(A3) Energy Changes in Industry

Question 1

Celsius to Kelvin

Answer 1

°C + 273 = K

Question 2

What is standard condition?

Answer 2

The condition of the environment need for experiments

Question 3

Standard Condition (Room Temperature)

Answer 3

298K

Question 4

Standard Condition (Pressure)

Answer 4

100 Kpa or 1 atm

Question 5

What is activation energy?

Answer 5

Activation energy is the minimum amount of energy required by reactants to form products

Question 6

What happens in the reaction profile of an exothermic reaction?

Answer 6

The energy of the products is lower than the energy of the reactants because energy is released

Question 7

What happens in the reaction profile of an endothermic reaction?

Answer 7

The energy of the products is higher than the energy of the reactants because energy is be taken in

Question 8

What is exothermic?

Answer 8

Bond making

Question 9

What is endothermic?

Answer 9

Bond breaking

Question 10

Is the enthalpy of an endothermic reaction positive or negative?

Answer 10

Positive

Question 11

Is the enthalpy of an exothermic reaction positive or negative?

Answer 11

Negative

Question 12

Why is the enthalpy of an exothermic reaction positive?

Answer 12

Energy is released from the reaction when a bond is made

Question 13

Why is the enthalpy of an endothermic reaction postive?

Answer 13

Where energy is taken in from the surroundings to break a bond

Question 14

What is the system?

Answer 14

Where the reaction is occurring

Question 15

What is the surroundings?

Answer 15

Where the energy of the reaction can transfer to?

Question 16

What halogens are a gas?

Answer 16

F₂ and CL₂

Question 17

What halogens are a liquid?

Answer 17

Br₂

Question 18

What halogens are a solid?

Answer 18

I₂

Question 19

What is enthalpy?

Answer 19

The thermal energy stored in a chemical system

Question 20

How can enthalpy be measured?

Answer 20

If the temperature of a reaction has changed

Question 21

Enthalpy Change Equations

Answer 21

Enthalpy Change = Enthalpy taken in - enthalpy taken out

Enthalpy Change = Enthalpy to break bonds - Enthalpy to make bonds

Enthalpy Change = Enthalpy of reactants - Enthalpy of products

Question 22

What is necessary for any reaction to happen

Answer 22

Bonds must be broken in reactants
Bonds must be made in products

Question 23

Enthalpy Equation

Answer 23

H = U + PV

Question 24

What happens to the enthalpy as we go down a group?

Answer 24

The reaction becomes less exothermic

Question 25

Why does the reaction get less exothermic as we go down a group?

Answer 25

Because the size of the ion gets bigger so less energy is released when bonds forms

Question 26

What happens to the enthalpy when the charge of the metal ion increases?

Answer 26

The reaction becomes more exothermic

Question 27

Why does the reaction get more exothermic as the charge of the metal ion increases?

Answer 27

Because the metal ion gets smaller due to the increased charge.
The increased charge causes the attraction to become stronger and more energy is released when bonds form.

Question 28

What happens to the enthalpy as we go across a period?

Answer 28

• The charge of the ion increases, attraction becomes stronger so the ion becomes smaller
• The reaction become more exothermic so more energy so released when bonds are formed

Question 29

What is the enthalpy of formation?

Answer 29

Enthalpy change when one mole of a substance is formed from all its elements in its standard state

Question 30

Example equation of enthalpy of formation

Answer 30

2 Na (s) + ¹/²O₂(g) –> Na₂O (s)

Question 31

What is the enthalpy of combustion?

Answer 31

Enthalpy change when one mole of a substance undergoes complete combustion with all its substances in their standard state

Question 32

Example equation of enthalpy of combustion

Answer 32

H₂ (g) + ¹/²O₂(g) –> H₂O (l)

Question 33

What is the enthalpy of hydration?

Answer 33

Enthalpy change when one mole of gaseous ions become hydrated

Question 34

Example equation of enthalpy of hydration

Answer 34

Mg²⁺ (g) + aq –> Mg²⁺ (aq)