## Search found 61 matches

Sat Mar 16, 2019 9:34 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram
Replies: 4
Views: 119

### Re: Cell Diagram

In half reactions that do not already have a solid, then yes Pt will be used. There are instances where Hg can also be used as the inert electrode.
Sat Mar 16, 2019 9:09 am
Forum: First Order Reactions
Topic: 6th edition 15.29
Replies: 2
Views: 258

### Re: 6th edition 15.29

When you solve for t using the first order equation it should be t = -(lnA-lnA0)/k. In the solutions manual, they multiply the negative in, so that it becomes t = (lnA0 - lnA)/k, so that it is ln0.015/0.05.
Sat Mar 16, 2019 9:03 am
Forum: General Rate Laws
Topic: approximation
Replies: 2
Views: 99

### Re: approximation

If you are talking about when you find the order of the rate laws, then yes you can approximate, since he mentioned that we should not have fraction orders.
Sun Mar 10, 2019 11:35 pm
Forum: General Rate Laws
Topic: Integrated Rate Laws
Replies: 1
Views: 50

### Re: Integrated Rate Laws

Looking at the constants and equations sheet from his site, most of the integrated rate laws are there. However, the first order exponential decay integrated law (derived from the first order integrated law) is not on there and we had hw problems on this, so I am guessing we would need to know this ...
Sun Mar 10, 2019 11:30 pm
Forum: First Order Reactions
Topic: 15.23 c) Determining rate constant
Replies: 2
Views: 129

### 15.23 c) Determining rate constant

2 A-->B + C, given that [A]0 = 0.153 M and that after 115 s the concentration of B rises to 0.034M.

I am confused on how the solution manual explains how to find the rate constant in this question!
Sun Mar 10, 2019 10:16 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.13 b) Doubling H2 concentration
Replies: 1
Views: 98

### 15.13 b) Doubling H2 concentration

Why for part b of this question is the factor 2 if the concentration of H2 is doubled? When 0.52 g of H2 and 0.19 g of I2 are confined to a 750.-mL reaction vessel and heated to 700. K, they react by a second-order process (fi rst order in each reactant), with k " 0.063 L/mol.s in the rate law ...
Wed Feb 27, 2019 12:18 am
Forum: Administrative Questions and Class Announcements
Topic: Test 2 6th Edition Questions
Replies: 1
Views: 133

### Re: Test 2 6th Edition Questions

For chapter 14, I believe we go up to question either 33 or 35!
Wed Feb 27, 2019 12:14 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.15(c) Cell Diagram
Replies: 1
Views: 78

### 14.15(c) Cell Diagram

For this question, how did we know to use Ni(s) as the inert metallic component, instead of something like Pt(s)?
Cd(s) + 2 Ni(OH)3(s) --> Cd(OH)2(s) + 2 Ni(OH)2(s), the reaction in the nickel–cadmium cell
Tue Feb 26, 2019 11:30 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams in 14.15 and 14.17 6th Ed
Replies: 4
Views: 185

### Re: Cell Diagrams in 14.15 and 14.17 6th Ed

Kobe_Wright wrote:When two aqueous solutions are in the same cell they're split with a comma while if they're other phases they're separated with a line.

Right, but Ni(OH)3(s) and Ni(OH)2(s) are in the same phase still and is still separated by a line?
Tue Feb 26, 2019 10:43 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams in 14.15 and 14.17 6th Ed
Replies: 4
Views: 185

### Cell Diagrams in 14.15 and 14.17 6th Ed

For these answers, I am confused on why for 15 the Ni(OH)3(s) and Ni(OH)2(s) is only separated by a line, whereas in 17 MnO4-(aq) and Mn2+(aq) has a comma separating them?
Sun Feb 24, 2019 9:33 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 3
Views: 114

### Re: Salt Bridge

A salt bridge allows for ion transfer, when there is a charge buildup from the electrons transferring between the beakers, and it ensures that the two solutions stay neutral.
Sun Feb 24, 2019 7:29 pm
Forum: Student Social/Study Group
Topic: Final
Replies: 24
Views: 1026

### Re: Final

Yes, but he has review sessions every week to prepare leading up to the final.
Sun Feb 24, 2019 7:23 pm
Forum: Student Social/Study Group
Topic: Test #2
Replies: 7
Views: 309

### Re: Test #2

Specifically, Test 2 covers all topics on Gibbs free energy and electrochemistry (not including the Nernst equation). It really is up to you to see where you struggle more on in the homework and this should reflect what you need to focus more on for the test.
Tue Feb 12, 2019 11:13 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Quiz 1 #5
Replies: 7
Views: 458

### Re: Quiz 1 #5

I think each discussion had similar questions, so I am not sure if we have the exact same question, but I can go over the steps. What is given is the reaction and since one of the products is OH-, you know that sodium ascorbate (or whichever it says on your test) is a base. Because what they give is...
Tue Feb 12, 2019 11:00 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Equations
Replies: 5
Views: 460

### Re: Equations

I don't think we will have to necessarily to memorize any equation, since anything we will need will be given to us on the constants and formula sheets, but maybe memorize the units for something like entropy or enthalpy to help see what equation to use.
Tue Feb 12, 2019 10:55 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.45 Sixth Edition
Replies: 1
Views: 92

### 9.45 Sixth Edition

For this question, they ask to solve for both delta s surroundings and delta s systems, and I understand how to solve the question, but in the solution manual for both delta s surroundings and delta s systems they use delta H system as the q. Should it not switch between delta H system and delta H s...
Sun Feb 10, 2019 4:56 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.15b 6th edition
Replies: 1
Views: 93

### Re: 9.15b 6th edition

I solved it by first converting the 50 grams of ethanol to moles and then multiplying it to 43.5 kJ/mol to get delta H of vaporization. Then by dividing delta H by the vaporizing temperature to get delta S.
Thu Feb 07, 2019 10:47 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond enthalpies
Replies: 3
Views: 175

### Re: Bond enthalpies

Eruchi Okpara 2E wrote:Are we expected to automatically know all the lewis structures/resonance structures in order to solve bond enthalpy problems?

I believe so since this was covered in Chem 14a and they wouldn't give the lewis structures to us on the test either.
Thu Feb 07, 2019 10:44 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: 8.53 Bomb Calorimeter 6th Ed
Replies: 1
Views: 103

### 8.53 Bomb Calorimeter 6th Ed

In question 53, the solution manual mentions that because it is in a bomb calorimeter you know that the volume is fixed. Can someone explain to me why? I also had the question of why the q being calculated is negative? The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carb...
Fri Feb 01, 2019 12:03 am
Forum: Calculating Work of Expansion
Topic: Isolated System
Replies: 5
Views: 2545

### Re: Isolated System

You are right in the sense that in an isolated system nothing is exchanged, therefore no heat should be exchanged either, so you should not consider the heat in the surroundings.
Thu Jan 31, 2019 11:40 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.57 6th Edition Units
Replies: 1
Views: 51

### 8.57 6th Edition Units

I noticed that in this question for the given values the units were kJ/mol (ex: -1300 kJ/mol), but in the solution manual the delta H were all in kJ? Which units do you use when calculating then?
Thu Jan 31, 2019 11:35 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.65 6th Edition
Replies: 2
Views: 88

### 8.65 6th Edition

I understand that we use the formula of products minus reactants, and I ended up with the product (N2O5) but why is the O2 not in the equation for the reactants (2NO and 3/2O2)? Calculate the standard enthalpy of formation of dinitrogen pentoxide from the following data, 2 NO + O2 --> 2 NO2 \bigtria...
Sun Jan 27, 2019 8:02 pm
Forum: Phase Changes & Related Calculations
Topic: Memorizing unit conversions?
Replies: 3
Views: 126

### Re: Memorizing unit conversions?

I believe they should be all provided on the constants and equations sheet given.
Sun Jan 27, 2019 8:00 pm
Forum: Phase Changes & Related Calculations
Topic: State Properties
Replies: 5
Views: 167

### State Properties

For lecture on Wednesday, I think he mentioned that enthalpy, pressure, volume and temperature are state properties but why are work and heat not considered as state properties?
Thu Jan 24, 2019 5:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.57 6th Edition
Replies: 2
Views: 101

### 11.57 6th Edition

A reaction mixture consisting of 2.00 mol CO and 3.00 mol H2 is placed in a 10.0-L reaction vessel and heated to 1200. K. At equilibrium, 0.478 mol CH4 was present in the system. Determine the value of Kc for the reaction In the solutions manual, they used moles in their ICE table, can we just conve...
Sun Jan 20, 2019 11:30 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Number 69 Ch.12
Replies: 1
Views: 60

### Re: Number 69 Ch.12

Did you look at table 12.8 in the textbook? I think the Ka values are the same number in both the textbook and the solution manual (1.4 x 10^-5), is that what you are asking?
Sun Jan 20, 2019 10:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 12.69 (b) 6th Edition
Replies: 1
Views: 108

### 12.69 (b) 6th Edition

Calculate the pH of each of the following solutions: (b) 0.055 m AlCl3(aq)

In the solution manual they used Al(H20)6 in place of Cl3 and I am confused on this set up, if someone could clarify this thank you!
Sun Jan 20, 2019 8:47 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Question 12.55 (Sixth Edition)
Replies: 1
Views: 97

### Re: Question 12.55 (Sixth Edition)

You would first need to do an ICE table to find x, which will tell you your CH3CO2 concentration (for example in part a). After finding this, you should divide it by your initial concentration of CH3COOH (0.20 M in part a) to get your percentage deprotonation. For what percentage deprotonation is, I...
Sun Jan 13, 2019 7:52 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: K vs Q
Replies: 4
Views: 160

### Re: K vs Q

For the reaction quotient, Q you are able to measure to the concentration of the reaction at any given time (could be not at equilibrium). In ways they are similar, they are pretty much calculated in the same way with products divided by reactants (including the coefficients as well). Q could also b...
Sat Jan 12, 2019 6:20 pm
Forum: Ideal Gases
Topic: bar or atm
Replies: 8
Views: 273

### Re: bar or atm

I don't think we will need to know since there are so close anyways and I think whatever the question uses the answer will be in those units.
Sat Jan 12, 2019 4:46 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 11.39 6th Ed Multiplying K constants
Replies: 3
Views: 99

### 11.39 6th Ed Multiplying K constants

Use the information in Table 11.2 to determine the value of K at 300 K for the reaction 2 BrCl(g) + H2(g) --> Br2(g) + 2 HCl(g).

I understand that this reaction is separated into two different reactions, but I'm not sure why we multiply the two k equilibrium constants.

Thank you!
Fri Dec 07, 2018 9:40 am
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Strong Acids
Replies: 5
Views: 262

### Re: Strong Acids

I think we are expected to know the difference between strong and weak acids, but yes most of the calculations will be with strong acids. I hope this answered your question!
Thu Dec 06, 2018 11:11 pm
Forum: Bronsted Acids & Bases
Topic: 6th Ed 12.65d Neutral pH
Replies: 1
Views: 134

### 6th Ed 12.65d Neutral pH

Determine whether an aqueous solution of each of the following salts has a pH equal to, greater than, or less than 7. If pH & 7 or pH ' 7, write a chemical equation to justify your answer. (d) KBr e) AlCl3; (f) Cu(NO3)2. Why is part d considered neutral? And for parts e and f why is the Cl and N...
Thu Dec 06, 2018 9:23 am
Forum: Lewis Acids & Bases
Topic: 12.25 6th Edition Initial Molarity
Replies: 1
Views: 63

### 12.25 6th Edition Initial Molarity

Calculate the initial molarity of Ba(OH)2 and the molarities of Ba2+, OH-, and H3O+ in an aqueous solution that contains 0.43 g of Ba(OH)2 in 0.100 L of solution

In the solutions manual, I am confused on why they multiply the molarity [Ba(OH)]2 by 2?
Sun Dec 02, 2018 9:01 pm
Forum: Biological Examples
Topic: Biological Importance of Coordination Compounds
Replies: 3
Views: 155

### Re: Biological Importance of Coordination Compounds

I don't think we need to know much, but probably we only be tested on the examples he mentioned in class, like myoglobin.
Wed Nov 28, 2018 5:05 pm
Forum: Hybridization
Topic: 4.43 Increasing s-character of hybrids
Replies: 2
Views: 105

### 4.43 Increasing s-character of hybrids

Why is it that increasing s-character also increases bond angle?

Noting that the bond angle of an sp3 hybridized atom is 109.5 and that of an sp2 hybridized atom is 120#, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased?
Mon Nov 26, 2018 9:15 am
Forum: Hybridization
Topic: Just Kind of Confused
Replies: 13
Views: 376

### Re: Just Kind of Confused

the order doesn't matter! But in class he said he prefers sp, sp2, sp3, dsp3, and d2sp3.
Sun Nov 25, 2018 9:16 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Test 3
Replies: 38
Views: 1160

### Re: Test 3

I thought he said that we will not need to know bond angle. That we will be asked to draw the Lewis Structure and then name the shape. I think he doesn't expect us to know the exact bond angle (like 107)' but we should know and write it as less than 109.5' for something like the trigonal pyramid sh...
Sun Nov 25, 2018 9:10 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: T-Shaped
Replies: 5
Views: 248

### Re: T-Shaped

The t-shaped molecule is made up of 3 atoms. One goes straight up, one goes straight down, and one is perpendicular to the two. So the bond angles between the perpendicular atom and the other two atoms are 90 degrees. The bond angle between the atom going straight down and straight up is 180 degree...
Sat Nov 24, 2018 9:40 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: 4.13 6th Edition: VSEPR formula for I3-
Replies: 1
Views: 31

### 4.13 6th Edition: VSEPR formula for I3-

Write the Lewis structure, VSEPR formula, molecular shape, and bond angles for each of the following species: ${I_{3}}^{-}$

Why is it that the molecular shape of ${I_{3}}^{-}$ is linear and not bent?
Mon Nov 19, 2018 5:09 pm
Forum: Hybridization
Topic: Ethene Hybridization
Replies: 4
Views: 131

### Ethene Hybridization

In today's lecture, Ethene was one of the hybridization examples, why is it that we needed the unhybridized 2p orbital along with the 2sp^2?
Mon Nov 19, 2018 4:50 pm
Forum: Administrative Questions and Class Announcements
Topic: Workshops
Replies: 5
Views: 328

### Re: Workshops

I think there still will be one tomorrow from 6-8 at Covel Commons!
Mon Nov 19, 2018 4:41 pm
Forum: Hybridization
Topic: Hybridization
Replies: 3
Views: 130

### Re: Hybridization

Hybridization is the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. Like Lavelle said in class, its easier to start by figurin...
Sun Nov 11, 2018 11:06 pm
Forum: Bond Lengths & Energies
Topic: High Boiling Points and Bond Strengths [ENDORSED]
Replies: 4
Views: 234

### High Boiling Points and Bond Strengths[ENDORSED]

I just wanted to make sure I was understanding this correctly, in class I believed he used an example of pentane and 2,2-dimethylpropane and that pentane was rod-shaped. It is because of the higher boiling point (rod-shaped) that the bonds are harder to break versus the spherical shape?
Sun Nov 11, 2018 10:56 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: 6.1 Sixth Edition Intermolecular Forces
Replies: 2
Views: 1073

### 6.1 Sixth Edition Intermolecular Forces

In this question, why is it that NH2OH has london forces, dipole-dipole, hydrogen bonding, but CBr4 only has London forces listed?

Identify the kinds of intermolecular forces that might arise between molecules of each of the following substances: (a) NH2OH; (b) CBr4;
Sun Nov 11, 2018 5:38 pm
Forum: Bond Lengths & Energies
Topic: 3.121 6th ed
Replies: 1
Views: 94

### Re: 3.121 6th ed

To begin this type of problem, try counting the total number of valence electrons for each compound, then apply the octet rule, and then check formal chargers to make sure that this form is the most stable. So for part (a) methanethiol CH3SH will have 14 valence electrons in total. Carbon will then ...
Sun Nov 04, 2018 11:18 pm
Forum: Trends in The Periodic Table
Topic: Higher Electron Affinity Nitrogen or Carbon
Replies: 4
Views: 471

### Higher Electron Affinity Nitrogen or Carbon

Hi! I was just wondering which element has a higher electron affinity nitrogen or carbon and why? I think this is one of the exceptions and I am not sure.
Sun Nov 04, 2018 6:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 2.43 Tungsten
Replies: 1
Views: 108

### 2.43 Tungsten

Hi could someone explain to me why the electron configuration for Tungsten is
[Xe]4f145d46s2 instead using the same rule (exception) for chromium?
Sun Nov 04, 2018 2:17 pm
Forum: Trends in The Periodic Table
Topic: 2.37 (c)
Replies: 1
Views: 46

### 2.37 (c)

Hi! I am bit confused on why the statement below is false, if someone could clarify this for me thank you!

(c) Electrons having l =2 are better at shielding than electrons having l = 1.
Sun Oct 28, 2018 10:26 pm
Forum: Trends in The Periodic Table
Topic: Lewis Structures
Replies: 7
Views: 339

### Re: Lewis Structures

The dots can go on any four sides, but keep in mind that two dots next to each other means that those two electrons are paired. If the 4 electrons that you're drawing aren't paired, the structure would have one dot on each of the 4 sides. I have a similar question from this: A line drawn between tw...
Sun Oct 28, 2018 10:18 pm
Forum: Trends in The Periodic Table
Topic: s-block and p-block reactivity?
Replies: 6
Views: 299

### s-block and p-block reactivity?

I believe it is question 2.75 in the sixth edition where it is asking about whether the s-block or the p-block is more reactive. I know that elements in the s-block have lower ionization energies, but does this quality make it more reactive than p-block?
Thu Oct 25, 2018 7:44 pm
Forum: Quantum Numbers and The H-Atom
Topic: 2.29 Sixth Ed. (c)
Replies: 1
Views: 66

### 2.29 Sixth Ed. (c)

The solutions manual states that this has eight electrons for part c, I am just confused on how that was determined using only n?

How many electrons can have the following quantum numbers in an atom:
c) n =2
Sat Oct 20, 2018 11:54 pm
Forum: Einstein Equation
Topic: Using Joules
Replies: 2
Views: 212

### Using Joules

When do you know to use the equivalent of Joules units (kgm^2s^-2)? Is it so that we can cancel in dimensional analysis?
Sat Oct 20, 2018 11:46 pm
Forum: Properties of Light
Topic: Visible Light
Replies: 5
Views: 151

### Re: Visible Light

In the book and the lecture I think he mentioned that it is from 420-700 nm.
Sat Oct 20, 2018 11:27 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Prob 1.15 6th Ed.
Replies: 2
Views: 108

### Re: Prob 1.15 6th Ed.

How would you solve this using the equation Professor Lavelle showed us in class?
Fri Oct 12, 2018 1:18 am
Forum: Balancing Chemical Reactions
Topic: Seventh Edition- H21 [ENDORSED]
Replies: 3
Views: 340

### Re: Seventh Edition- H21[ENDORSED]

I also struggled with this one!! But, to make it less confusing: after I balanced 2C10H15N, so that nitrogen would be balanced, I made sure to match everything else to this as well. You don’t want to keep adding to this as it is harder to manipulate whereas oxygen is easier to work with.
Thu Oct 11, 2018 11:57 pm
Forum: Balancing Chemical Reactions
Topic: L.5 Part B Sixth Edition [ENDORSED]
Replies: 5
Views: 256

### Re: L.5 Part B Sixth Edition[ENDORSED]

Here is my work for b, maybe your ratios were incorrect? Hope this helps!
Thu Oct 11, 2018 11:28 pm
Forum: Limiting Reactant Calculations
Topic: HW1 M19
Replies: 3
Views: 325

### Re: HW1 M19

Do we have to first convert the grams of each compound into moles and then find the mass of the individual elements from there? Yes, but remember to also look at your stoichiometric coefficients for the ratios to compare to and then find the mass of the individual elements. To find the mass of O su...
Fri Oct 05, 2018 12:18 am
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E5 (b)
Replies: 1
Views: 103

### E5 (b)

Hello! I am confused on how to set up part b of this problem and how it would end in time units? The approximate population of Earth is 7.0 billion people. How many moles of people inhabit Earth? (b) If all people were pea pickers, how long would it take for the entire population of Earth to pick 1 ...
Thu Oct 04, 2018 11:39 pm
Forum: Limiting Reactant Calculations
Topic: Comparing Calculated Moles step M7(b)
Replies: 2
Views: 259

### Comparing Calculated Moles step M7(b)

Solid boron can be extracted from solid boron oxide by reaction with magnesium metal at a high temperature. A second product is solid magnesium oxide. (a) Write a balanced equation for the reaction. (b) What mass of boron can be produced when 125 kg of boron oxide is heated with 125 kg of magnesium?...
Tue Oct 02, 2018 10:40 pm
Forum: Empirical & Molecular Formulas
Topic: Using the Mass Spectrum in F17(b)
Replies: 2
Views: 366

### Using the Mass Spectrum in F17(b)

In this question, I knew that I needed the mass spectrum to calculate the molecular formula, but why do we divide the molar mass of 907g/mol by the empirical formula molar mass? F17 Osmium forms a molecular compound with mass percentage composition 15.89% C, 21.18% O, and 62.93% Os b) From the mass ...