enthalpy

Question 1

what is enthalpy change?

Answer 1

the energy change at constant pressure in a reaction

Question 2

what is activation energy?

Answer 2

the minimum energy required for the reaction to take place

Question 3

what are the standard conditions?

Answer 3

1. 100kPa
2. 1 moldm-3 concentration of solutions
3. 298 K

Question 4

what is the enthalpy change of reaction?

Answer 4

change with a reaction in the molar quantities shown in the equation under standard conditions

Question 5

what is the enthalpy change of formation?

Answer 5

change that takes place when 1 mole of a compound is formed from its elements under standard conditions

Question 6

what is the enthalpy change of combustion?

Answer 6

when 1 mole of a substance react completely with oxygen under standard conditions

Question 7

what is the enthalpy change of neutralisation?

Answer 7

change that forms 1 mole of water under standard conditions

Question 8

what is the equation for the enthalpy change?

Answer 8

q = mcDeltaT

Question 9

what does average bond enthalpy mean?

Answer 9

the enthalpy change, in gaseous molecules, when 1 mole of bonds is broken

Question 10

what is an exothermic reaction in terms of chemical bonds?

Answer 10

more energy was transferred away forming bonds than taken in to break them

Question 11

what is Hess’ Law?

Answer 11

enables the calculation of an enthalpy change when not possible to measure it directly
arrows up for formation, down for combustion

Question 12

what is the important thing when doing Hess calculations?

Answer 12

use the data given, not necessarily in the question