Key Terms

Question 1

Electron Configuration Order

Answer 1

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6

Question 2

Why does 4s2 come before 3d10?

Answer 2

Electrons fill low energy orbitals (closer to the nucleus) before they fill higher energy ones. Where there is a choice between orbitals of equal energy, they fill the orbitals singly as far as possible.

Question 3

When adding electrons for anions

Answer 3

you add them as usually you would do for electron configuration

Question 4

When removing electrons for cations

Answer 4

you remove them not from the END of the electron configuration but you always remove electrons from the shell that is furthest away from the nucleus. When removing electrons, they are taken away from the 4s orbital first as it is further away from the nucleus, and then electrons are removed from the 3d orbital.

Question 5

Which two atoms are exceptions to the rule when it comes to electron configurations?

Answer 5

Chromium (Cr), copper (Cu)

Question 6

Why are Chromium and Copper exceptions to the electron configuration rules?

Answer 6

A sub-level which is exactly half-filled is more stable than a partially filled sub-level which is not half full. In both examples, an electron moves from the 4s sublevel to produce a 1/2 full 3d (Cr) or completely filled 3d (Cu). This gives the atom greater stability.

Question 7

What is electronegativity?

Answer 7

The tendency of an atom to attract a bonding pair of electrons

Question 8

Define first ionization energy

Answer 8

How much energy is needed to remove 1 mole of electrons from 1 mole of gaseous atoms.

Question 9

What is Δ_cH^o ?

Answer 9

Standard enthalpy of combustion - enthalpy change during complete combustion of 1 mole of a substance in its standard state

Question 10

What is Δ_fH ^o ?

Answer 10

formation - enthalpy change when 1 mole of a compound is formed from its constituent elements

Question 11

What is ΔfusH ^o ?

Answer 11

fusion - the amount of heat energy required to change 1 mole of a solid to 1 mole of a liquid at the melting point

Question 12

What is ΔsubH^o ?

Answer 12

sublimation - heat energy required to change 1 mole of a substance from a solid to gas (without changing to liquid first)

Question 13

What is ΔvapH ^o ?

Answer 13

Vaporisation - amount of heat energy required to change 1 mole of a substance from a liquid to gas at the boiling point

Question 14

What is Entropy?

Answer 14

the measure of how much and how widely energy has been dispersed in a system.

Question 15

When thinking about enthalpy, what must you consider?

Answer 15

Solid to liquid or liquid to gas.

Question 16

Liquid to gas, what usually happens to the overall entropy?

Answer 16

System

The entropy of the system will increase as gas particles are more disordered than liquid particles.

Surroundings

the enthalpy of the surroundings decreases as the liquid evaporates as energy is absorbed from the surroundings to break the intermolecular forces between the liquid molecules.

Therefore the entropy of the surroundings decreases.

Overall

So the overall entropy decreases.

Question 17

Gas to liquid, what happens to the overall entropy?

Answer 17

System

The particles in the gas lose energy which causes a decrease in entropy.

surroundings

The particles in the surroundings gain energy. The energy is distributed over a much larger volume, and there is hardly any rise in temperature which results in an increase in entropy. The surrounding particles become more disordered.

overall

The overall result for the system and surroundings is a net increase in entropy, so heat will flow from the system to the surroundings.

Question 18

How and why does enthalpy change when you make bonds?

Answer 18

energy is released when new bonds form. Bond-making is an exothermic process.

Energy released is more than the energy absorbed

Question 19

How and why does enthalpy change when you break bonds?

Answer 19

Energy is absorbed to break bonds. Bond-breaking is an endothermic process.

Energy absorbed is more than the energy released.

Question 20

Endothermic reactions are only spontaneous if…

Answer 20

the increase in entropy is greater than the change in temperature of the surroundings.

The effect of entropy has to be greater.

Question 21

What is the formula for calculating heat energy in calorimetry? What do all of the letters stand for?

Question 22

What is the specific heat capacity of water?

Question 23

What are the units of q?

Question 24

How do you go from q to ΔH^o? What’s the formula (and units)?

Question 25

What happens to the overall entropy if the reaction is exothermic?

Answer 25

If the reaction is exothermic, the surroundings will increase in entropy, as heat is being released to the surroundings, creating more disorder/dispersal