Search found 64 matches

by jillianh1B
Tue Feb 12, 2019 2:50 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4.15 7th ed
Replies: 1
Views: 15

4.15 7th ed

Why can you not use mc(delta)T=-mc(delta)T to solve this?? I keep getting 298 (if i use kelvin) and 25 (if i use celsius) as my answer.
by jillianh1B
Tue Feb 12, 2019 1:40 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: free expansion
Replies: 2
Views: 12

free expansion

can someone describe the characteristics of free expansion? Is it just that w=0, and therefore q and deltaU are zero? Thank you!
by jillianh1B
Tue Feb 12, 2019 1:39 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: expansion of ideal gas
Replies: 1
Views: 4

expansion of ideal gas

When calculating the total entropy change for the expansion of an ideal gas, why can we assume that deltaU=0 and therefore q=-w? I don't understand the logic behind this and may be missing something.
by jillianh1B
Tue Feb 12, 2019 1:37 am
Forum: Calculating Work of Expansion
Topic: 0 work vs no work
Replies: 4
Views: 30

0 work vs no work

Is there a difference between specifying that there is no work versus 0 work? I was confused why the solutions manual put those as two separate answers when regarding situations in question 4.13.9 (a) and (b).
by jillianh1B
Tue Feb 12, 2019 1:36 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: system v surroundings entropy
Replies: 2
Views: 20

system v surroundings entropy

I know we use deltaH/T to calculate the delta S of both system and surroundings. I also know that Ssys=-Ssurr. Does it matter whether the system or surroundings side is negative? It seems to me like it shouldn't make a difference if the system is reversible, but the book always make Ssurr negative o...
by jillianh1B
Tue Feb 12, 2019 1:32 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy change
Replies: 2
Views: 8

entropy change

Why is entropy change smaller at higher temperatures? Does this only occur in special circumstances?
by jillianh1B
Tue Feb 12, 2019 1:28 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: hess law equations
Replies: 3
Views: 19

hess law equations

On the midterm, will we be expected to know how to write out the equations that we will use to utilize Hess's law? Like in book problem 4D15? If so, can someone explain going about that?
by jillianh1B
Tue Feb 12, 2019 1:23 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: assuming no work
Replies: 2
Views: 13

assuming no work

When can you assume that no work is done on a system so that deltaU=heat?
by jillianh1B
Sat Feb 09, 2019 11:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard reaction enthalpy vs reaction enthalpy
Replies: 1
Views: 9

standard reaction enthalpy vs reaction enthalpy

is there a difference between standard reaction enthalpy and reaction enthalpy? I don't understand why you have to use Hess's Law for 4D15 but not for 4D17, and they use the different wording. thank you!
by jillianh1B
Thu Feb 07, 2019 12:23 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Enthropy
Replies: 2
Views: 32

Re: Enthropy

In some problems, it will also specify whether or not these values are constant.
by jillianh1B
Thu Feb 07, 2019 12:23 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Determining Spontaneity of a Reaction
Replies: 4
Views: 24

Re: Determining Spontaneity of a Reaction

The LA in a review session I went to today also said that Gibbs free energy, or delta G, is a concept that helps us determine spontaneity. We haven't learned about it yet in lecture, but I think this would be a good reference point for your question.
by jillianh1B
Thu Feb 07, 2019 12:21 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Negative q
Replies: 7
Views: 26

Re: Negative q

A negative q value stands for negative heat. This corresponds to vaporization and melting.
by jillianh1B
Tue Jan 29, 2019 4:08 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question 5H1
Replies: 2
Views: 17

Re: Question 5H1

Thank you for this reply! After looking back and comparing your answer to some high school notes, this would have been a lifesaver.
by jillianh1B
Tue Jan 29, 2019 4:07 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: ICE
Replies: 14
Views: 40

Re: ICE

The E is the final step in an ice chart. It adds up the I and C steps and it is what you will put into an equation to get your x value when given K.
by jillianh1B
Tue Jan 29, 2019 4:02 pm
Forum: Ideal Gases
Topic: Q and K
Replies: 9
Views: 37

Re: Q and K

Q is calculated with values that are at any point in the reaction. We can use our answer from Q and compare to to the constant K value to determine whether the reaction will proceed forward or reverse.
by jillianh1B
Wed Jan 23, 2019 10:10 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: buffers
Replies: 1
Views: 18

buffers

Can someone define what a buffer is and the significance of it in calculations?
by jillianh1B
Wed Jan 23, 2019 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: predict solubility
Replies: 2
Views: 21

predict solubility

How can we use equilibrium constants to predict solubility?
by jillianh1B
Mon Jan 21, 2019 11:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 7th ed 5I19
Replies: 1
Views: 11

Textbook 7th ed 5I19

I don't understand why in this question the solutions manual uses 0.80 as the x value without using the quadratic formula or anything. Can someone explain why it is like this?
by jillianh1B
Mon Jan 21, 2019 11:01 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE chart
Replies: 3
Views: 14

ICE chart

Can both molar values and concentrations go into the ice chart? I have seen it used both ways in the homework and it was confusing me.
by jillianh1B
Mon Jan 21, 2019 11:00 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Question 5H1
Replies: 2
Views: 17

Question 5H1

The concept presented in this question is confusing me. Why is part b considered the square root of the original equation? In part c, how it is the square of the original equation if 3^2 is 9?
by jillianh1B
Mon Jan 21, 2019 10:56 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Thermodynamically Favorable
Replies: 2
Views: 23

Thermodynamically Favorable

How do you determine which product or which reactant is more favorable based on the K value? This question is referring to 7th edition 5H13 part C. Thank you!
by jillianh1B
Wed Jan 16, 2019 11:40 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Textbook 7th edition 6E1
Replies: 1
Views: 20

Textbook 7th edition 6E1

I have a couple questions about this question that are confusing me. Why do we need to be doing this set up at all if H2So4 is a strong acid? I thought we did the ICE chart for weak acids? Does this relate to why there is a "second ionization in the solutions manual? What is that? Lastly, Where...
by jillianh1B
Mon Jan 14, 2019 10:36 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ksp
Replies: 2
Views: 27

Ksp

I remember discussion a Ksp constant in high school and was wondering if anyone else was familiar with it and if it is something we have already discussed in class. Can anyone explain or define it? Thanks!
by jillianh1B
Mon Jan 14, 2019 10:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure [ENDORSED]
Replies: 2
Views: 23

Pressure [ENDORSED]

Can someone explain the significance of pressure when discussing equilibrium constants? For example, how would adding an inert gas to a system at equilibrium change anything?
by jillianh1B
Mon Jan 14, 2019 10:23 pm
Forum: Ideal Gases
Topic: Water
Replies: 9
Views: 61

Water

I was wondering in class today- is water always a liquid in equations? Can it ever be aqueous? If not, why not?
by jillianh1B
Thu Jan 10, 2019 3:45 pm
Forum: Ideal Gases
Topic: Equilibrium Constant
Replies: 3
Views: 49

Re: Equilibrium Constant

Both gaseous and aqueous reactants and products can be used when calculating K or Q. We cannot use solids or liquids as they do not effect the amount of products or reactants at all, so we keep them at value=1.
by jillianh1B
Thu Jan 10, 2019 3:43 pm
Forum: Ideal Gases
Topic: Equilibrium Constant and Reaction Quotient
Replies: 3
Views: 16

Re: Equilibrium Constant and Reaction Quotient

The equilibrium constant is K and Q is the reaction quotient. While they are calculated the same way ([products]/[reactants]), they are different. Q is the quantity of products and reactants that actually changes as the system approaches equilibrium. K is the numerical value of Q at the end of the r...
by jillianh1B
Wed Jan 09, 2019 9:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: how to write the formula for K
Replies: 6
Views: 37

how to write the formula for K

I noticed in the solutions manual that when writing the equation for the K value, the concentrations were always written as the reactant or product as a subscript of P. Do we have to write it like that? I don't want to lose credit on my homework for that. Thank you!
by jillianh1B
Sat Dec 08, 2018 11:03 pm
Forum: Formal Charge and Oxidation Numbers
Topic: #21 on churro Qs
Replies: 1
Views: 36

#21 on churro Qs

Referring to #21 on churro questions ("The overall molecule as shown is neutral. What is the oxidation state of the iron?") Can someone explain to me why the answer is +2? When I added up all of the formal charges for the surrounding N atoms, I got +6, and I don't understand how a +2 charg...
by jillianh1B
Sat Dec 08, 2018 9:19 pm
Forum: Quantum Numbers and The H-Atom
Topic: Why is this statement incorrect?
Replies: 3
Views: 21

Why is this statement incorrect?

A question from the midterm identified the statement "the lowest value that the magnetic quantum number ml can take is -9" as incorrect. Can someone explain WHY it is incorrect?
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by jillianh1B
Sat Dec 08, 2018 9:18 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: ranking strong bases
Replies: 2
Views: 20

ranking strong bases

how would we go about ranking strong bases? what is the first thing we should look for when doing so?
by jillianh1B
Fri Dec 07, 2018 12:16 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Ranking strong acids and bases
Replies: 4
Views: 35

Ranking strong acids and bases

How would you go about ranking which strong acid is stronger or which strong base is stronger? For example, how would you compare HI and HClO4 or Ca(OH)2 and KOH?
by jillianh1B
Tue Dec 04, 2018 4:03 pm
Forum: Hybridization
Topic: bond angles
Replies: 2
Views: 19

Re: bond angles

I think concerning bond angles, you are better off memorizing them specific to their shape.
by jillianh1B
Tue Dec 04, 2018 4:01 pm
Forum: Hybridization
Topic: Radical Placement
Replies: 3
Views: 23

Radical Placement

When you have a radical, how do you know where to place the one extra electron? Is it just in the place that would ensure the most stability about the central atom?
by jillianh1B
Tue Dec 04, 2018 4:00 pm
Forum: Hybridization
Topic: Hybridization of p orbitals
Replies: 3
Views: 39

Re: Hybridization of p orbitals

I thought that two p orbitals could hybridize with a pi bond.
by jillianh1B
Wed Nov 28, 2018 2:14 pm
Forum: Hybridization
Topic: Biological Importance
Replies: 1
Views: 16

Biological Importance

What is the biological importance of hybridization? When and where is it most likely to occur?
by jillianh1B
Wed Nov 28, 2018 2:13 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 34

Re: Bond Angles

I have found that googling "VSEPR Chart" brings up great charts that you can help use to memorize these bond angles. Some can be inferred, but many, in my opinion, should just be memorized.
by jillianh1B
Mon Nov 19, 2018 12:47 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bent vs. Angular
Replies: 3
Views: 35

Re: Bent vs. Angular

It is important to understand, though, that while the names are interchangeable, there are bent shapes for structures with three and four areas of electro density. Follow the pictured bond angles when recognizing the difference.
by jillianh1B
Mon Nov 19, 2018 12:44 pm
Forum: Octet Exceptions
Topic: The center atom
Replies: 20
Views: 204

Re: The center atom

Here is the correct lewis structure for HClO.
by jillianh1B
Mon Nov 19, 2018 12:43 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Polarizability v. Polarizing Power
Replies: 2
Views: 70

Re: Polarizability v. Polarizing Power

I find it helpful to separate their definitions. I think that a cation has a plus sign, so it's fitting that polarizing power has one more word than polarizability. Polarizability is therefore associated with anions, and polarizing power with cations.
by jillianh1B
Tue Nov 13, 2018 3:25 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Molecular Shape
Replies: 6
Views: 43

Re: Molecular Shape

We learned about the wedge and dash model in discussion today. The wedge represents the idea that the atom is coming out at you, and the dashes represent the atom falling behind the structure. This model is just a way to interpret the shape in your head.
by jillianh1B
Tue Nov 13, 2018 3:18 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Names and Shapes of molecules
Replies: 2
Views: 25

Re: Names and Shapes of molecules

My TA told us to be familiar with linear, trigonal planar, angular (bent), tetrahedral, trigonal pyramidal, trigonal bi-pyramidal, seesaw, T-shaped, octahedral, square planar, and square pyramidal. You need to also know bond the different bond angles for each of these and understand the fact that st...
by jillianh1B
Fri Nov 02, 2018 11:35 pm
Forum: Lewis Structures
Topic: checking your answer
Replies: 2
Views: 33

checking your answer

I've found that when I draw out structures, even if I have all of the valence electrons represented and correct, I will still get the structure wrong. I know this is because I need to make my structure have a formal charge close to 0. But, how can I be sure that it is the most stable it can be? How ...
by jillianh1B
Tue Oct 30, 2018 10:41 pm
Forum: Electronegativity
Topic: Electronegativity vs Electron Affinity [ENDORSED]
Replies: 1
Views: 61

Electronegativity vs Electron Affinity [ENDORSED]

My TA tried to explain to us today about the difference, but it was hard to understand with the given definitions. Can someone explain the difference better and give an example comparing two elements?
by jillianh1B
Tue Oct 30, 2018 10:39 pm
Forum: Resonance Structures
Topic: How does a resonance structure work?
Replies: 10
Views: 170

Re: How does a resonance structure work?

An important thing to remember about resonance structures, along with the above definitions, is that all of the bonds in the Lewis Structure have the same length. This displays that drawing resonance is just a way of showing that all of the bonds have the same length no matter where they are placed.
by jillianh1B
Tue Oct 30, 2018 10:37 pm
Forum: Formal Charge and Oxidation Numbers
Topic: Finding the lowest energy structure
Replies: 5
Views: 75

Re: Finding the lowest energy structure

I think that this is the most efficient way and only way to be completely sure of stability.
by jillianh1B
Wed Oct 24, 2018 10:05 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ordering of electrons in d-shell
Replies: 2
Views: 25

Ordering of electrons in d-shell

How important is it to put, for example, 3d10 before 4s1? Does order matter even though you are conveying the same information? Are there any exceptions? Thanks!
by jillianh1B
Wed Oct 24, 2018 10:04 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground vs Excited State
Replies: 3
Views: 60

Re: Ground vs Excited State

Hund's Rule is important to remember in answering this: every orbital must be filled in order for any of them to be doubly occupied. If you ever see two electrons in one orbital, two in the second and none in the third, or a diagram where one arrow is pointing up, one down, and then one up (in case ...
by jillianh1B
Wed Oct 24, 2018 10:01 pm
Forum: Properties of Light
Topic: Using a rounded speed of light in EM problems
Replies: 4
Views: 113

Re: Using a rounded speed of light in EM problems

I always have literally typed 3E8 in my calculator and have never had a problem with it. Also, if you have a TI 36 calculator, there is a constants section that has the full number in there, so I use that a lot too.
by jillianh1B
Mon Oct 15, 2018 10:46 am
Forum: Properties of Electrons
Topic: Constructive vs Destructive
Replies: 3
Views: 47

Constructive vs Destructive

Can someone explain the difference between constructive and destructive waves and why they are important in determining the properties of an electron? How are they unique?
Thank you!
by jillianh1B
Mon Oct 15, 2018 10:45 am
Forum: Properties of Light
Topic: List Of Equations
Replies: 2
Views: 38

List Of Equations

Does anyone have a helpful list of equations that pertain to this unit? I've been trying to compile one, but lose track of units and constants. If anyone could post a complete list (with labeled constants), that would be very helpful!
Thank you!
by jillianh1B
Mon Oct 15, 2018 10:44 am
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Incorrect Atomic Model
Replies: 6
Views: 86

Incorrect Atomic Model

Today in class we discussed an "incorrect atomic model" situation worded like this: AN electron is located inside the nucleus of an atom. For H-atoms, the electron is confined to its nuclear diameter, 1.7*10^-15 m. The process to get to the answer, which was 3.4*10^10 m/s, was very confusi...
by jillianh1B
Mon Oct 15, 2018 10:41 am
Forum: Molarity, Solutions, Dilutions
Topic: Units?
Replies: 8
Views: 126

Re: Units?

I've found that it depends on both the question and the units that were given in the question. Whether your answer is in liters or mL doesn't matter as long as it isn't specified in the question. I like to stick to liters, as the units for molarity are mol/L.
by jillianh1B
Sat Oct 13, 2018 1:09 pm
Forum: Properties of Light
Topic: frequencies and wavelength
Replies: 5
Views: 54

Re: frequencies and wavelength

Anjali_Kumar3E wrote:In the formula E=hv what does the letter v respresent? I know E is energy and h is a given number which is the constant but what is v.

V represents velocity of the particle.
by jillianh1B
Sat Oct 13, 2018 1:09 pm
Forum: Properties of Light
Topic: frequencies and wavelength
Replies: 5
Views: 54

Re: frequencies and wavelength

V represents the velocity of the object.
by jillianh1B
Sat Oct 13, 2018 1:07 pm
Forum: Photoelectric Effect
Topic: Work function
Replies: 3
Views: 35

Re: Work function

I think workforce may be a term he used in class in reference to physics as part of an example? I could be wrong.
by jillianh1B
Sat Oct 13, 2018 1:06 pm
Forum: DeBroglie Equation
Topic: Wavelike Properties
Replies: 2
Views: 37

Wavelike Properties

How do you tell if an object has wavelike properties? Is it solely based on the answer?
by jillianh1B
Sun Oct 07, 2018 6:55 pm
Forum: Balancing Chemical Reactions
Topic: Where to start [ENDORSED]
Replies: 10
Views: 236

Where to start [ENDORSED]

When balancing, where does everyone start? Does everyone always balance the one that occurs the least first? I was wondering if there are any other methods that people use because I have had trouble with balancing equations for a while. Thanks!
by jillianh1B
Sun Oct 07, 2018 6:53 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: diatomic elements
Replies: 12
Views: 246

Re: diatomic elements

In high school, we learned to remember them with a phrase pronounced "Br-inkl-hoff," which is Br(bromine), I(iodine), N (nitrogen), Cl(chlorine), H(hydrogen), O(oxygen), and F(fluorine). Helped me a lot back then and now.
by jillianh1B
Sun Oct 07, 2018 6:48 pm
Forum: Balancing Chemical Reactions
Topic: Extensive v. Intensive Property [ENDORSED]
Replies: 6
Views: 144

Re: Extensive v. Intensive Property [ENDORSED]

In class, I wrote in my notebook, in simple terms, that with extensive properties, the scale of the matter is important (volume), and with intensive properties, the amount doesn't matter (density).
by jillianh1B
Sun Oct 07, 2018 6:46 pm
Forum: Empirical & Molecular Formulas
Topic: HW F11
Replies: 4
Views: 91

Re: HW F11

Just wondering, is it important that we learn all of the polyatomic ions for the first test/subsequent tests? I know a few, but is there a list somewhere of ones we should memorize or something? Thanks!
by jillianh1B
Sun Oct 07, 2018 6:44 pm
Forum: SI Units, Unit Conversions
Topic: formula units [ENDORSED]
Replies: 68
Views: 20030

Re: formula units [ENDORSED]

This thread is similar to a question I jsut asked. I'm just confused on when to use formula units and when to use other names, like ions, atoms, or molecules? Thanks!
by jillianh1B
Sun Oct 07, 2018 6:42 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Forumula Units?
Replies: 2
Views: 80

Forumula Units?

I'm a little bit confused on when to use formula units, atoms, or molecules. How do you know which one to use and when? Are there certain compounds specific to each one? I came upon this question when doing question 9E in the 7th edition book.
Thank you!

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