Topic 6 Energetics

Question 1

What is the first Law of thermodynamics

Answer 1

During a chemical reaction, energy cannot be created or destroyed. However, one form of energy can be transferred into another form

Question 2

What is chemical energy made up of

Answer 2

kinetic energy and potential energy

Question 3

What is directly proportional to the absolute temperature of a substance

Answer 3

the heat energy of the substance

Question 4

What is the enthalpy change of a process

Answer 4

the heat energy that is transferred between the system and the surroundings at constant pressure

Question 5

What is an exothermic reaction

Answer 5

when heat energy is transferred from the system to the surroundings

Question 6

what is an endothermic reaction

Answer 6

when heat energy is transferred from the surroundings to the system

Question 7

what does a negative sign indicate

Answer 7

heat energy is transferred from the system to the surroundings. The reaction is exothermic

Question 8

what does a positive sign indicate

Answer 8

heat energy is transferred from the surroundings to the system

Question 9

What effect do exo and endo reactions have on temp

Answer 9

exo: increase
endo: decrease

Question 10

Define standard enthalpy change of reaction

Answer 10

the enthalpy change that occurs when equation quantities of materials react under certain conditions, which is 100 kpa and 298K

Question 11

How is the change in enthalpy found

Answer 11

H (products) ~ H (reactants)

Question 12

What is the standard enthalpy change of combustion

Answer 12

the enthalpy change measured at 100kPa and at a stated temperature, usually 298K, when one mole of a substance is completely burned in oxygen