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OCR Chemistry A Level 2015 > Enthalpy Changes > Flashcards

Flashcards in Enthalpy Changes Deck (13)
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1

What is enthalpy?

The heat content that is stored in a chemical system

2

What is exothermic?

A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to surroundings

3

What is endothermic?

A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from surroundings

4

What is standard state?

Physical state of a substance under standard conditions of 100kPa and 298K

5

What is the standard enthalpy change of a reaction?

The enthalpy change that accompanies a reaction in molar quantities expressed in a chemical equation under standard conditions, all products and reactants being in their standard states

6

What is the standard enthalpy change of combustion?

Enthalpy change when one mole of a substance reacts completely with O2 under standard conditions, all reactants and products in their standard states

7

What is the standard enthalpy change of formation?

Enthalpy change when one mole of a compound is formed from its constituent elements in their standard states under standard conditions

8

What is the standard enthalpy change of neutralisation?

Enthalpy change when one mole of water is formed in a neutralisation reaction

9

What is specific heat capacity?

Energy required to raise temperature of 1g of a substance by 1C

10

What is the average bond enthalpy?

The average bond enthalpy change when breaking by homolytic fission one mole of a given bond in molecules of a gaseous species

11

What is Hess' law?

States if a reaction can take place by more than one route, and initial and final conditions are the same, total enthalpy change is the same for each route

12

In terms of bond breaking and making, outline exothermic reactions

Energy released in bond making is greater than energy taken in during bond breaking

13

In terms of bond breaking and making, outline endothermic reactions

Energy released in bond making is less than energy taken in during bond breaking