Search found 65 matches

by Zubair Ahmed 1L
Thu Feb 14, 2019 8:39 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 3/2R vs 5/2R
Replies: 8
Views: 40

Re: 3/2R vs 5/2R

It is very important to know the difference between. 5/2R is used for constant pressure and 3/2R is used for constant volume. You will have to use either one depending on the context of the question.
by Zubair Ahmed 1L
Thu Feb 14, 2019 8:37 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ΔU= 3/2nRT
Replies: 5
Views: 32

Re: ΔU= 3/2nRT

I have never really come across any question where I had to use this equation. It is basically another way to state the fact that delta U=0 for an isothermal, reversible expansion. You might want to learn it just in case.
by Zubair Ahmed 1L
Thu Feb 14, 2019 8:34 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: adding entropy
Replies: 5
Views: 31

Re: adding entropy

Since entropy is a state function, you can simply add the entropy of the change in volume and temperature to find the total change in entropy of the system.
by Zubair Ahmed 1L
Thu Feb 14, 2019 8:32 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Temperature and Equilibrium
Replies: 2
Views: 12

Re: Temperature and Equilibrium

If the reaction is endothermic, increasing the temperature will lead to an increase in product formation. If the reaction is exothermic, an increase in temperature will lead to an increase in of reaction formation.
by Zubair Ahmed 1L
Thu Feb 07, 2019 1:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Irreversible vs. Reversible Expansion
Replies: 4
Views: 34

Re: Irreversible vs. Reversible Expansion

A key difference between reversible and irreversible expansion is that a reversible reaction does more work than an irreversible reaction. Also, in the real world, irreversible reactions are much more realistic.
by Zubair Ahmed 1L
Thu Feb 07, 2019 1:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs. Specific Heat
Replies: 2
Views: 39

Re: Heat Capacity vs. Specific Heat

The equation "q = nC∆T" refers to the molar heat capacity because it measures the heat required to raise 1 mol of a substance by 1 degree celsius. We can ignore the "n" in the equation for the calorimeter because we are looking for the heat capacity instead.
by Zubair Ahmed 1L
Thu Feb 07, 2019 12:54 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quiz 1 Number 3c
Replies: 6
Views: 43

Re: Quiz 1 Number 3c

Since the question is asking for concentration values, the units for your answer should be molarity, mol/L.
by Zubair Ahmed 1L
Thu Feb 07, 2019 12:48 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm
Replies: 8
Views: 78

Re: Midterm

Dr. Lavelle mentioned on his website that the midterm covers everything we learned so far till the end of entropy.
by Zubair Ahmed 1L
Wed Jan 30, 2019 7:03 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 11
Views: 83

Re: Test #1

Yea we get them back in discussion this week!
by Zubair Ahmed 1L
Wed Jan 30, 2019 7:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Isolated systems
Replies: 10
Views: 48

Re: Isolated systems

An isolated system juts implies that that there is no exchange of energy or matter with the surroundings. An isolated system could have a constant volume but it is not necessary.
by Zubair Ahmed 1L
Wed Jan 30, 2019 6:53 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKa vs. pH
Replies: 11
Views: 63

Re: pKa vs. pH

The pKa and the pH represent two different things. The pKa is the -log(Ka) and can be used to determine the strength of an acid. On the other hand, the pH is the -log(H+) concentration.
by Zubair Ahmed 1L
Wed Jan 30, 2019 6:50 pm
Forum: Ideal Gases
Topic: kc vs kp
Replies: 15
Views: 74

Re: kc vs kp

Kc and Kp do not represent the same thing. Kp refers to the equilibrium constant using partial pressures while Kc refers to the equilibrium constant using concentration values.
by Zubair Ahmed 1L
Thu Jan 24, 2019 1:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: When to ignore change in Acid
Replies: 5
Views: 36

Re: When to ignore change in Acid

Yes, you would ignore the change in acid when the Ka value is less than 10^-3 because it is considered a weak acid and the change in concentration is so small that it can be ignored.
by Zubair Ahmed 1L
Thu Jan 24, 2019 1:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Test 1
Replies: 8
Views: 81

Re: Test 1

It is a great to know a common list of strong acids and bases for the test but it is not required. It is important to know that if the Ka/Kb value is less than 10^-3 it is a weak acid/base.
by Zubair Ahmed 1L
Thu Jan 24, 2019 1:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: endothermic vs exothermic
Replies: 6
Views: 41

Re: endothermic vs exothermic

Le Chatelier's Principle refers to the process of chemical reactions adjusting to minimize the affect of certain changes. Moreover, exothermic means that heat is released as a part of the reaction and endothermic means that heat is required for the reaction to proceed.
by Zubair Ahmed 1L
Thu Jan 24, 2019 1:26 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Calculating Q
Replies: 11
Views: 60

Re: Calculating Q

Both Q and K use the same equation during calculation. However, K is used at equilibrium while Q can be used at any point during a reaction. It is important understand the fact that Q can be changed due to changes in pressure and concentration but K does not. K shifts only when there is a change in ...
by Zubair Ahmed 1L
Thu Jan 17, 2019 11:41 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Changes to K value
Replies: 9
Views: 41

Re: Changes to K value

Only temperature can affect the K value
by Zubair Ahmed 1L
Thu Jan 17, 2019 11:40 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc of the Forward/Reverse Reaction
Replies: 6
Views: 37

Re: Kc of the Forward/Reverse Reaction

The Kc of the reverse reaction is the reciprocal of the forward reaction. For example, if the Kc of the forward reaction is 5, the Kc of the reverse reaction is 1/5.
by Zubair Ahmed 1L
Thu Jan 17, 2019 11:37 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Acid and Base Equilibria
Replies: 7
Views: 39

Re: Acid and Base Equilibria

megangeorge-1K wrote:For this week should we be submitting homework from chapter 12?

We can choose Hw questions from either Chemical Equilibria or Acids and Bases outlines.
by Zubair Ahmed 1L
Thu Jan 17, 2019 11:34 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables [ENDORSED]
Replies: 11
Views: 55

Re: ICE Tables [ENDORSED]

ICE Tables are specifically used to find the equilibrium concentration of products and reactants when given the initial concentration. The value of the products will not always be zero. It will be values given from the question.
by Zubair Ahmed 1L
Fri Jan 11, 2019 10:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Liquids and Solids in Equilibrium Constants
Replies: 5
Views: 35

Re: Liquids and Solids in Equilibrium Constants

The values of the change in concentration of solids and liquids are so small that they can be ignored when solving for the equilibrium constant.
by Zubair Ahmed 1L
Fri Jan 11, 2019 9:59 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kc of the Forward/Reverse Reaction
Replies: 6
Views: 37

Re: Kc of the Forward/Reverse Reaction

The Kc is representative of both the forward and reverse reactions because they reaction rates are reciprocals of one another.One way to visually see this is by solving for the K value of both reactions and you will see that the two rates are the inverse of one another.
by Zubair Ahmed 1L
Fri Jan 11, 2019 9:54 am
Forum: Ideal Gases
Topic: What does K represent?
Replies: 9
Views: 41

Re: What does K represent?

K represents the equilibrium constant which is denoted by the concentration of products over the concentration of the reactant. If both of the concentrations are the same, the K value would be one.
by Zubair Ahmed 1L
Fri Jan 11, 2019 9:52 am
Forum: Ideal Gases
Topic: Q and K [ENDORSED]
Replies: 35
Views: 783

Re: Q and K [ENDORSED]

Both have the same formula, but they calculate different things.
by Zubair Ahmed 1L
Wed Dec 05, 2018 8:44 pm
Forum: Naming
Topic: Common Ligand names Table
Replies: 1
Views: 28

Re: Common Ligand names Table

I believe you are. However, you do not need to memorize ligand notations such as edta, ox, en, etc.
by Zubair Ahmed 1L
Wed Dec 05, 2018 8:39 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Versus Lewis
Replies: 3
Views: 29

Re: Bronsted Versus Lewis

I believe it is that all Bronsted acids and bases are Lewis acids and bases, but not all Lewis acids and bases are Bronsted acids and bases.
by Zubair Ahmed 1L
Wed Dec 05, 2018 8:35 pm
Forum: Properties & Structures of Inorganic & Organic Bases
Topic: HF ion
Replies: 3
Views: 24

Re: HF ion

HF is considered a weak acid due to fluorine's high electronegativity. Acids are considered strong when they completely dissociate in water and have longer, weaker bonds.
by Zubair Ahmed 1L
Wed Dec 05, 2018 6:27 pm
Forum: Naming
Topic: Naming Coordination Compounds
Replies: 4
Views: 35

Re: Naming Coordination Compounds

Yea we have to memorize them. However, he said that we do not need to memorize notations such as edta, en, ox, etc.
by Zubair Ahmed 1L
Sat Dec 01, 2018 5:15 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar Molecules
Replies: 12
Views: 40

Re: Polar Molecules

In order to determine if a molecule is polar or non-polar, you can draw out the lewis structure and identify the dipole moments of the given molecule. If the dipole moments cancel, the molecule is non-polar. If the dipole moments do not cancel, the molecule is polar.
by Zubair Ahmed 1L
Sat Dec 01, 2018 5:00 pm
Forum: Hybridization
Topic: Pi bonds in triple bond
Replies: 17
Views: 256

Re: Pi bonds in triple bond

There are 2 pi bonds and one sigma bond in a triple bond.
by Zubair Ahmed 1L
Sat Dec 01, 2018 4:56 pm
Forum: Naming
Topic: CN naming?
Replies: 3
Views: 26

Re: CN naming?

The book uses the "-ido" suffix when naming coordination compounds, but Dr. Lavelle use the suffix "-o". They are both technically correct but I would use the notation Dr. Lavelle uses.
by Zubair Ahmed 1L
Sat Dec 01, 2018 4:54 pm
Forum: Hybridization
Topic: Hybridization Notation
Replies: 10
Views: 80

Re: Hybridization Notation

Either notation is acceptable but Dr. Lavelle mentioned that he prefers the d orbital to placed at the end.
by Zubair Ahmed 1L
Sat Nov 24, 2018 12:59 pm
Forum: Hybridization
Topic: Writing out Hybridization
Replies: 8
Views: 38

Re: Writing out Hybridization

Dr. Lavelle mentioned that it does not matter which notation you use when writing out the d-block in hybridization, but he did say that he will be writing it as sp^3d in lecture.
by Zubair Ahmed 1L
Sat Nov 24, 2018 12:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 41

Re: Polarity

We typically indicate dipole moments by drawing an arrow towards the partial negative end of a molecule. If arrows cancel out, we know hat the molecule in non-polar.
by Zubair Ahmed 1L
Sat Nov 24, 2018 12:46 pm
Forum: Hybridization
Topic: double bonds
Replies: 14
Views: 106

Re: double bonds

In a double bond there is one pi bond and one sigma bond. In a triple bond, there is one sigma bond and two pi bonds now due an additional side-to-side overlap.
by Zubair Ahmed 1L
Sat Nov 24, 2018 12:39 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 10
Views: 114

Re: Test 3

I would study both outline 3 and 4 just to be safe.
by Zubair Ahmed 1L
Wed Nov 14, 2018 10:51 pm
Forum: Lewis Structures
Topic: Expanded Octets
Replies: 9
Views: 111

Re: Expanded Octets

Elements that contain a d-orbital can have expanded octets.
by Zubair Ahmed 1L
Wed Nov 14, 2018 10:45 pm
Forum: Dipole Moments
Topic: How do you draw dipole moments
Replies: 6
Views: 61

Re: How do you draw dipole moments

To indicate a dipole moment, you need to draw an arrow pointing towards the most electronegative element.
by Zubair Ahmed 1L
Wed Nov 14, 2018 10:38 pm
Forum: Lewis Structures
Topic: Boron Trifluoride
Replies: 8
Views: 76

Re: Boron Trifluoride

Boron is an exception to the octet rule, just like any other element in group 13 such as Aluminum.
by Zubair Ahmed 1L
Wed Nov 14, 2018 10:35 pm
Forum: Lewis Structures
Topic: Formal Charge
Replies: 14
Views: 154

Re: Formal Charge

When drawing Lewis structures for ions, it is best of the central atom to have a formal charge of 0 and to place any negative charge on the outer elements because that is when it is most stable.
by Zubair Ahmed 1L
Thu Nov 08, 2018 5:14 pm
Forum: Bond Lengths & Energies
Topic: Tests
Replies: 5
Views: 75

Re: Tests

Yup, just one more test and then the final.
by Zubair Ahmed 1L
Thu Nov 08, 2018 5:12 pm
Forum: Lewis Structures
Topic: Mystery Element
Replies: 4
Views: 60

Re: Mystery Element

Just to reiterate, the central element is typically the least electronegative atom and a good way to check that is to calculate the formal charges of all the elements in the molecule.
by Zubair Ahmed 1L
Thu Nov 08, 2018 5:09 pm
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 68
Views: 20125

Re: formula units [ENDORSED]

Arlene Linares 3A wrote:For the midterm, does anyone knows how much the units are worth when graded?

I believe both units and sig figs are each worth one point.
by Zubair Ahmed 1L
Thu Nov 08, 2018 5:07 pm
Forum: Lewis Structures
Topic: Double Bonds
Replies: 7
Views: 83

Re: Double Bonds

I typically include double bonds to lower the formal charge of the an element. It is important to remember to not exceed 4 bonds per element unless the element can have an expanded octet such as sulfur and phosphorous.
by Zubair Ahmed 1L
Thu Nov 08, 2018 5:03 pm
Forum: Lewis Structures
Topic: Formal charge question
Replies: 9
Views: 101

Re: Formal charge question

When I draw out Lewis structures, I count all the numbers of valence electrons in the given molecule and follow the octet guidelines given to us by Dr. Lavelle. I calculate formal charge when I need to draw out the lowest energy Lewis structure.
by Zubair Ahmed 1L
Wed Oct 31, 2018 10:24 am
Forum: Resonance Structures
Topic: How does a resonance structure work?
Replies: 10
Views: 175

Re: How does a resonance structure work?

Just to reiterate, resonance structures are basically lewis structures that can be written in multiple forms, the difference being the arrangement of the bonds between each resonance structure. The chemical properties are all the same.
by Zubair Ahmed 1L
Wed Oct 31, 2018 10:17 am
Forum: Lewis Structures
Topic: Valence Electrons
Replies: 7
Views: 66

Re: Valence Electrons

Phosphorous can have 5 bonds since it is in Period 3 and the d-block is included within it. As a result, it has 10 valence electrons and can create 5 bonds.
by Zubair Ahmed 1L
Wed Oct 31, 2018 10:13 am
Forum: Lewis Structures
Topic: Central Atom
Replies: 13
Views: 153

Re: Central Atom

When dealing with Lewis structures, the atom with the lowest ionization energy would be used as the central atom. Hydrogen is never the central atom so it would be Carbon in this case.
by Zubair Ahmed 1L
Wed Oct 31, 2018 10:10 am
Forum: Ionic & Covalent Bonds
Topic: Covalent Bonds
Replies: 16
Views: 164

Re: Covalent Bonds

Just to reiterate, nonmetals(anions) cannot become cations due to their high electronegativity and lack of electrons in their valence shell. Nonmetals such as chlorine with 7 valence electrons only needs one more electron to complete their octet so they would attract other elements in giving up an e...
by Zubair Ahmed 1L
Wed Oct 24, 2018 2:08 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Test 2 outline
Replies: 4
Views: 63

Re: Test 2 outline

Yes. Basically, know what all the quantum numbers are and what they mean and know how to use them to label a given orbital.
by Zubair Ahmed 1L
Wed Oct 24, 2018 10:25 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: exceptions: chromium & copper
Replies: 2
Views: 27

Re: exceptions: chromium & copper

No, the 3d orbital would still be considered to be at a a lower energy level than the 4s orbital regardless whether or not the 4s orbital is completely filled.
by Zubair Ahmed 1L
Wed Oct 24, 2018 10:18 am
Forum: DeBroglie Equation
Topic: equation definition
Replies: 5
Views: 119

Re: equation definition

The De Broglie equations includes the mass and velocity of a given particle while the normal wavelength equation can also be associated with light. You can tell which equation to use in a given situation based upon the parameters listed in the question.
by Zubair Ahmed 1L
Wed Oct 24, 2018 10:11 am
Forum: Properties of Light
Topic: kg or g [ENDORSED]
Replies: 11
Views: 182

Re: kg or g [ENDORSED]

mostly all the equations we were taught in the quantum world chapter use kilograms as the unit for mass since kg is the SI unit.
by Zubair Ahmed 1L
Tue Oct 16, 2018 11:15 am
Forum: Properties of Light
Topic: E=hv
Replies: 13
Views: 136

Re: E=hv

yes, E represents the amount of energy per photon. The units for E is Joules.
by Zubair Ahmed 1L
Tue Oct 16, 2018 11:12 am
Forum: *Particle in a Box
Topic: Hw assignment?
Replies: 7
Views: 170

Re: Hw assignment?

Yea make sure to only do questions from the Quantum World chapter. I asked my TA the same question and he made it very clear to not do problems from the Fundamentals section nor from the Chemical Bonds section because we have not covered it yet.
by Zubair Ahmed 1L
Tue Oct 16, 2018 11:09 am
Forum: Properties of Light
Topic: Mass
Replies: 4
Views: 47

Re: Mass

Light cannot gain mass when it is stagnant because the particles are always in constant motion.
by Zubair Ahmed 1L
Tue Oct 16, 2018 11:06 am
Forum: Properties of Light
Topic: Vocab
Replies: 5
Views: 59

Re: Vocab

In our case, the thing being quantized is energy. When energy is quantized, energy is packaged into small discrete packets of energy called quanta.
by Zubair Ahmed 1L
Tue Oct 09, 2018 5:44 pm
Forum: Empirical & Molecular Formulas
Topic: Going from empirical to Molecular formula
Replies: 14
Views: 265

Re: Going from empirical to Molecular formula

Yea, it should be a whole number. The questions are usually phrased in a way in which the multiple of of the molecular to empirical formula is easy to work with. However, there may be examples where the multiple is "3.99" or "4.02". In this case, you would round to the nearest wh...
by Zubair Ahmed 1L
Tue Oct 09, 2018 5:40 pm
Forum: Administrative Questions and Class Announcements
Topic: Periodic Table
Replies: 6
Views: 78

Re: Periodic Table

Yes, periodic tables will be provided during the exam.
by Zubair Ahmed 1L
Tue Oct 09, 2018 5:39 pm
Forum: SI Units, Unit Conversions
Topic: Quiz 1- Addition to what we should know?
Replies: 5
Views: 163

Re: Quiz 1- Addition to what we should know?

I asked him this same question as well! For this quiz specifically, we do not need to know the names of specific cations and anions. He said that the way we will eventually memorize them is over time by practicing questions and solving problems. It will become second nature to us.
by Zubair Ahmed 1L
Tue Oct 09, 2018 5:35 pm
Forum: Properties of Light
Topic: C=Delta x V
Replies: 6
Views: 46

Re: C=Delta x V

From the equation, c(speed of light, 3*10^8 m/s)=lambda(wavelength, nm)*v(frequency, Hz), you are able to figure out many different variables and understand conceptual topics. For example, the speed of light, "c", is always a constant. This tells us that if that if the wavelength increases...
by Zubair Ahmed 1L
Sun Sep 30, 2018 8:49 pm
Forum: SI Units, Unit Conversions
Topic: How does grading for discussion posts work?
Replies: 73
Views: 1309

Re: How does grading for discussion posts work?

As long as you participate in any of the the given discussion topics or ask your own question a minimum of 3 times a week, you will receive a maximum of 3 points for the entire week for 10 weeks. Chemistry Community counts for 30 points of your entire grade for the quarter. The syllabus for this cla...
by Zubair Ahmed 1L
Sun Sep 30, 2018 8:30 pm
Forum: Administrative Questions and Class Announcements
Topic: Solutions Manual
Replies: 9
Views: 325

Re: Solutions Manual

I have the solutions manual for the 6th edition textbook and it is very helpful for me. It gives me the ability to check my answers and shows me the steps for certain questions I have trouble figuring out. It is a great way to understand new material as well if you want to get ahead and try new sets...
by Zubair Ahmed 1L
Sun Sep 30, 2018 8:14 pm
Forum: Balancing Chemical Reactions
Topic: Short cuts/methods for balancing equations
Replies: 15
Views: 151

Re: Short cuts/methods for balancing equations

For me personally, I start by balancing the gases and then make my way to the solids. It generally works and makes things easier for me.
by Zubair Ahmed 1L
Sun Sep 30, 2018 5:03 pm
Forum: Student Social/Study Group
Topic: 7 sets of problems?
Replies: 5
Views: 240

Re: 7 sets of problems?

Hello,

Towards the end of the syllabus, Dr. Lavelle has a list of problems that need to be completed for homework every week. You can choose any of those seven to complete.

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