TermTest1 1 - Aboutlearnfaster.ca/wp-content/uploads/Chem201-TT1... · Chem201 is 100 %...

Chemistry 201 – Term Test 1 1

(C) Pavel Sedach Learnfaster.ca

Questions? Suggestions? Email me and I will try to find time to reply. [email protected]

All the best!

Lecture Slides Booklet Solutions Test Solutions Extra notes and advice Advice on which exams and questions to write Corrections

Available October 16th at: http://learnfaster.ca/blog/chem201termtest1/

Day 2

5:00 PM to 6:30Intro, EMR, Electronic

Configurations6:30 to 7:00 Break

7:00 to 8:30 Stoichiometry

8:30 to 8:45 Break8:45 to 10:00 PM Lewis Structures and Bonding

Day 1

11:30 AM to 1:00Intro, EMR, Electronic

Configurations1:00 to 1:30 Break

1:30 to 3:00 Stoichiometry

3:00 to 3:15 Break3:15 to 4:30 PM Lewis Structures and Bonding

What is on the Exam? (Part 1) 2

(C) Pavel Sedach Learnfaster.ca

Atomic Configurations

Exceptions – Columns 6 and 11Cr, Mo, W

Cu, Ag, Au

Configurations up to Row 4

Core Electrons

Valence ElectronsHighest n electrons including

any unfilled d orbitals

Ground vs. Excited State Configurations

Be able to draw s, p and d orbitalsBe able to draw and identify nodes

Paramagnetism ≥1 unpaired electron

Diamagnetism no unpaired electrons

Electromagnetic Radiation E =

hc𝜆= hν

Know that this gives the energy of ONE (1) Photon!

Know how to convert totalJoules to number of photons

Be able to enumerate number of transitions for anatom relaxing to ground state

Understand the difference between Absorption (endothermic) and Emission (exothermic)

Chem 201 is 100 % cumulative, meaning, these topics WILL pop up on the final exam.

Atomic Configurations are especially important because you BUILD on that knowledge for future concepts!

Realistically, when first used, a topic is worth ~20% on Term Test 1, 510% on Term Test 2 and 12 questions on the Final Exam

What is on the Exam? (Part 2) 3

© Pavel Sedach learnfaster.ca

Stoichiometry is a PREREQUISITE,30% of Term Test 1 20% of Term Test 2 Students lose MAJOR marks because Redox Balancing is on TT2 but not taught in class.Why is it tested? Foundational to chemistry AND Part of your Labs and Tutorials.

Lewis Structures

Covalent and Ionic Bonds

Formal Charge

Octet Rule and Exceptions

Best Lewis Structure

Conservation of Mass

Gravimetric Stoichiometry

%w/w

mass to moles

moles to molecules (rare)

molecules to atoms (used in %w/w)

Solutions Stoichiometry

Dilution

%w/v

Solving dilution through pictures

If a stoichiometry concept is NOT used on TT1, it CAN show up on TT2 or the final!

Solution stoichiometry and %w/v and %w/w or density (g/L) (any)

Visual dilution (any, usu.TT1/2) Visual Balancing (any) Redox (any, usu. starts on TT2)Fe2+ + 2 e− ⇌ Fe s

Al s ⇌ Al3+ + 3 e−

3 Fe s + 2 Al s ⇌ 2 Al3+ + 3 Fe s

Breakdown of old exams 4© Pavel Sedach learnfaster.ca

Winter 2016 Fall 2015 Winter 2013 Winter 2012

Multiple ChoiceStoichiometry 18% 18% 25% 12%

EMR 36% 36% 25% 13%

Quantum #s and AOs 27% 27% 31% 44%

Orbitals and Nodes 18% 18% 19% 13%

Periodic Trends 0% 0% 0% 19%Written

Stoichiometry 50% 37% 27% 33%EMR 7% 11% 13%

Quantum #s and AOs 21% 26% 73% 40%

Orbitals and Nodes 21% 26% 0% 13%

The exams ARE 100% cumulative and topics like Periodic Trends and Atomic Orbitals WILL show up again in Organic Chemistry.

Topics like EMR will be a smaller portion of future exams. Right now, they are worth A LOT.

If a stoichiometry format has been tested on TT1, a different type will show up on TT2/the final.

IF you did not get a topic on TT1, you have a month to review before TT2. MAKE SURE you get it! (100% cumulative!)

*Periodic trends weretested on Fall 2016 TT1 AND are part of Chapter 7!

What we offer 5


Booklet Front includes Lecture Slides andOutline Followed by:

Extra Questions and Explanations

Ending in: A guide to studying for exams

Two (2) Copies of the Exam PackageTear out the formula sheet.Write in copy 1 and do select questions during and after class. Use copy 2 toWRITE CLOSED BOOK EXAMS AND GRADE YOURSELF.

The website has full solutions for the rest of the booklet AND the practice exams. The solutions PDF is >30 pages because there are worked solutions in later pages.

Session format: We cover every concept in the session AT LEAST once through the lecture slides.

EVERY QUESTION IN THESE SLIDES IS BASED OFF THE EXAMS.

If we finish a section early, we do several ADDITIONAL exam questions.

The lecture is designed to end early so we can cover questions and run through more exam questions at the end.

x2

How do fireworks work?Lesson 1: Electromagnetic Radiation and Atomic Orbitals

6

(C) Pavel Sedach learnfaster.ca

The Bohr Model of the Atom 7


Electrons are found in distinct energy levels or ‘shells’.What defines the spacing between these shells?

p

n

+

n=1

n=2

n=3

n=4

n=5

n=6

n=1

n=2

n=3

n=4

n=5

n=6

n=7

SHELLS

e

How does Electromagnetic Radiation interact with Matter? 8


p

n

+

n=1

n=2

n=3

1: light from the sun is _______________ energy

So it ________________ the brick wall

2: light from the radio tower is____________ energy

So it _____________________ the brick wall

e

Types of EMR 9

Low High

Low High

high = long low = shortEnergy α Frequency α

𝟏

𝐖𝐚𝐯𝐞𝐥𝐞𝐧𝐠𝐭𝐡

Energy

𝝂, Frequency

λ, Wavelength

Emission and Absorption Spectra 10


In a real atom, as shells are farther out the electron is ______________in Energy.

Shells farther from the nucleus become (farther/closer) in Energy.

When energy is absorbed, it excites an electron to a higher energy level.

p

n

+

e

Emission Spectrum

Absorption Spectrum

EMISSION IS QUANTIZED

ABSORPTION has a minimum thresholdEnergy

Different atoms have different emissions and absorptions because they have a different number of

________________ and ______________ leading to a different orbital/shell spacing

Energy of Light: E = h𝛎 = h𝐜

𝛌therefore 𝝂 = 𝑐

𝜆or c = 𝛎λ 11


E = energy (Joules)h = Planck’s constant (quantization of energy!)𝝂 = f = frequency (1/second or Hz)c = speed of light (2.998 × 108 m/s)𝜆 = wavelength (meters)

E, Energy

𝝂, Frequency

λ, Wavelength

Energy α Frequency α1

𝜆

short wavelength = high frequency = high energylong wavelength = low frequency = low energy

high

high

high = long

low

low

low = short

Review: ABSORPTION (W2016Q4) 12


How many different absorptions are possible and which has the minimum energy? Frequency? Wavelength?

*Technically there are ____________ absorptions as we can go to ANY higher 𝑛/𝑙

Energy

n = 1

n = 2

n = 3

−2.18 × 10−18 J

−5.44 × 10−19 J

−2.42 × 10−19 J

e

Below is the electron shell configuration of hydrogen

p

n

+

n=∞ ∅ Joules

Emission Spectrum

Absorption Spectrum

Review: EMISSION (W2016Q14) 13


If an electron is excited from n=1 to n=4, how many different transitions are possible when it relaxes back to ground level?Which transition produces a photon with the shortest wavelength?

Emission Spectrum

Absorption Spectrum

n = 1

n = 2

n = 3

−2.18 × 10−18 J

−5.44 × 10−19 J

−2.42 × 10−19 J

e

n = 4 −1.36 × 10−19 J

Energy

Below is the electron shell configuration of hydrogen

Review (W2016Q4) 14


As part of your nefarious plan to build a “Moon Base”, you are using a “Laser”to drill a foundation. If you must remove 500 kg of rock and it takes 3.00 kJ of energy to drill away 0.500 kg, how many photons of 50.0 nm wavelength must you fire using the “Laser”?

Bonus: How can you change the light source (sorry, “Laser”) so as less photons are required?

Photoelectric Effect = ‘Ionizing’ or removing an electron from a metal: (F2015, Q10) 15


FREQUENCY of Photon (Hertz)

Energy of e−

(Joules)

threshold frequency of light (𝝂)

ENERGY of Photon (Joules)

Energy of e−

(Joules)

Minimum Energy of light (Joules)

pn+

e

IONIZATION: (Joules or eV) 𝐸𝑝ℎ𝑜𝑡𝑜𝑛 = ℎ𝝂 (Hertz/frequency)

Potassium: 2.0 eV needed to eject electron

3.0 eV1.8 eV 2.3 eV

slow electron

no electron

fastelectron

PHOTOELECTRIC EFFECT: EK = Elight – UEnergy of Electron = Energy of Incident Light –Work Function

*”The photoelectric effect showsexperimental evidence of quantization”

1 photon in = 1 electron out!

ElectronsI’m in a place that's neither here nor there...

Lesson 2: Quantum Numbers

16


The De Broglie Hypothesis 17

ℎ = Planck’s constant𝑚 =mass (kilograms)𝑣 = velocity (meters/second)p =mass × velocity = momentum

Matter has wavelike properties

𝜆 =ℎ𝑝=

ℎ𝑚𝑣

Heisenberg Uncertainty Principle Δ𝑥Δ𝑝 ≥ തℎwhere x is position and p is momentum

+

constructive(Allowed)

e+

The Quantum Mechanical Model

destructive(Not Allowed)

constructive destructive

(C) Pavel Sedachlearnfaster.ca

e

Electron Configurations and Orbitals 18


An atomic orbital is the probable area of finding an electron.

Boron

Nitrogen

Potassium

s orbitals

p orbitals

d orbitals

𝑠

𝑥

𝑦 𝑧

𝑝𝑥 𝑝𝑦 𝑝𝑧

𝑥

𝑦 𝑧

𝑥

𝑦 𝑧

𝑥

𝑦 𝑧

𝑑𝑥𝑦 𝑑𝑥𝑧 𝑑𝑦𝑧

𝑥

𝑧 𝑦 𝑦 𝑥

𝑑𝑥2−𝑦2 𝑑𝑧2

𝑥

𝑦 𝑧

𝑥

𝑦 𝑧

𝑥

𝑦 𝑧

𝑧

Atomic Orbital Boundary Diagrams

Bohr vs. Quantum Electronic Configurations

Energy

n = 1

n = 2

n = 3

n = 4

n = 5

NitrogenHydrogen

1s

2s

3s

4s

5s

2p

3d

3p

1s

2s

3s

4s

5s

2p

3d3p

Energy


19

Configuration: Configuration:

4p

Bohr vs. Quantum Electronic ConfigurationsEnergy

n = 1

n = 2

n = 3

n = 4

n = 5

Si (Silicon) Si13+ (Silicon Ion)

1s

2s

3s

4s

5s

2p

3d

3p

1s

2s

3s

4s

5s

2p

3d3p

Energy


20

Configuration: Configuration:

Which element is depicted in the diagram below? 21


Aufbau Principle (Low to High Energy)Hund’s Rule (Single before Pairing)Pauli Exclusion Principle

Diamagnetic? Paramagnetic?

Consequence of Paramagnetism? Atom/molecule is affected by magnetic fields!

n = 1

n = 2

n = 3

n = 4

n = 5

1s

2s

3s

4s

5s

2p

3d

3p

n = ∞

Energy

↿⇂ ↿⇂ ↿⇂

↿⇂

↿⇂

↿⇂

↿⇂↿⇂ ↿⇂ ↿⇂

↿⇂ ↿ ↿ ↿ ↿

Most Chem 201 instructors want single headed arrows.You have to be critical of your work but you SHOULDN'T BE critical of yourself!

Exceptions to Electron Filling

(C) Pavel Sedach

learnfaster.ca

22

Electronic filling for exceptions

(C) Pavel Sedach

learnfaster.ca

Cr (chromium)

n = 1

n = 2

n = 3

n = 4

n = 5

1s

2s

3s

4s

5s

2p

3d

3p

Configuration:

23

Energy

Valence and Core Electrons 24


The Valence Electrons are the highest nvalue and highest energy orbitals, including any UNFILLED dorbitals:

Vanadium (V): 1s22s22p63s23p64s23d3

P:

Cu:

Identify the valence electron in EVERY previous diagram.

Draw an electron box diagram of Neon, circle the valence and draw a square around the core electrons.

Ion Configurations CATIONS (+ve charge) ANIONS (ve charge) (C) Pavel Sedach learnfaster.ca

Titanium

Ti s

Ti+

Ti2+

Ti3+

Ti4+

Ti5+

25

Losing electrons1. The highest n (shell, e.g. 4)

electrons are lost first 2. WITHIN the highest n, the

highest subshell (e.g. p) electrons are lost first

Gaining electrons1. IF electrons are added, they

follow the Aufbau rule (everything is as normal!)

Arsenic

As s

As+

As2+

As3+

As4+

As5+

Chlorine

Cl g

Cl−

Cl2−

Cl3−

Ions, Excited States and Neutral Atoms (C) Pavel Sedachlearnfaster.ca

Chlorine

# of e−:

Condensed:

26

Chloride Ion Excited ChlorineEnergy

n = 1

n = 2

n = 3

1s

2s

3s

2p

3p

n = 1

n = 2

n = 3

n = 4

1s

2s

3s

4s

2p

3d

3p

n = 5 5s

n = 1

n = 2

n = 3

1s

2s

3s

2p

3p

# of e−:

Condensed:

# of e−:

Condensed:

Cl Cl Cl

ions always have a __________number of electrons

excited states have the __________ number of electrons as the neutral atom

Review


Which one of the following transitions for the hydrogen atom would emit a photon of the shortest wavelength?

a) n = 2 to n = 1

b) n = 3 to n = 2

c) n = 5 to n = 6

d) n = 6 to n = 5

27

Like the session so far?

Share it with your friends!

https://www.facebook.com/prep101uofc/

Let them know.

Don’t have any friends? Me neither. Lol, just joking. Butseriously.

28


Periodic Properties 29

© Pavel SedachLearnfaster.ca

Electronegativity – ‘a measure of how much atoms like electrons within a bond’

Zeff increases left to right so electronegativity should too

*arrows show direction in which magnitude of the trends increases

Other trends include:

Atomic Radius – the size of the neutral atom

Ionization energy – the energy needed to remove an e from a gaseous atom

Electron affinity – the negative ofthe energy released when an e is added to a gaseous atom

Effective Nuclear Charge Zeff = Z − S 30


Effective nuclear charge = # protons # core electrons.

Zeff essentially an estimate of the number of protons pulling that electron in towards the atom.

Higher Zeff = electron is HARDER to remove.

Zeff Increases left to right across the periodic table. Due to the way Zeff is calculated in Chem 201, we don’t see a decrease goingdown a Group but we should. Zeff for the dblock is generally not discussed but even unfilled d acts as core e−.

Al Si P S

Protons 13 14 15 16

Core Electrons 10 10 10 10

Zeff 3 4 5 6

Zeff

Large Radii

Ionic Radius 31


Cations are ALWAYS smaller than their neutral atomsAnions are ALWAYS larger than their neutral atoms

Arrange the following atoms in order of size (big to small): Ge, F, Y, Br, C

Arrange the following ions and atoms in order of size: S2−, O2−, Ne, Cl−, K+, N3−

Increasin

g Size

Increasing Size

SmallRadii

LosesElectron

GainsElectron

Anion

XX+X−

Cation Neutral

Ionization Energy is the energy needed to remove an e from an atom (endothermic) 32


Explain why the ionization energy of Be is greater than B?

N is greater than O?

Ne is greater than F?

Why does period 2 have a greater ionization energy than period 3?

+475

+675

+875

+1075

+1275

+1475

+1675

+1875

+2075

1 2 3 4 5 6 7 8

1st Ionization Energy (kJ/mol)

Column/Group (not including the dblock)

Period 2

Period 3

Ionization energy (kJ/mol) is ALWAYS endothermic(it always takes energy to remove electrons from an atom!)

Equation for Ionization: X → X+ + e−

Successive Ionization Energies of Aluminum 33


The second ionization energy for an atom is always greater than the first. Why?

Where is there an enormous jump in ionization energy and why?

What is the enthalpy for Al → Al3+ + 3e−?

Ionization energy Enthalpy kJ

molBeginning Shorthand

ConfigurationEquation Final Shorthand

Configuration

1st 578[Ne]

Al → Al+ + e−[Ne]

2nd 1817[Ne]

Al+ → Al2+ + e−[Ne]

3rd 2745[Ne]

Al2+ → Al3+ + e−[Ne]

4th 11577 Al3+ → Al4+ + e−

5th 14842 Al4+ → Al5+ + e−

Electron Affinity Magnitude of how exothermic the absorption of an electron is. 34


Why does Phosphorus have a lower electron affinity than Sulphur?

What process is described by the enthalpy of attachment of the second electron of Aluminum?

Electron Affinity (kJ/mol)

Review 35


1. What are the four periodic trends and how do they vary on the periodic table?

2. What are the exceptions to some trends and why do they occur?

3. Rank the following in order of ionization energy, electronegativity, electron affinity and atomic radius:

N, O, F, Ne

Stoichiometryand Solutions

36


Significant Figures (F2015 Q2) 37

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Leading zeroes don’t count (zeroes on the left don’t add information)

0.000011500 = 1.1500 × 10−5

Zeroes on the right tell us precision. Ex. 50 means 50 ± 0.5 whereas 50.0 means 50.0 ± 0.05

Addition and Subtraction Least number of decimals:100 − 0.1547869 = 99.8452131 = 100

If two numbers use different scientific notation, convert to same notation:17.2 × 103 − 5.5 × 102 =

172 × 102 − 5.5 × 102 = 166.5 = 167

Multiplication Least number of sig. figs.1230 × 16 = 19680 = 2.0 × 104

Significant figures SHOULD be evaluated at every step.IF THERE IS A CALCULATION WITH BOTH ADDITION AND SUBTRACTION AND MULTIPLICATION, BE CAREFUL!!!!

Practice: 24.71 − 24.0 = 24.71 × 24.0 =

Basic Stoichiometry 38


I have 6 wheels and 4 frames, given the following equation:

2 wheels + 1 frame 1 bicycle

How many bicycles can I make?

Given that 1 bicycle was broken during assembly, what was my percent yield?

Stoichiometry is a four step process: 39(C) Pavel Sedach learnfaster.ca

1. Balance, 2. Convert to moles, 3. Use a molar ratio, 4. Convert moles to unit required

If I react 10.0 g of sucrose (C12H22O11) with 40.0 g of O2, what will my yield of CO2 be?

C12H22O11 + O2 → CO2 + H2O

H2N2 O2 F2

Cl2Br2I2

Review 40(C) Pavel Sedach learnfaster.ca

If my actual yield of CO2 g was 10.0 g, what was my percent yield?

How much of my excess reagent (in grams) was left?

Balancing Stoichiometry with Pictures 41


1. Balance visually.2. Convert grams to moles and use stoichiometric coefficients as normal3. Convert moles of the limiting reagent to the compound you want

Dilution 42


moles = molesmol

L× L =

mol

L× L C1V1 = C2V2

How much 1.00 M H2SO4(aq) do I need in order to make 5.00 L of a 0.15 mol/L sulfuric acid solution?

What was the dilution factor of the solution?

How much water was added to the solution?

%w/w and %w/v 43


% w/w is literally the fraction of your compound for every gram of total solution. For example:How many grams of iron are in a 2.00 %w/w FeO salt crystal of 550 grams?

How many grams of iodine are in a 200 mL of a 15 %w/v solution of iodine?

How many atoms of iodine is this?

Review 44


What would be the most stable cation (s) of Germanium? Why?

In order for an oxygen atom to become O+, what must happen? Draw the orbital diagrams

Lewis Diagrams

45


Carbon has 4 valence e−, all of them can be bonded

Carbon typically forms 4 bonds

Nitrogen has 5 valence e−, 2 arepaired, 3 are left to bond

Nitrogen forms 3 bonds

Oxygen has 6 valence e−, 4 arepaired, 2 are left to bond

Oxygen forms 2 bonds

Covalent Compounds 46


Simplified Lewis Structures and Dipoles 47


SiF4CO2 H2S

CH2Cl2

Systematic Lewis Structures 48


Step 1 – Count the total number of valence electrons in the structureStep 2 – Arrange the peripheral atoms around the central atom/structure and single bond themStep 3 – Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom.Step 4 – Calculate the formal charges and minimize it by preparing resonance structures

Formal Charge = Valence electrons – lone pair electrons – bonds

Incomplete Valence: BF3 Expanded Valence: SO3

Systematic Lewis Structures 49


Step 1 – Count the total number of valence electrons in the structureStep 2 – Arrange the peripheral atoms around the central atom/structure and single bond themStep 3 – Place remaining electrons around peripheral atoms. Place any extra electrons around the central atom.Step 4 – Calculate the formal charges and minimize it by preparing resonance structures

Formal Charge = Valence electrons – lone pair electrons – bonds

Odd Electron Species: NO2

Resonance, Bond Order and Average Charge 50


Identify the major, minor and intermediate resonance contributors:

OCN−

Does the above compound have an effective resonance hybrid?



Identify the major, minor and intermediate resonance contributors:

NO2

Does the above compound have an effective resonance hybrid?



HSO4−

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