IB Chemistry Topic R1.1.4 Standard Enthalpy Change Revision Notes (SL/HL)

IB Chemistry Topic R1.1.4 Standard Enthalpy Change Revision Notes (SL/HL) | RevisionDojo

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Understanding Standard Enthalpy Change and Heat Calculations

What is Standard Enthalpy Change ($\Delta H^\ominus$)?

Definition

Enthalpy change

The enthalpy change (ΔH) of a reaction quantifies the heat exchanged at constant pressure during a chemical or physical change.

Chemical reactions are accompanied by energy transfers between the system (reactants and products) and the surroundings.
The standard enthalpy change ($\Delta H^\ominus$) is the heat transferred at constant pressure under standard conditions: 298 K (25°C), 100 kPa, with reactants and products in their standard states.
1. Exothermic reactions: release heat to the surroundings, giving a negative $\Delta H$ (for example, combustion of fuels).
2. Endothermic reactions: absorb heat from the surroundings, giving a positive $\Delta H$ (for example, melting ice).

Units of Enthalpy Change

The standard unit for $\Delta H$ is kilojoules per mole (kJ mol⁻¹).
This reflects the energy change per mole of reactant or product under standard conditions.

Tip

Always give your final answer for $\Delta H$ in kJ mol⁻¹.
If $Q$ is calculated in joules, convert it to kilojoules by dividing by 1000.

Calculating Heat Transfer (Q)

The heat transferred during a reaction can be calculated using: $$Q = mc\Delta T$$ where:

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Understanding Standard Enthalpy Change and Heat Calculations

What is Standard Enthalpy Change ($\Delta H^\ominus$)?

Definition

Enthalpy change

The enthalpy change (ΔH) of a reaction quantifies the heat exchanged at constant pressure during a chemical or physical change.

Chemical reactions are accompanied by energy transfers between the system (reactants and products) and the surroundings.
The standard enthalpy change ($\Delta H^\ominus$) is the heat transferred at constant pressure under standard conditions: 298 K (25°C), 100 kPa, with reactants and products in their standard states.
1. Exothermic reactions: release heat to the surroundings, giving a negative $\Delta H$ (for example, combustion of fuels).
2. Endothermic reactions: absorb heat from the surroundings, giving a positive $\Delta H$ (for example, melting ice).

Units of Enthalpy Change

The standard unit for $\Delta H$ is kilojoules per mole (kJ mol⁻¹).
This reflects the energy change per mole of reactant or product under standard conditions.

Tip

Always give your final answer for $\Delta H$ in kJ mol⁻¹.
If $Q$ is calculated in joules, convert it to kilojoules by dividing by 1000.

Calculating Heat Transfer (Q)

The heat transferred during a reaction can be calculated using: $$Q = mc\Delta T$$ where:

Definition

Paywall

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Note

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Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
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Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

IB Chemistry R1.1.4 Standard Enthalpy Change Notes

Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

Understanding Standard Enthalpy Change and Heat Calculations

What is Standard Enthalpy Change ($\Delta H^\ominus$)?

Units of Enthalpy Change

Calculating Heat Transfer (Q)

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Duis aute irure dolor in reprehenderit

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Understanding Standard Enthalpy Change and Heat Calculations

What is Standard Enthalpy Change ($\Delta H^\ominus$)?

Units of Enthalpy Change

Calculating Heat Transfer (Q)

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

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