Chemistry (Winter Exam 2024)

Question 1

What is a Brønsted-Lowry acid?

Answer 1

A Brønsted-Lowry acid is a substance that donates a proton (H+) to another substance.

Question 2

True or False: A Brønsted-Lowry base is defined as a proton donor.

Answer 2

False: A Brønsted-Lowry base is defined as a proton acceptor.

Question 3

Which of the following is a characteristic of Brønsted-Lowry acids? (A) They accept electrons (B) They donate protons (C) They produce hydroxide ions

Answer 3

B) They donate protons

Question 4

What is work? What is the equation?

Answer 4

The energy require to move against a force.
W= -P delta V, or -delta nRT.

Question 5

When work is positive, what is true?

Answer 5

Work is done on the system by the surroundings.

Question 6

∆𝑛𝑔𝑎𝑠 = 𝑛𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠, 𝑔𝑎𝑠 − 𝑛𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠, 𝑔𝑎𝑠. For what concept does this equation apply?

Answer 6

Work - is the n total positive or negative?

Question 7

What is the equation for U?

Answer 7

∆U = q + w = –∆Usurr

Question 8

What is the reaction for the heat of a bomb calorimeter? Under what conditions does this happen?

Answer 8

Q cal = C cal ∆T, constant volume

Question 9

Q is equal to

Answer 9

Q = mc ∆ T

Question 10

What are the 2 equations for enthalpy (thermo)?

Answer 10

H = U + PV, or ∆H = ∆U + ∆n (gases) RT

Question 11

what is the equation for the enthalpy of reaction?

Answer 11

∆rH° = sum of
n∆𝑓H° 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 − sum of
n∆𝑓H°(𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠)

Question 12

how to calculate enthalpy of reaction from bond enthalpy?

Answer 12

H = sum of bond energies of reactants - sum of bond energy of products

Question 13

Salts dissolve in water to form _____ solution

Answer 13

electrolyte

Question 14

Solubility is the __________ of salt that can be achieved

Answer 14

max. concentration

Question 15

how is k calculated?

Answer 15

[products]^n/[reactants]^n

Question 16

in a k equation, n moles of gas is replaced by _____

Answer 16

partial pressure of that gas

Question 17

K reverse = ______

Answer 17

1/K forwards

Question 18

how to calculate q? what is q?

Answer 18

same as k. is the reaction quoteint: is the system at equilibrium? when it is, q = k. If Q<K, the reaction proceeds forward to reach equilibrium

Question 19

describe le chatelier’s principle

Answer 19

if a system at equilibrium is subjected to a change in concentration, pressure, volume, or temperature, the system will adjust itself to counteract the effect of the change and restore a new equilibrium

Question 20

how to calculate ksp?

Answer 20

ksp = [a (aq]^n][b (aq)^n]

Question 21

define Brønsted-Lowry definition of acids and bases

Answer 21

acid: proton (H+) donor
base: proton (H+) acceptor

Question 22

what is an amphoteric substance? give an example.

Answer 22

can behave as either and acid or a base. eg. water

Question 23

define a conjugate acid or base

Answer 23

Conjugate Acid: The species formed when a base gains a proton (H+)
Conjugate Base: The species formed when an acid loses a proton (H+)

Question 24

name the seven strong acids

Answer 24

Hydrobromic (HBr), Hydrochloric (HCl), Hydroiodic (HI), Nitric (HNO3), Sulphuric (H2SO4), Chloric (HClO3), Perchloric (HClO4)

Question 25

pH is equal to ______

Answer 25

-log[H3O+] or -log[H+]

Question 26

how to calculate percent ionization?

Answer 26

[concentration of ion]/[concentration of initial acid] x 100

Question 27

how to check if the 'very small x' assumption is valid?

Answer 27

x (from ice table)/initial acid concentration. if <5%, assumption is valid.

Question 28

how to find pH from pOH

Answer 28

subtract from 14

Question 29

how to calculate pOH

Answer 29

-log[OH]

Question 30

how to determine pkb, given pkw and pka? (conjugate acid/base pair)

Answer 30

𝑝𝐾𝑤 = 𝑝𝐾𝑎 + 𝑝𝐾𝑏 = 14.0

Question 31

how to calculate 𝑝𝐾𝑎? what does it mean? when is it strongest?

Answer 31

-log(𝐾𝑎). how strong an acid is; how tight is holds onto proton. smaller is stronger!

Question 32

Ka x Kb = Kw = 10^−14. what do we know about the strength of an acid/base?

Answer 32

higher the Ka/Kb (>1), stronger acid/base. lower the Ka/Kb (<1), weaker the acid/base.

Question 33

what is a Ka/Kb? what does it mean?

Answer 33

dissociation constant . larger it is, the more readily a substance dissociates COMPLETELY into ions.

Question 34

how to fine the W and P of a system (entropy)? Assume N is no. of molecules. what are W and P?

Answer 34

W = 2^N = number of possible states P = (1/2)^N = probability of system reverting to initial state

Question 35

what is entropy?

Answer 35

measure of how energy of a system is dispersed among available energy levels

Question 36

how to calculate entropy when heat is flowing?

Answer 36

∆𝑆 = 𝑞/𝑇 where q is the heat flow into the system

Question 37

define and describe the boltzmann formula

Answer 37

S = Kb ln W, where Kb is the boltzmann constant (1.3806 x 10^-23) and W is number of microstates (2^N)

Question 38

molar entropy increases with ___________ and _______________.

Answer 38

number of electrons, molar mass

Question 39

how to calculate entropy of reaction?

Answer 39

S = [n x sum of entropy of products] - [n x sum of entropy of reactants]

Question 40

how to calculate entropy from change in moles of gas?

Answer 40

if n<0, entropy is negative. if n>0, entropy is positive. can determine scale based on if work is done to system.

Question 41

what needs to happen for a spontaneous change?

Answer 41

ΔSuniv = ΔSsys + ΔSsurr > 0

Question 42

how to find change of entropy in surroundings?

Answer 42

ΔS (surroundings) = (ΔH system/T)

Question 43

what is the equation for gibbs energy (G)?

Answer 43

ΔG = ΔH − TΔS, where H is enthalpy, T is temperature and S is entropy.

Question 44

what is the criterion for spontaneous change, in terms of gibbs energy?

Answer 44

ΔG = - TΔS (universe). Negative change in Gibbs energy.

Question 45

how to calculate gibbs energy of reaction using gibbs energies of formation?

Answer 45

∆𝐺𝑟𝑥𝑛° = sum of ∆n𝐺𝑓(products) - sum of ∆n𝐺𝑓(reactants)

Question 46

how to calculate crossover temperature?

Answer 46

𝑇𝑐𝑟𝑜𝑠𝑠 = ∆𝐻°/∆𝑆°

Question 47

give the equation for gibbs free energy at equilibrium

Answer 47

ΔG° = -RT ln K

Question 48

give the equation for gibbs free energy under non-standard conditions

Answer 48

ΔG = -RT ln K + RT ln Q , or ∆𝐺 = 𝑅𝑇𝑙𝑛 𝑄/𝐾

Question 49

Lewis acids ______. Lewis bases ______.

Answer 49

accept electrons, donate electrons

Question 50

what are arrhenius acids? arrhenius bases?

Answer 50

acids: dissociate to form H+ in water bases: dissociate to form OH- in water

Question 51

what types of conjugate bases are made when weak acids dissociate? what about strong acids?

Answer 51

When weak acids dissociate, they form strong conjugate bases. When strong acids dissociate, they form weak conjugate bases.

Question 52

cations are ______. anions are _________.

Answer 52

reduced, oxidized.

Question 53

for a galvanic cell with copper as an anode (0.3M solution) and silver as a cathode (1M solution), write the symbolic notation

Answer 53

Cu(s) |Cu2+(aq, 0.3 M) ║ Ag+(aq, 1 M) |Ag(s)

Question 54

how to calculate standard cell potential?

Answer 54

E°cell = E°(cathode) – E°(anode)

Question 54

in a reduction half reaction, the ________ is an oxidizing agent and the ________ is a reducing agent

Answer 54

reactant, product

Question 54

which side is the cathode on? the anode?

Answer 54

Cathode is on the right. anode is on the left.

Question 54

when E°cell > 0, the process is ___________.

Answer 54

spontaneous

Question 55

species with a higher E° are more easily ______, whereas species with a lower E° are more easily _______.

Answer 55

reduced, oxidized

Question 56

E°cell equation at equilibrium, nonstandard conditions (Nernst eq.)

Answer 56

Ecell = E°cell - (RT/zF) ln Q R is gas constant, z is number of electrons transferred, F is faraday constant, Q is reaction quotient.

Question 57

E°cell at standard conditions and equilibrium (equation)

Answer 57

E°cell = (RT/zF) ln K

Question 58

how do concentration cells function?

Answer 58

identical electrodes (E°cell = 0), voltage possible due to differences in ion concentration

Question 59

what is the equation for Ecell of a concentration cell?

Answer 59

Ecell = E°cell - (RT/zF) ln ([H+ anode]/[H+ cathode])

Question 60

What is the relation between pH and pKa?

Answer 60

pH = pKa + log ([conjugate Base]/[weak Acid])

Question 61

What is the relationship between pH and pKb?

Answer 61

pH = pKb + log([conjugate acid]/[weak base])

Question 62

For a heat of fusion question, how do we find q?

Answer 62

Q = (m)(Hfus)

Question 63

What is mass equal to? How can we substitute mass in an enthalpy problem (specifically heat of fusion)?

Answer 63

m = (v)(density), therefore q = (v)(density)(heat of fusion)

Question 64

What are qp and qv? How are they calculated?

Answer 64

Q at constant pressure/volume. Qp = delta H (delta U + P delta V) Qv = delta U (q - W)

Question 65

How to calculate change in ENTROPY during a phase change?

Answer 65

S = delta H/T

Question 66

What’s the difference between E°cell and Ecell?

Answer 66

E°cell is under standard conditions, Ecell is non-standard

Question 67

How does Kb relate to Ka?

Answer 67

Kw = Ka x Kb = 1.0 x 10^-14

Question 68

Name six main oxidation rules

Answer 68

1. Oxygen is almost always -2 2. Group 1 elements are +1, group two elements are +2 3. Fluorine is -1 4. Hydrogen is +1 with nonmetals 5. Hydrogen is -1 with metals (and boron)