chapter 9

Question 1

what is enthalpy?

Answer 1

measure of heat energy present in a chemical system

Question 2

what is enthalpy change?

Answer 2

amount of energy released/taken in during a chemical reaction

Question 3

what are the standard conditions?

Answer 3

1 atmosphere (100kPa)
298K (25 degrees)
1 mold dm cubed

Question 4

what does it mean if an element is in its standard state?

Answer 4

its physical state of a substance under standard conditions

Question 5

what is the standard enthalpy change for a reaction (r)?

Answer 5

enthalpy change that accompanies a reaction in the molar quantities shown in a chemical reaction under standard conditions

Question 6

what is the standard enthalpy change of combustion (c)?

Answer 6

enthalpy change that occurs when 1 mole of a substance is burned completely in oxygen under standard conditions

Question 7

what is the standard enthalpy change of formation (f)?

Answer 7

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

Question 8

what is the standard enthalpy change of neutralisation (neut)?

Answer 8

enthalpy change that accompanies the reaction of an acid by a base to form 1 mole of H2O under standard conditions

Question 9

what is the equation for energy transferred (q)?

Answer 9

q = mc change T
IN JOULES

Question 10

how do you calculate enthalpy change?

Answer 10

calculate q (energy transferred)
calculate moles of fuel burned (excess)
q/moles

Question 11

what is hess’ law?

Answer 11

shows that enthalpy change is independent to route

Question 12

what do you do when you have combustion data for an enthalpy cycle?

Answer 12

use the combustion data
arrows go DOWN to CO2 and H2O
you are finding out the enthalpy change of formation

Question 13

what do you do when you have formation data for an enthalpy cycle?

Answer 13

use the formation data
arrows UP
elements at the bottom
you are finding out the enthalpy change of combustion