Search found 65 matches

by Emma Popescu 1L
Fri Jan 17, 2020 12:19 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pressure change
Replies: 4
Views: 12

Re: pressure change

If the volume decreases and more moles of gas are on the left, the reaction shifts to the right. If the volume decreases and there are more moles of gas on the right, then the reaction shifts to the left. The reaction responds to minimize the effect of increasing pressure (by decreasing volume).
by Emma Popescu 1L
Fri Jan 17, 2020 12:16 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 5
Views: 38

Re: Le Chatelier's Principle

Le Chatelier's principle states that chemical reactions adjust so as to minimize the effect of changes, which applies to temperature, pressure and concentration.
by Emma Popescu 1L
Fri Jan 17, 2020 12:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Endo/Exothermic Reactions
Replies: 6
Views: 23

Re: Endo/Exothermic Reactions

The bond of X2 is broken which requires energy so it is endothermic.
by Emma Popescu 1L
Fri Jan 17, 2020 12:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: inert gas added
Replies: 4
Views: 12

Re: inert gas added

Adding an inert gas at constant volume will change the total pressure but not the partial pressures of the other gases in the container. The number of moles per unit volume remains the same so the equilibrium does not change
by Emma Popescu 1L
Fri Jan 17, 2020 12:04 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas does not change pressure?
Replies: 7
Views: 28

Re: Inert Gas does not change pressure?

Increasing the pressure by adding an inert gas at constant volume has no effect because only the partial pressures of the reactants and products are important. Adding an inert gas at constant volume will change the total pressure but not the partial pressures of the other gases in the container. The...
by Emma Popescu 1L
Wed Jan 08, 2020 3:11 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reverse reaction
Replies: 6
Views: 32

Re: Reverse reaction

Based on le Châtelier’s Principle, when we make changes to a reaction at equilibrium, the equilibrium will respond by trying to undo the change. For example, if the concentration of products increases, then the reaction forming reactants is favored (reverse reaction). Additionally, if the forward re...
by Emma Popescu 1L
Wed Jan 08, 2020 2:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Solvents
Replies: 5
Views: 27

Re: Solvents

The change in solvent concentration is insignificant because it is in excess.
by Emma Popescu 1L
Wed Jan 08, 2020 2:56 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: solids and liquids
Replies: 2
Views: 20

Re: solids and liquids

The molar concentration of a pure substance does not change in a reaction so solids and liquids are not included in K expression.
by Emma Popescu 1L
Wed Jan 08, 2020 2:54 pm
Forum: Ideal Gases
Topic: Q and K
Replies: 7
Views: 38

Re: Q and K

Q is the reaction quotient while K is the equilibrium constant. Q is used to determine which direction a reaction will shift to reach equilibrium. If K > Q, the reaction will proceed forward but if K < Q, the reaction will proceed in the reverse direction.
by Emma Popescu 1L
Wed Jan 08, 2020 2:47 pm
Forum: Ideal Gases
Topic: K and Q
Replies: 13
Views: 48

Re: K and Q

Q is the reaction quotient. It can be used to determine which direction a reaction will shift to reach equilibrium based on the value of K, the equilibrium constant. If Q = K then the system is already at equilibrium.
by Emma Popescu 1L
Sun Dec 08, 2019 10:52 pm
Forum: Administrative Questions and Class Announcements
Topic: 14A FInal
Replies: 6
Views: 82

Re: 14A FInal

We will get it back the second week of winter quarter
by Emma Popescu 1L
Sun Dec 08, 2019 10:50 pm
Forum: Bond Lengths & Energies
Topic: Dissociation Bond Length
Replies: 3
Views: 52

Re: Dissociation Bond Length

I don't think so. However, we should know how to compare which molecule would have a higher dissociation energy.
by Emma Popescu 1L
Sun Dec 08, 2019 10:47 pm
Forum: Air Pollution & Acid Rain
Topic: Final Exam
Replies: 4
Views: 72

Re: Final Exam

He also said we should do acid rain problems from the textbook
by Emma Popescu 1L
Fri Dec 06, 2019 3:17 pm
Forum: Calculating the pH of Salt Solutions
Topic: Question 6D.11
Replies: 2
Views: 40

Re: Question 6D.11

I was also really confused by this problem. However, this link helped: https://chemed.chem.purdue.edu/genchem/ ... metals.php
by Emma Popescu 1L
Fri Dec 06, 2019 3:13 pm
Forum: Air Pollution & Acid Rain
Topic: Acid Rain textbook
Replies: 1
Views: 62

Acid Rain textbook

Dr. Lavelle said in lecture that we should work on acid rain problems from the textbook. However, none of the homework problems refer to acid rain. I was wondering what pages in the textbook refer to acid rain and what problems is he referring to?
by Emma Popescu 1L
Fri Nov 29, 2019 9:44 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Inorganic vs Organic Acids
Replies: 3
Views: 47

Re: Inorganic vs Organic Acids

What pages can I find information about organic vs. inorganic acids in the textbook?
by Emma Popescu 1L
Fri Nov 29, 2019 9:37 pm
Forum: Identifying Acidic & Basic Salts
Topic: identifying acids and bases
Replies: 4
Views: 38

Re: identifying acids and bases

By drawing out the lewis structures, you can see the electron arrangement around the atom. If the atom can donate an electron pair (for example has lone pairs) then it is a lewis base. If the atom is likely to gain electrons, then it is a lewis acid.
by Emma Popescu 1L
Fri Nov 29, 2019 9:30 pm
Forum: Conjugate Acids & Bases
Topic: Delocalization of charge and stability
Replies: 4
Views: 385

Re: Delocalization of charge and stability

Does it say this in the textbook or did Dr. Lavelle mention it in lecture? If it is in the textbook, what page?
by Emma Popescu 1L
Fri Nov 29, 2019 9:26 pm
Forum: Conjugate Acids & Bases
Topic: NH3, acid or base?
Replies: 12
Views: 518

Re: NH3, acid or base?

Ammonia is a weak base. It reacts with water to produce ammonium ions and hydroxide ions.
by Emma Popescu 1L
Fri Nov 29, 2019 9:20 pm
Forum: Calculating the pH of Salt Solutions
Topic: pH vs. pOH
Replies: 17
Views: 125

Re: pH vs. pOH

If you have the pH of a solution, you can calculate its pOH or vice versa. For example, if the pH is 2 then the pOH will be 14-2=12
by Emma Popescu 1L
Fri Nov 22, 2019 8:13 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: Ionic
Replies: 6
Views: 29

Re: Ionic

Intramolecular forces are the forces that hold atoms together within a molecule (covalent, ionic bonds). Intermolecular forces are forces that exist between molecules (dipole-dipole, hydrogen bonding, London dispersion interactions).
by Emma Popescu 1L
Fri Nov 22, 2019 8:05 pm
Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
Topic: london forces
Replies: 9
Views: 42

Re: london forces

The molecule with the highest molar mass (and so size and number of electrons) has the highest polarisability so the electrons in the electron cloud can easily be distorted so it has the strongest london dispersion interactions.
by Emma Popescu 1L
Fri Nov 22, 2019 8:01 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar vs. Nonpolar
Replies: 6
Views: 64

Re: Polar vs. Nonpolar

I understand that CH2Cl2 is polar because a tetrahedral shape isn't completely symmetrical. However if a shape is symmetrical like a square planar would it be considered nonpolar? For example if it was a square planar with two Cl and two H atoms around a central atom, would it be considered non pol...
by Emma Popescu 1L
Fri Nov 22, 2019 7:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 7
Views: 62

Re: Polarity

A non polar molecule can have polar bonds. If the VSEPR shape is symmetrical, the dipoles can cancel out making the molecule non-polar.
by Emma Popescu 1L
Fri Nov 22, 2019 7:56 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: polar vs non polar
Replies: 6
Views: 40

Re: polar vs non polar

Victoria Otuya 4F wrote:Does a non-polar molecule mean it has a Dipole-Dipole intermolecular force?


A polar molecule has dipole-dipole interactions. A non-polar molecule has London dispersion interactions (induced-dipole induced-dipole)
by Emma Popescu 1L
Sat Nov 16, 2019 5:57 pm
Forum: Bond Lengths & Energies
Topic: bond lengths
Replies: 3
Views: 26

Re: bond lengths

Bond length is determined by the strength of the bond so the stronger the bond, the shorter the length. Single bond is the longest, then double bond and triple bond is the shortest. However, the size of the atom can determine the length of the single bond.
by Emma Popescu 1L
Sat Nov 16, 2019 5:50 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Melting Points
Replies: 7
Views: 38

Re: Melting Points

You should be able to assume the which molecule would have a higher or lower melting point based on their shape and strength of interactions/bonds.
by Emma Popescu 1L
Sat Nov 16, 2019 5:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR and Polarity
Replies: 4
Views: 23

Re: VSEPR and Polarity

If one atom is more electronegative than the other, there will be a dipole moment. Although the bonds are polar, the molecule will not if the shape is symmetrical causing the dipoles to cancel out.
by Emma Popescu 1L
Sat Nov 16, 2019 5:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion
Replies: 3
Views: 35

Re: Repulsion

I think we just need to know the number of regions of electrons dedicates the shape and Lone pair>triple>double>single bonds in terms of repulsion.
by Emma Popescu 1L
Sat Nov 16, 2019 5:36 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Hydrogen Bonding
Replies: 6
Views: 32

Re: Hydrogen Bonding

Hydrogen bonding is a special type of Dipole-Dipole as it is considered stronger than a regular dipole-dipole force.
by Emma Popescu 1L
Fri Nov 08, 2019 7:12 pm
Forum: Electronegativity
Topic: memorizing tables
Replies: 9
Views: 41

Re: memorizing tables

You do not need need to memorise any values for electronegativity. The only thing you need to know is the trend across a period and down the group in order to be able to assume which element is more/less electronegative than another.
by Emma Popescu 1L
Fri Nov 08, 2019 7:04 pm
Forum: Lewis Structures
Topic: Formal Charges
Replies: 15
Views: 65

Re: Formal Charges

505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?


You can break the octet rule only if the element can hold more than 8 electrons (starting 3p)
by Emma Popescu 1L
Fri Nov 08, 2019 6:59 pm
Forum: Dipole Moments
Topic: Dipole Moments
Replies: 5
Views: 55

Re: Dipole Moments

Dipole moments occur because of a separation of charge (caused by a difference in electronegativity). The more electronegative element has the greater share of the electrons than less electronegative element causing it to have a net negative charge. The larger the difference in electronegativity, th...
by Emma Popescu 1L
Fri Nov 08, 2019 6:54 pm
Forum: Dipole Moments
Topic: Relationship with Boiling Point and Shape
Replies: 2
Views: 20

Re: Relationship with Boiling Point and Shape

Branched molecules will have a lower boiling point than straight chain molecules because the intermolecular forces are reduced.
by Emma Popescu 1L
Fri Nov 08, 2019 6:48 pm
Forum: Bond Lengths & Energies
Topic: dissociation energy
Replies: 5
Views: 25

Re: dissociation energy

Dissociation energy is based on bond strength. The shorter the bond, the stronger it is resulting in a higher dissociation energy. For example, triple bonds have the highest dissociating energy and single bonds have the lowest.
by Emma Popescu 1L
Fri Nov 08, 2019 6:45 pm
Forum: Bond Lengths & Energies
Topic: bond length rules
Replies: 2
Views: 18

Re: bond length rules

There are no exceptions: single bond (longest) > double bond > triple bond (shortest) except for resonance structures in which the electrons are delocalised across all bonds.
by Emma Popescu 1L
Fri Nov 08, 2019 6:41 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Showing Work
Replies: 6
Views: 42

Re: Showing Work

You don't need to show the calculation for formal charge as most people directly use the shortcut, but showing work can give you some marks incase you make a calculation error.
by Emma Popescu 1L
Fri Nov 01, 2019 10:52 pm
Forum: *Particle in a Box
Topic: Topic 1C
Replies: 3
Views: 43

Re: Topic 1C

I don't think we need to know the material from Topic 1C. He did not talk about most of the information from that section.
by Emma Popescu 1L
Fri Nov 01, 2019 10:50 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: 1 B27
Replies: 5
Views: 95

Re: 1 B27

I am confused as to why we use 5 as the uncertainty in velocity. Aren't we suppose to use 10 as it is +-5m/s?
by Emma Popescu 1L
Fri Nov 01, 2019 10:46 pm
Forum: *Shrodinger Equation
Topic: Schrodinger's equation
Replies: 2
Views: 54

Re: Schrodinger's equation

A wavefunction is a mathematical function with values that vary with position. It can give the probability of finding the particle in a region proporitional to the value of the wavefunction squared in that region. Schrodinger's equation is used to calculate the wavefunction for any particle.
by Emma Popescu 1L
Fri Nov 01, 2019 10:42 pm
Forum: *Shrodinger Equation
Topic: wave function
Replies: 3
Views: 42

Re: wave function

No, Dr. Lavelle said to omit Topic 1C from the textbook.
by Emma Popescu 1L
Fri Nov 01, 2019 10:40 pm
Forum: *Shrodinger Equation
Topic: shrodinger equation
Replies: 4
Views: 59

Re: shrodinger equation

The Schrodinger equation is used to calculate both the wavefunction and the corresponding energy. There is a lot of information about it in Topic 1C in the textbook but we do not need to read that section.
by Emma Popescu 1L
Fri Nov 01, 2019 10:33 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Work function units
Replies: 5
Views: 38

Re: Work function units

Yes, the work function should always be in Joules so the units can later cancel out
by Emma Popescu 1L
Wed Oct 23, 2019 11:34 am
Forum: Trends in The Periodic Table
Topic: Electron Affinity Trends
Replies: 5
Views: 41

Re: Electron Affinity Trends

As you go down a group, electron affinity decreases as there is more shielding which decreases the electrostatic attraction between the nucleus and electrons, resulting in less energy released when e- is added to a gas phase atom. However, as you move across the period, electron affinity increases a...
by Emma Popescu 1L
Wed Oct 23, 2019 11:28 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Writing Electron Configurations Help
Replies: 3
Views: 31

Re: Writing Electron Configurations Help

This confused me as well and I am not sure about the textbook. However, in a test the electron configuration should definitely be written from lowest to highest energy level.
by Emma Popescu 1L
Wed Oct 23, 2019 11:22 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 4s and 3d
Replies: 5
Views: 41

Re: 4s and 3d

The 4s is filled first because it is at a lower energy than 3d. However, Dr. Lavelle wants us to put them from lowest to highest energy level (3d and then 4s) because 4s is ionized first.
by Emma Popescu 1L
Wed Oct 23, 2019 11:13 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Exceptions to Electron Configurations
Replies: 3
Views: 39

Re: Exceptions to Electron Configurations

Cu and Cr are only one electron away from being in a more stable state. A completely full or half full d sub-level is more stable than a partially filled d sub-level.
by Emma Popescu 1L
Thu Oct 17, 2019 1:12 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Atomic Radius
Replies: 18
Views: 116

Re: Atomic Radius

We won't need to calculate the value of atomic radius. If needed, the values should be given to us.
by Emma Popescu 1L
Thu Oct 17, 2019 1:04 am
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron configurations
Replies: 2
Views: 32

Re: Electron configurations

3d has lower energy when 4s is filled. You should list them in order of energy level
by Emma Popescu 1L
Thu Oct 17, 2019 12:53 am
Forum: Properties of Light
Topic: How does light have momentum but we assume it has no mass?
Replies: 4
Views: 38

Re: How does light have momentum but we assume it has no mass?

Light does have momentum however the equation m*v cannot be used in this case to calculate momentum
by Emma Popescu 1L
Thu Oct 17, 2019 12:41 am
Forum: Significant Figures
Topic: Tests and Significant Figures
Replies: 6
Views: 72

Re: Tests and Significant Figures

They remove points on tests if the answer does not include the correct number of significant figures (more or less).
by Emma Popescu 1L
Thu Oct 17, 2019 12:36 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test 1 [ENDORSED]
Replies: 107
Views: 2751

Re: Test 1 [ENDORSED]

DesireBrown3K wrote:Would we be able to go to office hours and review our test with a TA for any problems we got incorrect?


Yes, our TA said to come to office hours if we have questions about the test
by Emma Popescu 1L
Wed Oct 09, 2019 11:17 am
Forum: Limiting Reactant Calculations
Topic: M.9 hw prob
Replies: 4
Views: 55

Re: M.9 hw prob

The net ionic equation only lists the species participating in the reaction. We should learn it later in the course so don't worry too much about it for now.
by Emma Popescu 1L
Wed Oct 09, 2019 11:12 am
Forum: Molarity, Solutions, Dilutions
Topic: Polyatomic ions on Test 1
Replies: 4
Views: 70

Re: Polyatomic ions on Test 1

The test will provide the chemical formula or equation so we don't need to know polyatomic ions for this test
by Emma Popescu 1L
Wed Oct 09, 2019 11:09 am
Forum: Molarity, Solutions, Dilutions
Topic: E.9
Replies: 3
Views: 75

Re: E.9

My TA said we will go over writing formulas later in the course and for now they will provide the formulas on the test.
by Emma Popescu 1L
Wed Oct 09, 2019 11:06 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Test Equation Sheet
Replies: 8
Views: 67

Re: Test Equation Sheet

They include basic equations and unit conversions
by Emma Popescu 1L
Wed Oct 09, 2019 11:02 am
Forum: Significant Figures
Topic: Significant Figures for Test 1
Replies: 3
Views: 51

Re: Significant Figures for Test 1

My TA said that they are not very strict regarding significant figures on tests
by Emma Popescu 1L
Wed Oct 09, 2019 10:59 am
Forum: Administrative Questions and Class Announcements
Topic: Week 2 Homework Problems [ENDORSED]
Replies: 67
Views: 1596

Re: Week 2 Homework Problems [ENDORSED]

Maya Pakulski 3D wrote:
Jaklin Astvatsatryan 3G wrote:
Lauren Sanchez 3D wrote:Just to make sure, the homework problems are now due during our actual discussions right?


Yes. Our TA's will be collecting them the day of your discussion.


Our answers on chemistry community will always be due Sunday night though right?


yes, the 5 posts on chemistry community are due Sunday
by Emma Popescu 1L
Wed Oct 02, 2019 11:12 am
Forum: Limiting Reactant Calculations
Topic: Question about E9 [ENDORSED]
Replies: 3
Views: 80

Re: Question about E9 [ENDORSED]

Our TA said we shouldn't worry about that until chemistry 14B as they will usually give as the formula
by Emma Popescu 1L
Wed Oct 02, 2019 11:07 am
Forum: Empirical & Molecular Formulas
Topic: Homework problem E1
Replies: 9
Views: 84

Homework problem E1

Could someone please exercise E1. I looked at the solutions but I am still a bit confused.
by Emma Popescu 1L
Wed Oct 02, 2019 9:30 am
Forum: Balancing Chemical Reactions
Topic: Naming ionic/ molecular compounds
Replies: 7
Views: 95

Re: Naming ionic/ molecular compounds

Our TA said we shouldn't worry about that until Chem 14B and that we will go over it later on
by Emma Popescu 1L
Wed Oct 02, 2019 9:26 am
Forum: Limiting Reactant Calculations
Topic: Homework for week 2 [ENDORSED]
Replies: 3
Views: 43

Re: Homework for week 2 [ENDORSED]

Homework is always due during discussions except for week 1.
by Emma Popescu 1L
Wed Oct 02, 2019 9:24 am
Forum: SI Units, Unit Conversions
Topic: Question about Showing Work
Replies: 22
Views: 207

Re: Question about Showing Work

I think they give partial credit for showing work but it does not necessarily need to be very detailed. It will also help to get follow through points in case you made a mistake along the way but your method is correct. As long as they understand what you are doing and you get the correct answer, yo...
by Emma Popescu 1L
Wed Oct 02, 2019 9:12 am
Forum: Significant Figures
Topic: General Rules to Help with Sig Figs
Replies: 18
Views: 197

Re: General Rules to Help with Sig Figs

Will we be penalized if we use more significant figures than needed?

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