CHEMISTRY COMMUNITY

Alexandra_Ivanova_1A

Minu Reddy wrote:Hi Everyone,
I was wondering if we need to know how to draw a boat conformation?

Thank you

Not sure about what the other replier said, but Professor Lavelle said we only need to know how to draw a chair conformation on the test. You should be able to identify the other conformations though.

Alexandra_Ivanova_1A

I'd post more chemistry jokes on here, but I feel like the sheer amount of content on here might Barium.

Alexandra_Ivanova_1A

Alexandra_Ivanova_1A

Are we expected to know how to balance reactions in both acidic and basic solutions? Will it be specified in the problem which it is? What if the reaction is occuring in water?

Alexandra_Ivanova_1A

Do we only use the reversible work equation when it is explicitly stated the reaction is reversible? When do we know a reaction is reversible? Is isothermal synonymous with reversible (i.e, do we use the reversible work equation when isothermal is stated in the question?)

Alexandra_Ivanova_1A

I've noticed in the textbook/course reader when balancing equations to calculate things like enthalpy and entropy sometimes we balance the equations with integers, and other times we will have values that are fractions. When do we know when it is necessary to use integers and when not to, since this...

Alexandra_Ivanova_1A

In the Solutions Manual, it says that since a bomb calorimeter is used, the volume is fixed, and therefore w=0. Is this the case for all closed systems?

Alexandra_Ivanova_1A

Since no pressure or volume is indicated, we use PV=nRT to find PV and then find the change in internal energy for the rxn by using the equation:
(delta U)=(delta H)-(PV). Since the reaction is at standard conditions, I think we assume the pressure is constant.

Alexandra_Ivanova_1A

I understand that the standard enthalpy of formation an element in its standard state is zero, however I'm confused as to the reactions used to signify them: O 2 --> O 2 Br 2 --> Br 2 ...etc. What exactly do these reactions mean? What is the purpose of a reaction where the products and reactants are...

Alexandra_Ivanova_1A

1. The solid sodium acetate will dissociate into separate sodium and separate acetate, so you will be adding additional acetate to the solution and the concentration of H3O+ will in turn decrease. 2. Percentage deprotonation is the conjugate base over its acid. Keeping that in mind. when adding hydr...

Alexandra_Ivanova_1A

I think it has more to do with what is actually reacting. In the example you are using, we are looking at NH 4 Cl. This is a salt that contains an acid within it (NH 4 ). The acid is what is reacting with water, not the anion (Cl - ). Since Cl - isn't reacting, it doesn't affect the pH. This is furt...

Alexandra_Ivanova_1A

I know that hydroxides of the metals of Group 3 (and higher) generally tend to have amphoteric properties and are slightly basic, so I suppose it depends on the compound itself. "In general, these compounds tend to be more basic than acidic; thus, the oxides and hydroxides of aluminum, iron, an...

Alexandra_Ivanova_1A

You're referring to the table on page 117 of the course reader, yes? If so, the asterisk means that the ligand is polydentate (chelate).

Alexandra_Ivanova_1A

On page 116 of the Course Reader, the notes cover cis-diamminedichloroplatinum(II) as well as trans-diamminedichloriplatinum(II). Aside from what they are able to/are more likely bond to, what are the differences in the properties of a cis and trans version of a molecule, and how would each form? Is...

Alexandra_Ivanova_1A

A trigonal pyramidal shape occurs when an atom has four areas of electron density-- a lone pair of electrons, and three bonds. In the case of ClO₂⁺, it does have four regions of electron density, but it has two lone pairs and two bonds, so it follows a bent structure instead.

Alexandra_Ivanova_1A

Where can I find out how to do the valence electron configuration notation needed for problems like 6 and 7 in the Quiz 2 Preparation, Fall 2014 problem set? Will it be covered in the upcoming quiz if it hasn't been explicitly discussed in class?

Alexandra_Ivanova_1A

You're right-- Nobel gases (Group 18 elements) contain a full octet, so they don't usually (or at least, do not easily) form bonds with other elements. That being said, it is possible for them to bond, though that bond is often very weak. Typically, elements n=3 and above don't follow the octet rule...

Alexandra_Ivanova_1A

Thank you so much, that video was really helpful. I find that this Khan Academy series is helpful too: https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/electron-configurations-jay-sal/v/orbitals

Alexandra_Ivanova_1A

I believe there is an error in the solutions manual. On Lavelle's website, the "Solutions Manual Errors" state: 2.93 In the picture, it shows A (smaller atom) + B (larger atom) --> C (larger ion) + D (smaller ion) The solution manual says that A=Na and B=Cl, and it references Figure 2.20 w...

Alexandra_Ivanova_1A

Yes, a negative energy means that light is being emitted, while a positive one means light is being absorbed.

Alexandra_Ivanova_1A

From looking at the solutions in the textbook solutions manual and workbook, it constantly wants us to round off to the proper number of sig figs at each step of the problem. If you do that, it's easier to keep track of sig figs from the beginning because you just end up with the smallest number of...

Alexandra_Ivanova_1A

For 1.33C you use the equation E potential = E threshold + E kinetic . In part B, you find the threshold energy using the given frequency (2.50 x 10 16 Hz) and the equation E = hv. Page 43 of the Course Reader goes over this a bit, but essentially, the equation for kinetic energy is (0.5)*(mass of e...

Alexandra_Ivanova_1A

How much wiggle room do we have in terms of rounding accuracy during the tests, quizzes, etc? I know that general rounding and significant figure rules stated in the beginning of the Course Reader apply, but it seems like using certain constants or rounding off constants can give a bit of a differen...

Alexandra_Ivanova_1A

You're right, the mass of the products can't be more than the mass of the reactants due to The Law of Conservation of Mass (matter cannot be created or destroyed). Based on this, the mass of the products actually equals the mass of the reactants, as no change in mass occurs through a reaction. Produ...

Alexandra_Ivanova_1A

CuSO4 • 5H2O is a hydrate, yes. We include the water through both accounting for its contribution to the total molar mass of CuSO4 • 5H2O, as well as through the final volume. This is a dilution problem, so it is helpful to think of these sorts of problems (dilutions with hydrates) through how they ...

Alexandra_Ivanova_1A

Just to add on-- Crash Course on Youtube is great for conceptual chemistry and overarching themes, and really helps with understanding the "greater picture" when it comes to some concepts. If you are looking for more step-by-step instruction with worked out examples, I'd highly recommend u...

CHEMISTRY COMMUNITY

Search found 26 matches

Re: Final Exam Details and Review Sessions Winter 2017

Re: Post All Chemistry Jokes Here

Re: Post All Chemistry Jokes Here

Balancing (Acidic vs. Basic Balancing)

When to use reversible work equation?

Balancing Equations/When To Use Integers and When Not To?

8.53 / W=0 for Bomb Calorimeters ??

Re: Reaction Enthalpies HW Q49

Standard Enthalpy Question

Re: Homework Question 13.1

Re: Salts as Acids and Bases

Re: With respect to other compounds....

Re: Asterisks on the Table of Ligands [ENDORSED]

Trans- vs Cis- Complexes

Re: VESPR

Valence Electron Configuration

Re: Problem 3.65

Re: Electron Configuration video

Re: question 2.93

Re: Emit Light

Re: Rounding and Accuracy During Tests

Re: Question 1.33 (c) from the textbook [ENDORSED]

Rounding and Accuracy During Tests

Re: Limiting Reactant Audio-Visual Topic Question

Re: G #17 b

Re: Rusty on High School Chem [ENDORSED]