Explain what the sign of ΔH tells you about the energy changes involved in the reaction.
If ΔH is positive, energy is transferred from the surroundings to the system. The temperature of the surroundings decreases and the reaction is endothermic.
If ΔH is negative, energy is transferred from the system to the surroundings. The temperature of the surroundings increases and the reaction is exothermic.
What is enthalpy change a measure of?
The amount of heat energy absorbed or released during a reaction.
What sign is used to denote standard conditions?
⦵
What is enthalpy change a measure of?
The amount of heat energy absorbed or released during a reaction.
What are the typical units for enthalpy change?
kJ mol-1
What is the standard pressure in kPa?
101 kPa
What is the standard temperature in °C?
25°C
What is standard state?
The physical state of a substance under standard conditions (of 25°C and 101 kPa).
How is standard enthalpy change of formation ΔfH⦵ defined?
The enthalpy change when one mole of a compound is formed from its elements under standard conditions.
How is standard enthalpy change of combustion ΔcH⦵ defined?
The enthalpy change when one mole of a substance reacts completely with oxygen under standard conditions.
How is standard enthalpy change of formation ΔfH⦵ defined?
The enthalpy change when one mole of a compound is formed from its elements under standard conditions.
How is standard enthalpy change of neutralisation ΔH⦵neut defined?
The energy change that accompanies the neutralisation of an acid and an alkali to form one mole of water under standard conditions.
What is an enthalpy profile diagram?
A diagram that shows the energy change during a chemical reaction.
What is an endothermic reaction?
An endothermic reaction is a reaction that takes in energy from the surroundings, so the temperature of the surroundings decreases.
What is an enthalpy profile diagram?
A diagram that shows the energy change during a chemical reaction.
What is an exothermic reaction?
An exothermic reaction is a reaction that transfers energy to the surroundings, so the temperature of the surroundings increases.
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Formulae37
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2.1 Atoms, Ions and Compounds41
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2.2 Amount of Substance48
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2.3 Acids and Redox41
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2.4 Electrons, Bonding and Structure65
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2.5 Shapes of Molecules and Intermolecular Forces1
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3.1 Periodicity25
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3.2 Reactivity Trends48
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3.3 Enthalpy16
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3.4 Reaction Rates and Equilibrium0
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4.1 Basic Concepts of Organic Chemistry20
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4.2 Alkanes0
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4.3 Alkenes0
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4.4 Alcohols0
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4.5 Haloalkanes0
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4.6 Organic Synthesis0
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4.7 Spectroscopy0
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5.1 Rates of Reaction0
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5.2 Equilibrium0
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5.3 Acids, Bases and pH0
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5.4 Buffers and Neutralisation0
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5.5 Enthalpy and Entropy0
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5.6 Redox and Electrode Potentials0
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5.7 Transition Elements0
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6.1 Aromatic Chemistry0
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6.2 Carbonyls and Carboxylic Acids0
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6.3 Amines, Amino Acids and Proteins0
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6.4 Organic Synthesis0
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6.5 Chromatography and Spectroscopy0
