Flashcards
Enthalpy Changes
Cards in this deck (19)
- 1What is enthalpy change?Enthalpy change (ΔH) is the heat energy transferred in a reaction at constant pressure. The units of ΔH are kJmol⁻¹
- 2What does this symbol mean:It shows that the measurements were made under standard conditions and that the elements were in their standard states
- 3What are the standard conditions?100kPa (about 1 atm) pressure
298K (25°C) temperature - 4You can't directly measure the actual enthalpy of a system. What is used instead?Enthalpy change - you can find these either by experiment or in data books
- 5Complete the sentences: Enthalpy changes in data books are usually _____________ enthalpy changes. This is important as changes in enthalpy are affected by ______________ and ____________.Enthalpy changes in data books are usually STANDARD enthalpy changes. This is important as changes in enthalpy are affected by PRESSURE and TEMPERATURE.
- 6What does this symbol mean:Standard enthalpy change of reaction
- 7Define standard enthalpy change of reactionThe enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation, under standard conditions with all reactants and products in their standard states
- 8What does this symbol mean:Standard enthalpy change of formation
- 9Define standard enthalpy change of formationThe enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
- 10What does this symbol mean:Standard enthalpy change of combustion
- 11Define standard enthalpy change of combustionThe enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions with all reactants and products in their standard states
- 12What does this symbol mean:Standard enthalpy change of neutralisation
- 13Define standard enthalpy change of neutralisationThe enthalpy change when solutions of an acid and an alkali react together to form 1 mole of water, under standard conditions
- 14Complete the sentences: Exothermic reactions _______ ______ energy to their surroundings. The products of the reaction end up with _______ energy than the reactants. This means that the enthalpy change for the reaction will be ___________.Exothermic reactions GIVE OUT energy to their surroundings. The products of the reaction end up with LESS energy than the reactants. This means that the enthalpy change for the reaction will be NEGATIVE.
- 15TRUE OR FALSE: Oxidation is usually exothermicTRUE
- 16Describe what an enthalpy diagram of an exothermic reaction looks like
- 17Complete the sentences: Endothermic reactions ______ ____ energy from their surroundings. This means that the products of the reaction have ______ energy than the reactants, so the enthalpy change for the reaction is ___________.Endothermic reactions TAKE IN energy from their surroundings. This means that the products of the reaction have MORE energy than the reactants, so the enthalpy change for the reaction is POSITIVE.
- 18TRUE OR FALSE: Thermal decomposition is endothermicTRUE
- 19Describe what an enthalpy diagram of an endothermic reaction looks like
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- A level Chemistry (3.2 Physical Chemistry) Flashcards on Enthalpy Changes, created by Yinka F on 04/03/2018.
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- Yinka F
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