Unit 1: Thermodynamics

Question 1

Thermochemistry

Answer 1

Study of energy changes.

Question 2

Physical change

Answer 2

a change in a substances form.

Question 3

Chemical change

Answer 3

Rearrangement of atoms to form new compounds.

Question 4

Nuclear change

Answer 4

Change in protons/neutrons that results in the formation of new atoms.

Question 5

Potential E

Answer 5

Energy stored in a object.

Question 6

Kinetic E

Answer 6

Energy of motion.

Question 7

Work

Answer 7

Force acting over a distance

Question 8

Heat

Answer 8

Amount of thermal energy transferred between systems cuz of a temperature difference.

Question 9

Endothermic

Answer 9

Energy is absorbed, temperature of surrounding environment lowers.

Question 10

Exothermic

Answer 10

Energy is released, temperature of surrounding environment increases.

Question 11

1st Law:

Answer 11

Energy cant be created or destroyed, only transferred or transformed.

Question 12

2nd Law:

Answer 12

When 2 objects are in contact, heat is transferred from the hotter object to the cooler one until = same temperature.

Question 13

Open system:

Answer 13

E and matter can be exchanged w/surroundings.

Question 14

Closed system:

Answer 14

E but not matter can be exchanged w/surroundings.

Question 15

Isolated system:

Answer 15

E and matter cant be exchanged w/surroundings.

Question 16

Alpha decay:

Answer 16

Atom breaks down to 2p and 2n (mass decreases by 4 and atomic number decreases by 2) = new element.

Question 17

Beta Particle:

Answer 17

a fast electron emitted during radioactive decay of an atoms nucleus.

Question 18

Beta decay:

Answer 18

a neutron changes into a p and an e (the nucleus will have one less e but an extra p). Atomic number increases by 1, but mass stays same.

Question 19

Gamma Decay:

Answer 19

After radioactive decay, nucleus emits extra energy as gamma rays - electromagnetic radiation w/high frequency.

Question 20

Nucelar fusion:

Answer 20

when 2 light atoms fuse tg to create a heavier atom w/ the goal of generating E.

Question 21

Nucelar fission:

Answer 21

when a heavier nuclide splits into 2 or more pieces (releases E)

Question 22

Enthalpy (∆H):

Answer 22

Total E contained in a chemical system (PE & KE)

Question 23

Enthalpy of Solution:

Answer 23

1) bonds break b/t solutes and solvents so that attraction can occur. Change associated w/dissolving = ∆Hsolution

Question 24

Phase change and enthalpy:

Answer 24

Substance goes from more ordered to less ordered (s –> l) = Endothermic

Substance goes from less ordered to more ordered (l –> s) = Exothermic

Question 25

Enthalpy change of rxn (∆Hr):

Answer 25

When bonds in reactants break: requires E --> endothermic When bonds form to make products: releases E --> exothermic

Question 26

How to find Enthalpy

Answer 26

Using a calorimeter (double-walled vessel w/ a thermometer and stirring rod, filled w/H2O).

Question 27

Assumptions of calorimeter

Answer 27

1) thermal E exchange b/t materials in vessel and outside can be ignored 2) heat capacity of water applies to any new solutions made 3) occurs under constant P

Question 28

∆H˚r

Answer 28

Enthalpy change per mol for a reaction at SATP.

Question 29

Hess Law

Answer 29

Enthalpy change is dependent only on the initial and final conditions.

Question 30

Standard Molar Enthalpy of Formation: ΔH˚f

Answer 30

Amount of E absorbed/released when 1 mole of a compound is directly formed from its elements in there most stable state @ SATP.

Question 31

Rate of a chemical rxn:

Answer 31

The speed @ which the [C] of a reactant/product changes. Dependent on frequency of collisions and how many of the collision are successful.

Question 32

r = ?

Answer 32

Absolute value. Rate can be expressed as product formation or consumption.

Question 33

Average rate of Rxn:

Answer 33

Speed at which reaction proceeds over time. Decreases overtime.

Question 34

Instantaneous rate of Rxn:

Answer 34

Rate of rxn @ a particular point in time.

Question 35

Methods to measure rxn rates:

Answer 35

1) Produce a gas (gas collected --> volume can be quantified as rxn proceeds) 2) Measuring Mass (total mass will be lost is gas is produced) 3) Rxns w/ions (measure the change in conductivity and plot it w/time) 4) Colour change (measure the intensity of colour using a spectrometer)

Question 36

Collision theory

Answer 36

Chemical rxn always has particles that are moving @ diff speeds. Depends on the orientation and sufficent of Energy.

Question 37

Effective and ineffective collision:

Answer 37

Effective: when particles have high energy and proper orientation to make new bonds. Ineffective: when particles bounce off each-other.

Question 38

Transition state

Answer 38

Unstable structure formed during successful collisions b/t reactant particles. Always have a higher E lvl then prdts/rxnts.

Question 39

Activated Complex (Ea)

Answer 39

Minimum E required for the activation complex to form and a successful rxn to happen. Lower the Ea --> faster the rxn.

Question 40

Reaction Mechanism

Answer 40

Process by which a rxn occurs.

Question 41

Factors that affect the rates of a rxn:

Answer 41

1) [C]: Higher = higher rate of rxn cuz theres more particles --> more collisions. 2) Surface area: Large SA --> faster rxn since more area is available for the solid to collide. 3) Temp: Higher temps increase the KE (speed of particles) so more collisions happen. 4) Catalyst: Lower the activation E req so rate increases.

Question 42

Elementary step:

Answer 42

A step in a rxn mechanism that involves a single collision of 2-3 particles.

Question 43

Intermediates:

Answer 43

Compounds that are produced and consumed.

Question 44

Slowest elementary step:

Answer 44

Determines the rate of a rxn (rate determining step).

Question 45

Rate law:

Answer 45

determined experimentally and expresses the relationship of the rate of rxn to the rate constant (k) + [C] of reactants raised to a power.

Question 46

Rate order of 0:

Answer 46

[C] of rxnt doesn't affect the rate of rxn.

Question 47

Rate order of a negative integer:

Answer 47

[C] INVERSELY affects the rate of rxn.

Question 48

Rate of positive integer:

Answer 48

[C] DIRECTLY affects the rate of rxn.