Chemistry Video 15

Question 1

Zeroth Law of thermodynamics

Answer 1

Deals with thermal equilibrium. Describes a situation where there is no net heat flow between 2 systems. If 2 systems are in thermal equilibrium with a third system, then they are also in thermal equilibrium with each other

Question 2

First Law of thermodynamics

Answer 2

Conservation of energy

Question 3

Entropy

Answer 3

The partial loss of a heat engine’s ability to do work. State function measured in J/K. Symbol is S

Question 4

Change in entropy

Answer 4

Heat over the Kelvin temperature for a reversible process. Q / T.

Question 5

Second law of thermodynamics

Answer 5

The change in entropy of the universe for any spontaneous process is greater than 0. The entropy of the universe must increase for any spontaneous process.

Question 6

Microstate

Answer 6

A specific configuration of all the particles and energies in a system. The dispersal of matter and energy tends to be spontaneous. Things move to more disorder. S = klnW, where k is the Boltzmann constant 1.38*10^(-23) m^2 kg/s^2 K. W is the number of microstates. The distribution with the greatest number of microstates will be preferred statistically

Question 7

When change in entropy is a positive value

Answer 7

Increase in entropy, entropically favourable. More likely to be spontaneous.

Question 8

When change in entropy is a negative value

Answer 8

Decrease in entropy, entropically unfavourable. More likely to be non-spontaneous.

Question 9

Third law of thermodynamics

Answer 9

At absolute zero (0 K) everything would be a solid. The entropy of any crystalline substance at absolute zero is equal to zero. It is impossible to lower the temperature of any system to absolute zero in a finite number of steps.

Question 10

Gibbs Free Energy, G

Answer 10

Determines spontaneity. deltaG = deltaH – T*deltaS

Question 11

Negative deltaG

Answer 11

spontaneous

Question 12

Positive deltaG

Answer 12

non-spontaneous

Question 13

deltaG = 0

Answer 13

equilibrium

Question 14

Standard change in free energy

Answer 14

For equilibrium:
(standard change in free energy) = -(R)(T)(lnK)

Not equilibrium and Q is reaction quotient:
(change in free energy) = (standard change in free energy) + (R)(T)(lnQ)

Question 15

Standard change in free energy is negative and K > 1

Answer 15

Products favoured (spontaneous)

Question 16

Standard change in free energy is positive and K < 1

Answer 16

Reactants favoured (non-spontaneous)

Question 17

Standard change in free energy is 0 and K = 0

Answer 17

Reactants and products favoured equally

Question 18

From Gibbs Free Energy Equation, delta H is negative and delta S is positive

Answer 18

deltaG is always negative, meaning spontaneous.

Question 19

From Gibbs Free Energy Equation, delta H is positive and delta S is negative

Answer 19

deltaG is always positive, meaning non-spontaneous.

Question 20

From Gibbs Free Energy Equation, delta H is positive and delta S is positive

Answer 20

deltaG is spontaneous at high T and non-spontaneous at low T.

Question 21

From Gibbs Free Energy Equation, delta H is negative and delta S is negative

Answer 21

deltaG is spontaneous at low T and non-spontaneous at high T.

Question 22

Electric charge

Answer 22

Measured in Coulombs

Question 23

Electric current

Answer 23

Rate of charge flow carried by electrons or ions. Measured in amperes where 1A = 1 C/s. Always flows in a path called a circuit.

Question 24

Electric potential

Answer 24

Ability of an electric field to do work (move charges). Measured in volts where 1V = 1 J/C

Question 25

Electric field

Answer 25

Generated by particles with electric charge

Question 26

Electrochemistry

Answer 26

Involves REDOX reactions.

Question 27

Galvanic Cell (AKA voltaic)

Answer 27

Electrochemical cell. Spontaneous REDOX reaction generates an electric current. Each beaker is called a half cell and each half cell has a metal electrode. Oxidation occurs at anode. Reduction occurs at cathode. Half cells are connected by salt bridge that maintains charge balance and by a wire connected to voltmeter. Electrons always go from anode to cathode.

Question 28

Cell notation

Answer 28

From left to right: list the material in the anode, then put vertical line ( | ) to show phase boundary, then put anode solution including concentration, then put double vertical line ( || ) to represent the separation between the 2 half cells, then put cathode solution including concentration, then put vertical line ( | ) to show phase boundary, list the material in the cathode. Spectator ions not listed. Half reactions have coefficients of 1. Anode always on the left side.

Question 29

Standard hydrogen electrode

Answer 29

Used as a reference to list reduction potentials for all substances. This is a platinum electrode sitting in 1 molar hydrochloric acid that facilitates reduction of H+ ions into H2 gas, which has a standard reduction potential of 0 V.

Question 30

Cell potential (E cell)

Answer 30

E cell = E cathode – E anode. When looking at standard reduction potentials of 2 half cells, the half cell reaction with the greater (more positive) reduction potential is the reduction half-reaction, which is the cathode. We do not need to alter the reduction potentials in the list of reduction potentials to calculate E cell.

Question 31

Primary batteries

Answer 31

Single-use batteries that cannot be recharged. i.e. zinc dry cell, alkaline battery, zinc-carbon battery

Question 32

Secondary batteries

Answer 32

Multiple-use batteries that can be recharged. i.e. in phones, cars, nickel-cadmium battery, lithium-ion battery, lead acid battery

Question 33

Fuel cells

Answer 33

Converts chemical energy into electrical energy. For satellites, boats, submarines. Requires continuous source of fuel. Utilize the splitting of hydrogen atoms to produce fuel. The process involves splitting hydrogen into electrons and protons, allowing the
components to run through the battery to produce electricity, and finally combining the
reactants with oxygen to produce water as a byproduct.

Question 34

Electrolytic cell

Answer 34

An electric current drives a nonspontaneous REDOX reaction. i.e. Electrolysis of water. Electrolysis of aqueous sodium chloride.

Question 35

Calculate total charge

Answer 35

Current is measured in Amperes. Total charge is Q. Q = It = nF. Q is the total charge in C, I is the current in C/s and t is time in seconds. n is moles of electrons transferred and F is Faraday’s constant of 96485 C/mol.

Question 36

Equation with Ecell and deltaG

Answer 36

Standard deltaG = -(n)(F)(Ecell)