Chapter 9 Enthalpy Flashcards
1
Q
What is enthalpy
A
- measure of heat energy in a chemical system
- chemical system -atoms ,molecules or ions making up the chemicals
- energy stored within bonds
2
Q
How do you calculate enthalpy change
A
reactants - products
3
Q
what is the law of conservation of energy
A
- energy cannot be created or destroyed
4
Q
What happens with a chemical reaction involving an enthalpy change
A
- system is the chemicals - reactants and prodcts
- surrounding are apparatus and labatories whcih are not the chemical system
- universe is everything includes both system and surroundings
5
Q
What is an exothermic reaction
A
- energy transferred from system to the surrounding
- enthalpy change in negative
- temperature of the surroundings increases as they gain energy
6
Q
What is an endothermic reaction
A
- energy transferred from the surroundings to the system
- enthalpy change is potitive
- temperature of the surroundings decreases as they lose energy
7
Q
What is the activation energy
A
- is the minimum amount of energy required for a reaction to take place
8
Q
What are standard conditions
A
- pressure - 100Kpa
- standard temperature 298K
- concentration - 1moldm-3
- standard tate physical stat of the substance under standard conditions
9
Q
What is standard enthalpy change of reaction
A
- enthalpy change that accompanies a reaction in molar quantities expressed in a chemical equation under standard conditions all reactants and products being in their standard states
10
Q
What is standard enthalpy change of combustion
A
- the enthalpy change that takes place when one mole of a substance reacts completley with oxygen under standard condition al reactants and products being in their strandard states
11
Q
What is standard enthalpy change of formation
A
- the enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under their standard states
12
Q
What is the standard enthalpy change of neutralisation
A
- the enthalpy change that accompanies the reaction of an acid by a base to form one mole fo H2O under standard conditions
13
Q
What is the standard enthalpy change of formation for elements not in a compounds
A
0Kjmol-1
14
Q
What is the specific heat capacity of a substance
A
- energy required to raie the temperature of 1g of a substance by 1K
15
Q
What is the specific heat capacity of water
A
- 4.18Jg-1K-1
