?Multiple choice
  2. 2
    Working out Molar Enthalpy ChangePut in order
  3. 3
    Which of these is _not_ an equation you need to use to work out molar enthalpy change?Multiple choice
  4. 4
    A student experimented to determine the molar enthalpy change of a certain reaction. The mass of the reactants used was 10 grams and the heat energy transferred was 500 J. The relative formula mass (Mr) of the reactants was 20 g/mol. What is the molar enthalpy change for this reaction?Multiple choice
  5. 5
    A chemical reaction is known to have a molar enthalpy change of -600 kJ/mol. Which of the following statements is correct regarding the reaction?Multiple choice
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Calculating Heat Energy Transferred

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