Search found 85 matches

by melissa_dis4K
Wed Feb 13, 2019 9:31 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U equal to zero
Replies: 2
Views: 12

Delta U equal to zero

Is delta U equal to zero for irreversible processes?
by melissa_dis4K
Wed Feb 13, 2019 1:02 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Hotdog #5
Replies: 4
Views: 37

Re: Hotdog #5

How is the pressure changing?
by melissa_dis4K
Wed Feb 13, 2019 12:57 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Entropy at 0 K
Replies: 2
Views: 16

Entropy at 0 K

Can someone please explain why molecules do have entropy at 0 Kelvin and what that entropy is? Thank you!
by melissa_dis4K
Wed Feb 13, 2019 12:52 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: hotdog #5c
Replies: 1
Views: 13

hotdog #5c

How can we calculate the entropy of vaporization for water at room temperature?
by melissa_dis4K
Wed Feb 13, 2019 12:45 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Hotdog #5
Replies: 4
Views: 37

Hotdog #5

Why do we use constant volume heat capacity instead of constant pressure? Isn't the volume changing? Thanks
by melissa_dis4K
Tue Feb 12, 2019 4:58 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Problem 9.13 6th edition
Replies: 1
Views: 24

Problem 9.13 6th edition

During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 C was compressed suddenly (and irreversibly) to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 C. Assume ideal behavior. What is the change in entropy of the gas? So I know ...
by melissa_dis4K
Tue Feb 12, 2019 12:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Delta U
Replies: 1
Views: 10

Delta U

I know that for a reversible, isothermic process delta U is zero because there is no change in temperature. Is delta U =zero for irreversible process as well? And if so, why? Thank you!
by melissa_dis4K
Thu Feb 07, 2019 1:35 pm
Forum: Bronsted Acids & Bases
Topic: Weak Acids
Replies: 1
Views: 12

Weak Acids

Why do weak acids have to go in the forward direction?
by melissa_dis4K
Thu Feb 07, 2019 1:17 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Taking into account 10^-7 [H3O+]
Replies: 1
Views: 7

Taking into account 10^-7 [H3O+]

In class, Professor Lavelle said that there are times when we need to take into account that 10^-7 [H3O+] but other times it is negligible. I am confused on what he meant and when we do take it into account. Thank you!
by melissa_dis4K
Thu Feb 07, 2019 1:07 pm
Forum: Bronsted Acids & Bases
Topic: CH3COOH acid/base identifying
Replies: 1
Views: 9

CH3COOH acid/base identifying

How can I know that CH3COOH wants to donate its proton to create H3O+ and CH3COO- without memorizing that it is an acid from the table in the book? I want to know how to identify them so I can write chemical equations when needed to do ICE tables for weak acids and bases. Thank you? Also will it alw...
by melissa_dis4K
Thu Jan 31, 2019 9:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bonds and energy release
Replies: 2
Views: 22

Re: Bonds and energy release

When a bond is broken, energy is required. When a bond is formed energy is released.
Breaking Bonds → Energy Absorbed
Forming Bonds → Energy Released
by melissa_dis4K
Thu Jan 31, 2019 8:31 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Work
Replies: 3
Views: 28

Work

How can you determine whether work was done by or on a system? Thank you.
by melissa_dis4K
Thu Jan 31, 2019 8:24 pm
Forum: Calculating Work of Expansion
Topic: Work
Replies: 5
Views: 34

Work

How do you know when work is positive or negative. I know that when F and displacement are in the same direction work is positive but in the homework 8.3b.) 6th edition I got confused. Thanks!
by melissa_dis4K
Fri Jan 25, 2019 10:36 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Change in temp
Replies: 3
Views: 23

Change in temp

I am confused on increasing and decreasing the temperature of an endothermic reaction. Why does decreasing the temperature favor the reactant? I thought that it always favored the endothermic (requiring heat) reaction.
by melissa_dis4K
Thu Jan 24, 2019 4:32 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 109
Views: 2472

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

On worksheet 1 how exactly did they get the answer for number 3 because I am confused. I just thought it was Kc=[products]/[reactants] so Kc=x^5/1.0-x. Thank you
by melissa_dis4K
Thu Jan 24, 2019 4:08 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 109
Views: 2472

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

Can someone please explain why we need to square the Kc for worksheet 1 question #2a? I thought that the same molecules under the same conditions (same temp (973 K) would have the same Kc even if one has more "material" used. Why do I need to square it?
Thank you!
by melissa_dis4K
Thu Jan 24, 2019 3:55 pm
Forum: Administrative Questions and Class Announcements
Topic: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)
Replies: 109
Views: 2472

Re: DOWNLOAD SESSION WORKSHEETS HERE - Sun 7-9PM (Karen)

On Worksheet 2, why is the concentration of CO3 the same as Ka2 for problem 4b? In the second ICE table, the concentration of CO3 is x, and because x is so small, it is essentially Ka2.[/quote] I still don't understand this, I'm sorry could someone please explain more? I'd greatly appreciate it. Wh...
by melissa_dis4K
Tue Jan 22, 2019 9:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Autoprotolysis of water
Replies: 1
Views: 14

Autoprotolysis of water

How do you know when the autoprotolysis of water doesn't significantly affect the pH? Is this different for different acids and bases or should it always be assumed? Thanks!
by melissa_dis4K
Tue Jan 22, 2019 6:07 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: concentration of H3O and OH-
Replies: 1
Views: 26

concentration of H3O and OH-

How do I answer the following question. All I know is that Kw=[H3O+][OH-]
Estimate the concentrations of (a) [H3O+] and (b) [OH-] at 25 C in
6.0 x 10^-5 m HI(aq).
[Answer: (a) 60. mumol/L; (b) 0.17 nmol/L]
Thank you
by melissa_dis4K
Mon Jan 21, 2019 10:13 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: partial pressures vs. concentrations
Replies: 3
Views: 11

partial pressures vs. concentrations

I've noticed that when all the species are in the gas phase, the book has been using partial pressures and then converting them into concentrations using the ideal gas law and the ice table, so my question is when calculating the equilibrium constant for a reaction with all species in gas phase shou...
by melissa_dis4K
Mon Jan 21, 2019 9:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Finding temperature
Replies: 1
Views: 18

Finding temperature

For the following question how am I supposed to find the temperature to convert the given partialpressures into concentrations knowing that concentration= P/RT? Self-Test 11.10A The initial partial pressures of nitrogen and hydrogen in a rigid, sealed vessel are 0.010 and 0.020 bar, respectively. Th...
by melissa_dis4K
Mon Jan 21, 2019 3:59 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium costant
Replies: 2
Views: 16

Re: Equilibrium costant

I see.. thank you so much!
by melissa_dis4K
Mon Jan 21, 2019 3:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Net ionic equation
Replies: 2
Views: 17

Net ionic equation

Do we need to know how to write the equilibrium constant for net ionic equations? It is on the sixth edition, after Chapter 11.2 but under self assessment 11.3. Thank you!
by melissa_dis4K
Mon Jan 21, 2019 3:32 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium costant
Replies: 2
Views: 16

Equilibrium costant

In the following question I did not understand why they used both concentration and partial pressure for the equilibrium constant. I thought that you only used either concentrations or partial pressures, not both. Can someone explain to me please? This is from the sixth edition. Self-Test 11.2A Writ...
by melissa_dis4K
Sun Jan 20, 2019 10:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5%
Replies: 5
Views: 29

Re: 5%

In the 1/16/19 lecture, he explained towards the end that because x was less than 5% of the initial value it was okay, since in that calculation it was 1.3%. He got the 1.3% from calculating the % ionization of aceitic acid. I was also confused on what he meant but I think that he means that if the ...
by melissa_dis4K
Sun Jan 20, 2019 10:29 pm
Forum: Ideal Gases
Topic: ICE table
Replies: 10
Views: 51

ICE table

Are Ice tables only for molarity? Or can we use them for partial pressures as well? I saw a question on Chemistry community about using partial pressures in ICE table but I thought it was only used for molarity. Thank you!
by melissa_dis4K
Sun Jan 20, 2019 10:22 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Acids and Bases
Replies: 3
Views: 24

Acids and Bases

I am confused on how to identify an acid from a base and when it is best for it to gain/ get rid of its proton? Thank you.
by melissa_dis4K
Sat Jan 12, 2019 5:01 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Module 2
Replies: 3
Views: 502

Re: Module 2

I did the same thing as explained above and I get Kc=[BrCl]^2/[Br2][Cl2]=[3.37 x 10^-5]^2/[7.52 x 10^-5][7.52 x 10^-5].
My answer: 0.199637845, however, is not an answer choice can someone please explain what I did wrong?
Thank you!
by melissa_dis4K
Sat Jan 12, 2019 11:38 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium being shifted
Replies: 1
Views: 27

Equilibrium being shifted

So both in the module video and in class, Professor Lavelle mentioned that we should not think of equilibrium being shifted, rather that it sits on the right or left. However, when I was completing the first module I came across two questions: With respect to equilibrium constants what does it mean ...
by melissa_dis4K
Sat Jan 12, 2019 11:27 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constants
Replies: 2
Views: 25

Equilibrium constants

This is a question from the module, I just would like an explanation for why equilibrium constants are useful. I know that the equilibrium constant is equal to the [products]/[reactants]. But I don't understand what the answer would be if the choices are: A. One number that gives us information abou...
by melissa_dis4K
Sat Dec 08, 2018 7:27 pm
Forum: Bronsted Acids & Bases
Topic: KOH
Replies: 1
Views: 25

KOH

Can someone pls explain how to draw the Lewis structure for KOH and how to determine if its a bronsted acid or a base? Thanks!
by melissa_dis4K
Sat Dec 08, 2018 11:01 am
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 2
Views: 33

Re: Bronsted Acids and Bases

Would it be because it is already stable since the formal charge of Sulfur with the lone pair is 0?
by melissa_dis4K
Sat Dec 08, 2018 10:59 am
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 2
Views: 33

Bronsted Acids and Bases

Can someone pls explain how H2SO3 is a bronsted acid? I thought the sulfur could accept a proton with its lone pair making it a bronsted base but that is not correct. Thank you!
by melissa_dis4K
Sat Dec 08, 2018 10:55 am
Forum: Bronsted Acids & Bases
Topic: Bronsted acid
Replies: 4
Views: 38

Bronsted acid

Why is HBr a bronsted acid?
by melissa_dis4K
Sat Dec 08, 2018 12:29 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Angles
Replies: 2
Views: 27

Angles

Why does changing a hydrogen in CH4 to CH3F change the angle of the molecule? Is it because the F has lone pairs and repels the bonding pairs thus changing the angle?
by melissa_dis4K
Fri Dec 07, 2018 10:38 pm
Forum: Ionic & Covalent Bonds
Topic: Boiling point
Replies: 3
Views: 32

Boiling point

How can you determine which has a higher boiling point and why between C5H12 and C3H8? Thank you!
by melissa_dis4K
Fri Dec 07, 2018 10:20 pm
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 4
Views: 58

Re: Bronsted Acids and Bases

It's helpful to draw the lewis structures to see if the structure is stable enough to either donate or accept a hydrogen. For example, NH4+ is a base because it can only donate a hydrogen. If it accepted a hydrogen, Nitrogen would have 5 bonds, which we know is not possible. Another example is OH-....
by melissa_dis4K
Fri Dec 07, 2018 10:11 pm
Forum: Lewis Structures
Topic: Valence electrons
Replies: 2
Views: 22

Re: Valence electrons

Thanks!
by melissa_dis4K
Fri Dec 07, 2018 10:11 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shape
Replies: 3
Views: 22

Re: Molecular shape

Thank you! That makes sense, so to clarify the Pt is the central transition metal atom therefore I shouldn't have included it as a seventh ligand. I got confused because it was inside the brackets. May I ask what the Br3 is then?Is it just another molecule attaching to it not part of the coordinatio...
by melissa_dis4K
Fri Dec 07, 2018 10:07 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 5
Views: 29

Re: Electronegativity

When drawing lewis structures any negative charges should go on the most electronegative atom and I thought the negative charge should go on nitrogen rather than carbon.
by melissa_dis4K
Fri Dec 07, 2018 9:20 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 5
Views: 29

Electronegativity

Between carbon and nitrogen which is more electronegative? I thought it was Nitrogen but according to a review session I went to, it's actually carbon?
by melissa_dis4K
Fri Dec 07, 2018 1:24 am
Forum: Lewis Structures
Topic: Valence electrons
Replies: 2
Views: 22

Valence electrons

What are the valence electrons of elements in the d block?
by melissa_dis4K
Fri Dec 07, 2018 1:17 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Ch 17: Coordination Compounds worksheet [ENDORSED]
Replies: 1
Views: 54

Ch 17: Coordination Compounds worksheet [ENDORSED]

How does one solve this question can someone pls explain how there are 6 ligands? Vitamin B12 is an essential nutrient containing Cobalt (Co). Cyanocobalamin, shown at right, is one form of B12 in which the cobalt center has a cyanide ligand. In addition, the cobalt is coordinated by a ring structur...
by melissa_dis4K
Fri Dec 07, 2018 1:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular shape
Replies: 3
Views: 22

Molecular shape

To find the molecular shape of [Pt(NH3)5Cl]Br3 do I have to find the coordination number? And if so, isn't it 7? And the answer for this is octahedral does this mean that anything above 6 is octahedral? Or am I doing this wrong? Thanks!
by melissa_dis4K
Thu Dec 06, 2018 12:21 am
Forum: Bronsted Acids & Bases
Topic: Bronsted Acids and Bases
Replies: 4
Views: 58

Bronsted Acids and Bases

How do you know when the molecule is best accepting or donating its hydrogen?
by melissa_dis4K
Wed Dec 05, 2018 12:49 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 1
Views: 23

Electronegativity

Between atoms like chloride and oxygen how do you determine which has a higher electronegativity given that electronegativity increases as you go up and across to the right?
by melissa_dis4K
Wed Dec 05, 2018 12:49 pm
Forum: Electronegativity
Topic: Electronegativity
Replies: 2
Views: 23

Electronegativity

Between atoms like chloride and oxygen how do you determine which has a higher electronegativity given that electronegativity increases as you go up and across to the right?
by melissa_dis4K
Wed Dec 05, 2018 12:41 pm
Forum: Naming
Topic: Naming
Replies: 2
Views: 21

Naming

When would you use bis, tri, tetrakis? And are we using it instead of di, tri, tetra, etc?
by melissa_dis4K
Wed Dec 05, 2018 12:37 pm
Forum: Naming
Topic: Difference between chloro and chlorido
Replies: 1
Views: 9

Difference between chloro and chlorido

Are chloro and chlorido the same?
by melissa_dis4K
Wed Dec 05, 2018 11:56 am
Forum: Naming
Topic: Oxidation number
Replies: 2
Views: 30

Oxidation number

When finding the oxidation number do I need to do the Lewis structure to find the charge of Cl, for example in [Fe Cl(OH2)5]^+ Or how can I find the charge of chloride to be able to find the oxidation number of the central atom? Thank you!
by melissa_dis4K
Wed Nov 28, 2018 11:16 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarity of ClF3
Replies: 1
Views: 18

polarity of ClF3

Is it safe to assume that because all the atoms besides the central atom of ClF3 is polar because they are the same element or should the charges always be taken into consideration when determining polarity?
by melissa_dis4K
Wed Nov 28, 2018 10:35 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizing power and polarizability
Replies: 4
Views: 55

Polarizing power and polarizability

Can someone please explain polarizing power and polarizability in an easy way for me to understand? I don't understand the definition. Thank you
by melissa_dis4K
Wed Nov 28, 2018 10:23 pm
Forum: Electronegativity
Topic: Ionic character
Replies: 2
Views: 28

Ionic character

Just to clarify, when looking at the greater ionic character, the difference between the electronegativity of the two atoms, do the number of atoms, the subscripts make a difference? For example, comparing the molecules H (subscript 2)S and HCl. I know that HCl has the greater ionic character, but d...
by melissa_dis4K
Wed Nov 28, 2018 10:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 5
Views: 38

Re: Polarity

Nvm to that^ that makes sense thanks!
by melissa_dis4K
Wed Nov 28, 2018 10:12 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 5
Views: 38

Re: Polarity

Thank you! Regarding the dipole moment is there only one from the N to the O without the double bond? And if so do the formal charges "give it" its partial charge. I'm basing this idea off from the worksheet posted for "ch3; Chemical Bonds"
by melissa_dis4K
Wed Nov 28, 2018 10:08 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: How to identify polarity
Replies: 2
Views: 29

How to identify polarity

I'm having a lot of trouble understanding polarity, can someone please help and explain how it is that we identify polar molecules. I know that polar is the unequal sharing of electrons and that if the dipole moments cancel it is nonpolar. However, I am just having trouble applying it to the actual ...
by melissa_dis4K
Wed Nov 28, 2018 10:02 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polarity
Replies: 5
Views: 38

Polarity

Can someone please explain why NO2 is polar? Is it just because they are the same atoms and have an unequal sharing of electrons? Do the dipole moments not cancel out? If not, is this because the molecule is bent due to the unpaired lone electron on the N atom? Thanks
by melissa_dis4K
Thu Nov 15, 2018 12:50 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Will we have to calculate bond angles?
Replies: 8
Views: 71

Re: Will we have to calculate bond angles?

I believe that we should know which angles are associated with the types of shapes. I'm not sure that we will necessarily be calculating them, I think that knowing them will be very helpful.
by melissa_dis4K
Thu Nov 15, 2018 12:47 am
Forum: Determining Molecular Shape (VSEPR)
Topic: See-Saw Shape
Replies: 3
Views: 48

Re: See-Saw Shape

Hello! I believe that see saw shape is one in which the central atom has 5 regions of electron density, 4 being bonds between the atoms and the 5th being the lone pair. For example, in the Lewis structure for TeCl(subscript 4), Te is the central atom and when all formal charges equal 0, Te has five ...
by melissa_dis4K
Thu Nov 15, 2018 12:34 am
Forum: Octet Exceptions
Topic: d orbital period 3
Replies: 2
Views: 65

d orbital period 3

I understand that Sulfur can have an expanded orbital, thus it has a d orbital. But if you do the electron configuration for Sulfur it is [Ne]3s^2 3p^4. I don't understand how it has a d orbital. Can someone please explain?
by melissa_dis4K
Mon Nov 05, 2018 10:57 am
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 4202

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

does anyone know how to solve 8b? i am having trouble with it. First convert the work function from kJ/mol into J and convert lambda into meters. Then using E(photon)- work function =kinetic energy, we will be solving for E(photon). But first we need to know the kinetic energy to do so use Ek=1/2 M...
by melissa_dis4K
Sun Nov 04, 2018 9:10 pm
Forum: Properties of Electrons
Topic: Electron Configuration
Replies: 7
Views: 59

Electron Configuration

For the electron configuration of Pd I get [Kr]4d^8 5s^2 but it is [Kr] 4d^10. My question is do we change it to [Kr] 4d^10 because we should fill in the entire d orbital before continuing to the 5s orbital? Is this always?
by melissa_dis4K
Sun Nov 04, 2018 8:33 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 4202

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

Could someone explain 13c to me? -13c is a Heisenberg Uncertainty Principle problem. The equation for this problem is ΔPΔX=>h/4pi. For this equation we need the mass, the velocity(these two values multipled together are ΔP), and we need ultimately to find ΔX. -We are given the mass which is 2.8 gra...
by melissa_dis4K
Sun Nov 04, 2018 8:00 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron Configuration
Replies: 4
Views: 39

Re: Electron Configuration

Thank you! So does this only happen for ions and elements like Cu and Cr?
by melissa_dis4K
Sun Nov 04, 2018 7:36 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 4202

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

For number 11, part b why would delta E be a negative value? If the problem is asking for the change in energy from n = 6 to n = 4, and the formula is E = -hR(1/n1^2 - 1/n2^2), the energy released from n = 6 to n = 4 equals 7.5689 x 10^-20 J. So, why is the answer negative? Remember that the change...
by melissa_dis4K
Sun Nov 04, 2018 7:01 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Electron Configuration
Replies: 4
Views: 39

Electron Configuration

The abbreviated electron confuration of Ni3+ is [Ar]3d^7. Just to clarify even though while I did this I got [Ar]3d^5 4s^2, the electrons in the 4s orbital will move to the 3d orbital to fill that up first. Is this always true or an exception. I.e. will electrons always fill in the previous levels f...
by melissa_dis4K
Sun Nov 04, 2018 6:47 pm
Forum: Administrative Questions and Class Announcements
Topic: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]
Replies: 121
Views: 4202

Re: MIDTERM PRACTICE - Garlic Bread Review Session [ENDORSED]

For 8B I understand that we need to use E(photon) - work function = kinetic energy. We are given the wavelength and work function. However, I don't know where to use the wavelength since E(photon)=h*frequency and we have the given work function and Kinetic energy= 1/2 Mass* Velocity(unknown). Can so...
by melissa_dis4K
Sat Nov 03, 2018 1:49 pm
Forum: Properties of Electrons
Topic: Excitation of an atom
Replies: 1
Views: 36

Excitation of an atom

This may be very simple, but I am trying to understand why it is that when an atom is excited it gains energy? Is there an easier visual way for me to understand this?
by melissa_dis4K
Sat Nov 03, 2018 12:13 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Module Question 20
Replies: 4
Views: 119

Re: Module Question 20

To calculate the uncertainty in kinetic energy you need to use the uncertainty of velocity from the previous problem: delta v=3.3*10^10 m/s. Then use the formula for kinetic energy= 1/2 Mass * Velocity^2. Plug in the mass of an electron (given) 9.11*10^-31 and the velocity from the previous problem ...
by melissa_dis4K
Fri Nov 02, 2018 12:05 am
Forum: Electronegativity
Topic: Electron Configuration
Replies: 2
Views: 22

Electron Configuration

When finding the electron configuration for Cerium, it is [Xe] 4f^1 5d^1 6s^2, I understand the 5d^1 and 6s^2, however I am confused on where and how we get 4f^1. I'm just confused on how to find it for the f-block. I know that for the d-block we have to take the period and subtract one is there som...
by melissa_dis4K
Wed Oct 24, 2018 7:37 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Homework 2.39
Replies: 1
Views: 23

Homework 2.39

This is from the sixth edition.. I'm having trouble understanding the difference between ground state and excited state can someone pls explain? Thank you!
by melissa_dis4K
Tue Oct 23, 2018 12:51 pm
Forum: Photoelectric Effect
Topic: Module question 30 c
Replies: 4
Views: 107

Re: Module question 30 c

I realized my answer is wrong can someone explain what I did wrong? Thanks!
by melissa_dis4K
Tue Oct 23, 2018 12:32 pm
Forum: Photoelectric Effect
Topic: 34B Photoelectric effect module
Replies: 2
Views: 92

34B Photoelectric effect module

34. B. If molybdenum is irradiated with 194 nm light, what is the maximum possible kinetic energy of the emitted electrons? For the previous question part a I got E=7.22 x 10^-19. However, I am not sure how to solve this problem. I think I should use Kinetic Energy=1/2Me*Ve^2. But, I don't know how ...
by melissa_dis4K
Tue Oct 23, 2018 12:05 pm
Forum: Photoelectric Effect
Topic: Module question 30 c
Replies: 4
Views: 107

Re: Module question 30 c

Thank you, it did help! I was overthinking the equations. But, now I got 150.6 J for question 29b when I added the work function plus my answer from 28a. I then used frequency=E/h and got 2.27 x 10^35. However, the answer seems to be to the power of 38. Do you know why I get the wrong power sometimes?
by melissa_dis4K
Tue Oct 23, 2018 11:14 am
Forum: Properties of Light
Topic: Power calculations
Replies: 6
Views: 136

Power calculations

When I am calculating sometimes I get the wrong power on my calculator and was wondering if anyone knew why this is? I do make sure I input everything correctly and that I use parentheses.
by melissa_dis4K
Sun Oct 21, 2018 10:48 pm
Forum: Photoelectric Effect
Topic: Module question 30 c
Replies: 4
Views: 107

Module question 30 c

The question asks "Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 10^5 m.s-1. The work function for sodium is 150.6 kJ.mol-1. What is the frequency of the incident light on the sodium metal surface?" I began by doing E=h*v(frequency). However, I don't ...
by melissa_dis4K
Sun Oct 21, 2018 10:36 pm
Forum: Photoelectric Effect
Topic: module question 28 a
Replies: 1
Views: 23

module question 28 a

For this question, "Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 10^5 m.s-1. The work function for sodium is 150.6 kJ.mol-1. What is the kinetic energy of the ejected electron?" I know that E(photon)-E(energy remove e-)=Kinetic energy of the electron...
by melissa_dis4K
Sun Oct 21, 2018 10:17 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Module Question 27
Replies: 2
Views: 28

Photoelectric Effect Module Question 27

For question 27 it asks "Calculate the energy per photon of ultraviolet radiation of frequency 3.00 x 1015 Hz." What I did was, using E=h*frequency(v) and c=lambda*frequency(v) I solved for E by rearranging the equations to give E=hc/lambda =(6.626*10^-34 Js)(3.00 x 10^8 ms^-1)/3.00 x 10^1...
by melissa_dis4K
Thu Oct 11, 2018 12:19 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Molar mass
Replies: 3
Views: 117

Molar mass

How do you know when to multiply the molar mass by the coefficients? Or we do always?
by melissa_dis4K
Wed Oct 10, 2018 7:03 pm
Forum: Limiting Reactant Calculations
Topic: Module Question #18 Help
Replies: 1
Views: 76

Re: Module Question #18 Help

I have the exact same calculations you have... From the 4:5 ratio based on the balanced equation, for the calculated 1.26 mol NH3, 1.58 mol O2 are required. However, from the calculation it is only 1.33 mol of O2, so yes the product produced will depend on the limiting reactant which in this case is...
by melissa_dis4K
Tue Oct 09, 2018 11:51 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E15 homework problem
Replies: 2
Views: 89

Re: E15 homework problem

Thanks, this helped!
by melissa_dis4K
Tue Oct 09, 2018 10:47 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E15 homework problem
Replies: 2
Views: 89

E15 homework problem

On question E15, the question says: "The molar mass of the metal hydroxide M(OH)2 is 74.10 gmol1. What is the molar mass of the sulfide of this metal?" I got confused that it said "sulfide" does anyone know what that refers to in the formula?
by melissa_dis4K
Thu Oct 04, 2018 3:08 pm
Forum: Molarity, Solutions, Dilutions
Topic: Molarity and Dilution of a Solution Post Module Assessment Question 25
Replies: 5
Views: 74

Re: Molarity and Dilution of a Solution Post Module Assessment Question 25

Can someone please explain why the initial volume is 0.02 L? I thought it was 0.15 L? Thank you!
by melissa_dis4K
Tue Oct 02, 2018 4:45 pm
Forum: Significant Figures
Topic: Significant figures for molar mass
Replies: 7
Views: 146

Significant figures for molar mass

When doing the process of finding the moles of each element (having to divide the mass of the element by the atomic mass/mole of an element), how do we determine how many significant figures to use? For example, molar mass of Carbon, do I use 12.01 g/mol or 12.011 g/mol? How do you differentiate whe...
by melissa_dis4K
Tue Oct 02, 2018 4:28 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Mass calculation
Replies: 2
Views: 48

Mass calculation

On the video module under Empirical and Molecular formulas, the example of finding the molecular formula for vitamin C, the molar mass given for the compound is 176.14gmol^-1. Then I take the empirical formula C3H4O3 and multiply it by 2.000 to get the molecular formula C6H8O6. What I am confused on...

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