Module 3: Periodic Table and Energy

Question 1

Is energy taken in or given out when making new bonds?

Answer 1

Energy is taken in.

Question 2

Is energy taken in or given out when breaking bonds?

Answer 2

Energy is released.

Question 3

What are standard conditions?

Answer 3

101kPa and 298K

Question 4

What is Standard Enthalpy Change of Reaction?

Answer 4

The enthalpy change when the molar quantities of the substances shown in the equation as written react, under standard conditions.

Question 5

What is Standard Enthalpy Change of Combustion?

Answer 5

The enthalpy change when one mole of an element or a compound reacts completely with oxygen under standard conditions.

Question 6

What is Standard Enthalpy Change of Formation?

Answer 6

The enthalpy change when one mole of a compound is formed from its elements under standard conditions.

Question 7

What is Standard Enthalpy Change of Neutralisation?

Answer 7

The enthalpy change when an acid and an alkali react to form one mole of water under standard conditions.

Question 8

What is bond enthalpy?

Answer 8

The enthalpy change when breaking 1 mole of a given bond in the molecules of a gaseous species.

Question 9

What is the effect of temperature change?

Answer 9

Increases the kinetic energy of particles making them faster, increasing the frequency of collisions. More molecules have energy greater than or equal to activation energy.

Question 10

How does temperature change affect Boltzmann’s distribution curve?

Answer 10

• Area under the curve does not change
• The curve peaks further out and shifts to the right
• Average energy of all particles has increased
• Proportion of molecules with energy greater than or equal to activation energy has increased, number of successful collisions increases
• Rate of reaction increases.

Question 11

What is a heterogenous catalyst?

Answer 11

A catalyst that has a different state to the reactants.

Question 12

What is a homogenous catalyst?

Answer 12

A catalyst that has the same state as the reactants.

Question 13

How do catalysts work?

Answer 13

A catalyst provides an alternate reaction pathway which has a lower activation energy.

Question 14

Rules of a dynamic equilibrium system?

Answer 14

• The rate of the forward reaction is equal to the rate of the backward reaction
• The concentration of reactants and products do not change

Question 15

How do catalysts help in industry?

Answer 15

They provide an alternate reaction pathway for lower energy so:
* Energy demand is reduced
* Less CO₂ emissions from the burning of fossil fuels

Question 16

What will an increase in pressure favour?

Answer 16

The reaction where there is a decrease in the number of gaseous molecules.

Question 17

What will a decrease in pressure favour?

Answer 17

The reaction where there is an increase in molecules.

Question 18

What must you include if Le Chateliers principle is mentioned?

Answer 18

Minimise the change.

Question 19

How does a catalyst affect dynamic equilibrium?

Answer 19

It increases the rate at which equilibrium is attained and has no effect on position of equilibrium.

Question 20

What does K_c describe?

Answer 20

The actual position of equilibrium.

Question 21

K_c formula?

Answer 21

products/reactants

Question 22

If Kc value is less than 1 where does PoE lie?

Answer 22

Left

Question 23

If Kc value is greater than 1 where does PoE lie?

Answer 23

To the right.

Question 24

What is the term used to describe repeating patterns in the Periodic Table?

Answer 24

Periodicity.

Question 25

Whats special about Group 2 elements?

Answer 25

They are strong reducing agents as they donate 2 electrons which reduce the other species.

Question 26

Calcium + Nitric Acid half equations?

Answer 26

Ca –> Ca²⁺ + 2e^-

2H⁺ + 2e^- –> H₂

Question 27

Does reactivity of Halogens increase or decrease as you go down the group?

Answer 27

Decrease.

Question 28

Trend in Halogen displacements?

Answer 28

A more reactive Halogen will displace a less reactive Halogen from a solution of its halide ion. E.g chlorine can displace bromine and iodine

Question 29

What is a disproportionation reaction?

Answer 29

A reaction where an element is simultaneously oxidised and reduced.

Question 30

Example of disproportionation reaction?
Chlorine + Water

Answer 30

Cl_2(aq) + H₂O_(l) –> HOCl_(aq) + HCl_(aq)

Question 31

What is the test for Halide ions?

Answer 31

Add silver nitrate if halide is present a coloured precipitate will form:
* Chlorine - cloudy white ppt
* Bromine - cream ppt
* Iodine - yellow ppt

Question 32

Full and ionic equations for Halide ions and silver nitrate?

Answer 32

KCl_(aq) + AgNO_3(aq) –> AgCl_(s) + KNO_3(aq)

Cl^- _(aq) + Ag⁺ _(aq) –> AgCl_(s)

Question 33

How to test for carbonate ions?

Answer 33

Add dilute acid such as nitric acid, positive result is fizzing.

Question 34

How to test for sulfate ions?

Answer 34

Add Ba²⁺ in the form of BaCl₂ will create cloudy white ppt if present.

Question 35

What is the order to find out anions?

Answer 35

carbonate then sulfate then halide, this eliminates possibility of false result by removing the ions in each step.

Question 36

How to test for ammonium?

Answer 36

warm with NaOH will turn litmus paper blue and make ammonia gas.

Question 37

Another example of disproportionation reaction?
Chlorine + Sodium hydroxide

Answer 37

Cl_2(g)+ 2NaOH_(aq) —> NaCl_(aq) + NaClO_(aq)+ H₂O_(l)