Search found 61 matches

by Katelyn Phan 2A
Sat Mar 16, 2019 12:02 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: K'
Replies: 4
Views: 68

Re: K'

It is a usual rate to understand in order to solve using the pre-equilibrium method!
by Katelyn Phan 2A
Sun Mar 10, 2019 11:08 pm
Forum: Second Order Reactions
Topic: Temperature
Replies: 6
Views: 81

Re: Temperature

The rate constant can change according to temperature. If you increase the temperature, you increase the rate.
by Katelyn Phan 2A
Sun Mar 10, 2019 11:05 pm
Forum: Second Order Reactions
Topic: Slope
Replies: 2
Views: 43

Re: Slope

Like stated above, the slope is based off the change in concentration over time. As time increases, the concentration decreases. In a first order reaction, the y-axis is ln[A] thus as A decreases as time increases, ln[A] will also decrease. Thus creating a negative slope. However for a second order,...
by Katelyn Phan 2A
Sun Mar 10, 2019 10:59 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: molecularity
Replies: 8
Views: 89

Re: molecularity

The molecularity is based on the number of particles/molecules that will collide simultaneously as this reaction occurs. It's based on the number of species.
by Katelyn Phan 2A
Sun Mar 10, 2019 10:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reactions with Multiple Reactants
Replies: 3
Views: 52

Re: Reactions with Multiple Reactants

Yes, this is so we can do simply calculations. Therefore, we assume that there's excess/large quantity of the other reactants such that their concentration is insignificant to the rate.
by Katelyn Phan 2A
Sun Mar 10, 2019 10:56 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: rate determining
Replies: 3
Views: 41

Re: rate determining

As stated above it would be the slowest step because it would add the most to the reaction rate.
by Katelyn Phan 2A
Sat Feb 23, 2019 7:49 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic Cell Diagram
Replies: 6
Views: 81

Re: Galvanic Cell Diagram

I believe its good have an understanding of how it works, how the charges flow, and be able to visualize what the cell looks like based on the cell diagram given.
by Katelyn Phan 2A
Sat Feb 23, 2019 7:47 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Faradays Constant
Replies: 4
Views: 69

Re: Faradays Constant

Faradays constant is the "F" in the equation. It's units will help cancel out the others to leave you with units of energy!
by Katelyn Phan 2A
Sat Feb 23, 2019 7:45 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: -charge x E = Wmax
Replies: 2
Views: 58

Re: -charge x E = Wmax

Its negative because the system is doing work. Had the system have work done on it, it would have a positive charge.
by Katelyn Phan 2A
Sat Feb 23, 2019 7:44 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.9 6th Edition
Replies: 2
Views: 50

Re: 14.9 6th Edition

You'll be able to find the number of moles transferred by balancing the equation through separating the half reactions.
by Katelyn Phan 2A
Sat Feb 23, 2019 7:41 pm
Forum: Balancing Redox Reactions
Topic: Oxidating/Reducing AGENTS
Replies: 6
Views: 71

Re: Oxidating/Reducing AGENTS

The oxidizing agent was reduced and it oxidizes the reducing agent. Vice versa. The oxidizing agent gain in electron which means it took a electron from the reducing agent.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:16 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: why is H negative when calculating S?
Replies: 4
Views: 74

Re: why is H negative when calculating S?

Freezing is an exothermic process, thus the transfer of energy is released.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:15 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: DeltaS=kBlnW
Replies: 3
Views: 63

Re: DeltaS=kBlnW

This equation is used to calculate residual entropy on a microscopic level. It refers to W, (the number of micro-states it may take)^ # of particles. Kb is Boltzmann's constant given on the formula sheet.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:13 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Cv/Cp versus R
Replies: 4
Views: 89

Re: Cv/Cp versus R

R is used in isothermal reactions whereas 3/2R and 5/2R are used in place of Cp or Cv where there is a temperature change.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:11 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Ideal Behavior
Replies: 3
Views: 99

Re: Ideal Behavior

chloewinnett1L wrote:I was going to ask the same thing, should we always take "ideal conditions" to mean 1 mol of gas and pressure=1 atm?


If not stated otherwise, then such assumption would be sufficient.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:09 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Change in reversible reaction
Replies: 3
Views: 68

Re: Entropy Change in reversible reaction

The total entropy change does not equal 0 under such conditions. It is the change in internal energy that equals 0.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:08 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Converting Celsius to Kelvin
Replies: 7
Views: 100

Re: Converting Celsius to Kelvin

273 K should be fine. It also helps if you look at the overall sig figs required for the specific condition.
by Katelyn Phan 2A
Mon Feb 11, 2019 9:07 am
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 10
Views: 163

Re: Reversible vs Irreversible

Usually it would be told whether or not the system is reversible or irreversible.
by Katelyn Phan 2A
Sun Feb 03, 2019 5:02 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 1st law of thermodynamics
Replies: 7
Views: 119

Re: 1st law of thermodynamics

Since all matter can not be created nor destroyed, all the internal energy of an isolated system will remain constant.
by Katelyn Phan 2A
Sun Feb 03, 2019 5:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 3 methods for enthalpy calculation
Replies: 10
Views: 149

Re: 3 methods for enthalpy calculation

The most effective method would be based on the conditions given. The only difference is the accuracy and reliance of the method.
by Katelyn Phan 2A
Sun Feb 03, 2019 5:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated System
Replies: 5
Views: 370

Re: Isolated System

ΔU is zero because it can't be heated and no material can be added. Therefore, there's no work nor is there q.
by Katelyn Phan 2A
Sun Feb 03, 2019 4:57 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: open system
Replies: 8
Views: 131

Re: open system

The constant pressure exerted onto the beaker is the atmospheric pressure which is much larger than any pressure that the system exerts on the surroundings.
by Katelyn Phan 2A
Fri Jan 25, 2019 6:52 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Solving bond enthalpies
Replies: 3
Views: 51

Re: Solving bond enthalpies

When you break a bond, you require energy. (+) On the other hand, when a bond is formed, energy is released. (-)
by Katelyn Phan 2A
Fri Jan 25, 2019 6:51 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 51

Re: Hess's Law

Hess's Law is taught in Chem 14B like stated above. It's used to calculate the total enthalpy of the rxn using the separate enthalpies of rxns in between.
by Katelyn Phan 2A
Fri Jan 25, 2019 6:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 3
Views: 62

Re: 3 Methods

The general reason is because the bond enthalpies for molecules that are not diatomic are averages depending on the different molecules they occur in.
by Katelyn Phan 2A
Sat Jan 19, 2019 5:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka vs. Kb
Replies: 12
Views: 264

Re: Ka vs. Kb

Ka is used for acids and Kb is used for bases. You can also determine the Ka based on knowing the Kb and vice versa.
by Katelyn Phan 2A
Sat Jan 19, 2019 5:51 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: exothermic/endothermic
Replies: 3
Views: 89

Re: exothermic/endothermic

You can determine it based on the sign of delta h (enthalpy). You can also tell from the description of the reaction; whether or not energy is required or released.
by Katelyn Phan 2A
Sat Jan 19, 2019 5:49 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas added
Replies: 4
Views: 69

Re: Inert Gas added

The inert gas will not have any effect on the equilibrium system. Since it doesn't react, it won't change.
by Katelyn Phan 2A
Thu Jan 10, 2019 1:51 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Finding K in 5I.7
Replies: 3
Views: 60

Re: Finding K in 5I.7

From what I know,we would be expected to know the method taught during lecture and in the modules for now.
by Katelyn Phan 2A
Thu Jan 10, 2019 1:50 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: The relationship between Kc and K
Replies: 2
Views: 57

Re: The relationship between Kc and K

Its not that Kc is greater or less than K, but it is greater or less than Q. K is used in terms of equilibrium. On the other hand Q is used at any time during the reaction. When the mols of reactants are greater than those of products, the reaction proceed forward in order to create more products fo...
by Katelyn Phan 2A
Thu Jan 10, 2019 1:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Giving Qc or Qp when asked for Q
Replies: 5
Views: 78

Re: Giving Qc or Qp when asked for Q

This depends on the given information. If you are given units of concentration then use Qc (if they give you the grams and liters this applies too) but if you're given units of pressure then use Qp!
by Katelyn Phan 2A
Sat Dec 08, 2018 10:04 pm
Forum: Calculating the pH of Salt Solutions
Topic: Atoms that don't affect pH
Replies: 3
Views: 172

Re: Atoms that don't affect pH

Atoms that don't contribute to the creation of OH- or H3O+ are spectator ions and will not affect the pH.
by Katelyn Phan 2A
Thu Nov 29, 2018 1:49 pm
Forum: Biological Examples
Topic: acids
Replies: 5
Views: 80

Re: acids

The digestive system contains buffers which will increase the pH of acids to a safe level. On the other hand when acids enter cuts they burn since cellular/atomic level destruction breakdown occurs. There are no protective buffers in these locations that can dilute the pH acidity level to neutral nu...
by Katelyn Phan 2A
Thu Nov 29, 2018 1:47 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Cis and Trans
Replies: 10
Views: 169

Re: Cis and Trans

There's no definite answer to which is better. The preferred version depends on the purpose of the molecule. The situation at hand will determine the more desired form between the two.
by Katelyn Phan 2A
Thu Nov 29, 2018 1:44 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number
Replies: 10
Views: 142

Re: Coordination Number

The coordination number of transition metals can be calculated by knowing the overall charges of the compound and the individual charges of non-metals in the compound. The charges of all atoms within the compound should add up to the overall charge of the compound.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:51 am
Forum: Hybridization
Topic: S-Character Bond Angle Trend
Replies: 3
Views: 51

Re: S-Character Bond Angle Trend

With greater regions of electron density comes smaller bond angles.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:46 am
Forum: Hybridization
Topic: double bonds
Replies: 14
Views: 191

Re: double bonds

Double bonds consist of one pi and one sigma bond because the orientation of a double bond consists of a both a side to side overlap as well as a end-to-end overlap. When you continue to add bonds, you'll add another pi bond since there is now another side-to-side overlap.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:42 am
Forum: Hybridization
Topic: Octet Expansion and d-Orbitals
Replies: 8
Views: 163

Re: Octet Expansion and d-Orbitals

So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule? Under my current understanding, I believe any element in the first three groups don't have to meet the octet rule of maximum 8 electrons, it can exceed the octet rule since it has access to th...
by Katelyn Phan 2A
Sat Nov 24, 2018 10:39 am
Forum: Hybridization
Topic: Writing out Hybridization
Replies: 8
Views: 95

Re: Writing out Hybridization

Either order works. The book tends to write it with the d-orbital first, however you can write it afterwards as well.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:37 am
Forum: Hybridization
Topic: determining shape from given information
Replies: 3
Views: 56

Re: determining shape from given information

No, hybridization only tells us the number of regions of electron density around the central atom. It doesn't tell us the specific bonds/pairs around it. (bonded or lone)
by Katelyn Phan 2A
Sat Nov 24, 2018 10:36 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Drawing Structures on Test
Replies: 11
Views: 161

Re: Drawing Structures on Test

According to what was stated in class, you'll only be really expected to draw the lewis structure and determine the name of the shape.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:33 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Sixth Edition. Question 4.109
Replies: 4
Views: 67

Re: Sixth Edition. Question 4.109

Great question! Though not drawn, it is assumed that there are two lone pairs attached to oxygen to complete the octet. Therefore there's a total of 4 regions of electron density. The lone pairs repel each other and the bonded pairs thus creating a bent shape. This has the bond angle of 109.5.
by Katelyn Phan 2A
Sat Nov 24, 2018 10:30 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs on the Central Atom
Replies: 5
Views: 97

Re: Lone Pairs on the Central Atom

Lone pairs do a play a major role in determining the shape. The repulsion of lone pairs is even stronger than those of bonded pairs. It will push the bonded pairs away. However, the actual shape does not take lone pairs in consideration. You name the shape based off the location of bonded pairs that...
by Katelyn Phan 2A
Mon Nov 12, 2018 10:40 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angles
Replies: 3
Views: 58

Re: Bond angles

You would know the bond angles from knowing the shape based on electron repulsion. The number of pairs around the central atom will repel one another creating semi-symmetric bond angles. This is based on the angle that allows the electrons to be as far as possible away from others.
by Katelyn Phan 2A
Mon Nov 12, 2018 10:37 am
Forum: Determining Molecular Shape (VSEPR)
Topic: How do you utilize the VSEPR model?
Replies: 4
Views: 60

Re: How do you utilize the VSEPR model?

The VSEPR theory is a method in order to identify the shape of a molecule. This is determined based off the number of lone pairs and bonded pairs on the central atom. These characteristics are linked to a specific shape identified by the VSEPR Theory.
by Katelyn Phan 2A
Mon Nov 12, 2018 10:35 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Chapter 4 Homework Number 1
Replies: 6
Views: 95

Re: Chapter 4 Homework Number 1

The bond angles will change according to the presence of electrons. This is due to the concept of electron repulsion (negatives repel negatives).
by Katelyn Phan 2A
Mon Nov 05, 2018 9:49 am
Forum: Electronegativity
Topic: Periodic Trends
Replies: 10
Views: 235

Re: Periodic Trends

Without considering exceptions, I like to think the trend from least to greatest.
For size you have increasing going left and down.
and almost anything else (ionization energy, electronegativity, etc.) is increasing going up and right.
by Katelyn Phan 2A
Mon Nov 05, 2018 9:45 am
Forum: Resonance Structures
Topic: Resonance with formal charge
Replies: 6
Views: 196

Re: Resonance with formal charge

The resonance of a structure will not change the FC.
by Katelyn Phan 2A
Mon Nov 05, 2018 9:44 am
Forum: Octet Exceptions
Topic: Radicals
Replies: 16
Views: 413

Re: Radicals

The radical is placed with the atom based on the formal charge. Remember that we want a FC closer to 0.
by Katelyn Phan 2A
Mon Nov 05, 2018 9:41 am
Forum: Formal Charge and Oxidation Numbers
Topic: Formal Charge Equation
Replies: 13
Views: 2539

Re: Formal Charge Equation

An easier way to look at the equation is:
FC = Valence electrons - (line + dots)

lines being the bonds
dots being the individuals in lone pairs
by Katelyn Phan 2A
Fri Oct 26, 2018 1:03 pm
Forum: Lewis Structures
Topic: Lewis Dot Order
Replies: 10
Views: 83

Re: Lewis Dot Order

Like stated above, there is no particular order; however, you should consider symmetry.
by Katelyn Phan 2A
Fri Oct 26, 2018 1:00 pm
Forum: Trends in The Periodic Table
Topic: Removing 2nd Electron
Replies: 9
Views: 162

Re: Removing 2nd Electron

The second ionization energy is always greater than the first since the pull of the positive protons int he nucleus is much greater.
by Katelyn Phan 2A
Fri Oct 26, 2018 12:58 pm
Forum: Trends in The Periodic Table
Topic: Atomic, Covalent, and Ionic Radius
Replies: 5
Views: 97

Re: Atomic, Covalent, and Ionic Radius

haleyervin7 wrote:How will we know if something is ionically or covalently bonded?


In a covelant bond, you would share electrons. This often occurs between two non-metals due to their high ionization energy.
On the other, ionic bonds are between a metal and a nonmetal where there is a transfer of electrons instead.
by Katelyn Phan 2A
Sat Oct 20, 2018 11:13 pm
Forum: Quantum Numbers and The H-Atom
Topic: Lyman, Balmer, Pascal
Replies: 10
Views: 330

Re: Lyman, Balmer, Pascal

Lynsea_Southwick_3F wrote:Would n never equal 4 or anything more then 3?


There are energy levels greater than 4. Electrons are not limited to only 4 states of energy.
by Katelyn Phan 2A
Sat Oct 20, 2018 11:10 pm
Forum: Quantum Numbers and The H-Atom
Topic: HW 2.19
Replies: 3
Views: 84

Re: HW 2.19

Your calculations are correct! The issue may be in the Textbook version you're using. It may not be corresponding (in edition) with your solution manual. Based off the 6th edition, (b) asks about the 6-d subshell and (c) 3-p subshell. These situations align with the solution manual you are using. Ho...
by Katelyn Phan 2A
Thu Oct 11, 2018 3:10 pm
Forum: Properties of Light
Topic: Photoelectric effect
Replies: 4
Views: 44

Re: Photoelectric effect

The energy of each photon does not necessarily have to be greater. It needs to reach a certain level of energy to remove an electron. That fence it needs to climb over would be the threshold or work energy.
by Katelyn Phan 2A
Thu Oct 11, 2018 3:08 pm
Forum: Properties of Light
Topic: Balmer series vs Lyman series
Replies: 4
Views: 66

Re: Balmer series vs Lyman series

That would be based on which energy level the electron is currently at and where it's going to go. The Lyman series is based on Ultraviolet light which entitles a larger change in energy from level 1. On the other hand, the Balmer series are frequency and wavelengths relevant to Visible light and le...
by Katelyn Phan 2A
Thu Oct 11, 2018 3:04 pm
Forum: Properties of Light
Topic: Why Short Wavelengths Can Eject e-
Replies: 6
Views: 107

Re: Why Short Wavelengths Can Eject e-

It's a general concept that as frequency increases, wavelength decreases. Frequency is inversely proportional to energy per photon. In the case of attempting to emit electrons from metal surfaces, you would need a specific frequency corresponding to energy. Rather than looking at the wavelength, its...
by Katelyn Phan 2A
Mon Oct 01, 2018 8:52 pm
Forum: Molarity, Solutions, Dilutions
Topic: Study Module Post-assessment Question
Replies: 5
Views: 162

Re: Study Module Post-assessment Question

I am confused on this problem as well. I'm unsure of what the initial and final volumes are. I used the 15L as the initial volume and when it came to the final volume I was not sure whether to use the 0.02L or 0.250L. The final volume would be .250 ml since it's what you're transferring and attempt...
by Katelyn Phan 2A
Mon Oct 01, 2018 8:35 pm
Forum: Limiting Reactant Calculations
Topic: Percent yield
Replies: 10
Views: 230

Re: Percent yield

The actual percent yield would be given like how molar mass of a compound would need to be given in order to further advance calculations. :)
by Katelyn Phan 2A
Mon Oct 01, 2018 8:34 pm
Forum: SI Units, Unit Conversions
Topic: Naming Compounds
Replies: 8
Views: 223

Re: Naming Compounds

With calcium sulfide and it's chemical notation, you could recognize the bond between the two elements. The -ide contributes to the fact that it is indeed an ionic compound. Calcium has a charge of +2 and sulfur has a charge of -2; therefore, the notation would be CaS. The quickest way to figure it ...

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