Topic 7: Thermo Chemistry

Question 1

What is ΔH?

Answer 1

Change in Enthalpy.

Question 2

What is an exothermic reaction?

Answer 2

Exothermic reactions transfer energy to the surroundings.

Question 3

What is an endothermic reaction?

Answer 3

Endothermic reactions take energy in from the surroundings.

Question 4

How do you know if the reaction is exothermic or endothermic?

Answer 4

If there is -ΔH the reaction is exothermic.

If there is +ΔH the reaction is endothermic.

Question 5

How to draw an energy level diagram?

Answer 5

LOOK IN BOOK.

Question 6

Burning Alcohols experiment?

Answer 6

LOOK IN BOOK

Question 7

Alcohols equation?

Answer 7

(alcohol) + oxygen = carbon dioxide + water

Question 8

Burning Alcohol experiment, calculations?

Answer 8

• Write word equation
• Write symbol equation and structure
• Calculate Bonds broken by looking at sheet
• Calculate Bonds made
• Find the difference
• Draw graph

Question 9

The trend in the Burning Alcohol experiment?

Answer 9

The greater the Mr of the alcohol the more energy was transformed per gram of fuel.

Question 10

To make new chemicals we need to….

Answer 10

Break bonds.

Question 11

When we make new substances we need to break bonds and …..

Answer 11

Make new ones.

Question 12

What is bond energy?

Answer 12

The energy that is needed to break chemical bonds.

Question 13

The units for ΔH?

Answer 13

kJmol-1

Question 14

Thermo Chemistry Enthalpy questions EXAMPLES?

Answer 14

LOOK IN BOOK

Question 15

Method for Calorimeter burning fuels?

Answer 15

• Set up apparatus
• Weigh spirit burner
• Light burner and wait until the water temperature has risen by 15-20oC - Then put out the burner.
• Repeat with other alcohols

Question 16

General Symbol equation for a Alcohol?

Answer 16

CnH2n+1OH

Question 17

General Symbol equation for an Alkane?

Answer 17

CnH2n+2

Question 18

General Symbol equation for an Alkene?

Answer 18

CnH2n

Question 19

Equation for moles?

Answer 19

moles = mass / Mr

Question 20

Equation for Mass?

Answer 20

mass = Mr x moles

Question 21

Energy transferred to water =

Answer 21

mass x specific heat capacity x temp change

Question 22

If the ΔH goes down?

Answer 22

The answer is negative and exothermic.

Question 23

If the ΔH goes up?

Answer 23

The answer is positive and endothermic.

Question 24

What is thermal decomposition?

Answer 24

Mostly used for making CO2 in the lab by heating metal carbonates.

Question 25

Equation for thermal decomposition?

Answer 25

Metal carbonate -Heat-> Metal Oxide + CO2

Question 26

Thermal decomposition of Magnesium Carbonate?

Answer 26

MgCO3 -> MgO + CO2