Energy Changes

Question 1

What does ‘Q’ stand for in the energy change equation?

Answer 1

Energy change (in Joules)

Question 2

What does ‘m’ stand for in the energy change equation?

Answer 2

Mass OF THE SOLUTION (where 1cm3 = 1g)

Question 3

What does ‘c’ stand for in the energy change equation?

Answer 3

Specific heat capacity (always 4.18)

Question 4

What does ‘delta T’ stand for in the energy change equation?

Answer 4

Change in temperature (*C)

Question 5

What is the equation for energy change?

Answer 5

Q = m x c x delta T

Question 6

What is the symbol for enthalpy change?

Answer 6

Delta H

Question 7

What is the equation for molar enthalpy change?

Answer 7

Delta H = Q / Moles

Question 8

What is the equation for moles used in enthalpy calculations?

Answer 8

Moles = Concentration x Volume / 1000
OR
Moles = Mass / Mr

Question 9

What are the steps for calculating enthalpy change?

Answer 9

1. Find the energy change for the reaction
2. Find the moles of the fuel
3. Find the enthalpy change (delta H)

Question 10

What is an exothermic reaction?

Answer 10

One that releases energy.

Question 11

What is an endothermic reaction?

Answer 11

One that takes in energy.

Question 12

In an energy level diagram, if the products are lower in energy than the reactants, the reaction is…

Answer 12

Exothermic

Question 13

In an energy level diagram, if the products are higher in energy than the reactants, the reaction is…

Answer 13

Endothermic

Question 14

If delta H is positive, the reaction is…

Answer 14

Endothermic

Question 15

If delta H in negative, the reaction is…

Answer 15

Exothermic

Question 16

Is the breaking of bonds exothermic or endothermic?

Answer 16

Endothermic (it requires energy to happen)

Question 17

Is the making of bonds exothermic or endothermic?

Answer 17

Exothermic

Question 18

To calculate energy change per mole using bond energies, you…

Answer 18

Take away the bonds formed in the products from the bonds broken in the reactants.