Search found 42 matches

by Tia Tomescu 2D
Sun Mar 18, 2018 10:13 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: arrhenius
Replies: 1
Views: 195

Re: arrhenius

The Vant Hoff equation comes by setting the two delta G equations as equal.
by Tia Tomescu 2D
Sun Mar 18, 2018 10:11 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: metal dissolved
Replies: 2
Views: 216

Re: metal dissolved

If delta G is negative then the reaction will occur.
by Tia Tomescu 2D
Sun Mar 18, 2018 10:10 pm
Forum: Student Social/Study Group
Topic: I wanted to make a good chemistry joke...
Replies: 2
Views: 335

Re: I wanted to make a good chemistry joke...

Helium. Helium. Helium.
by Tia Tomescu 2D
Sun Mar 18, 2018 10:08 pm
Forum: General Science Questions
Topic: Grade
Replies: 8
Views: 741

Re: Grade

As far as I know, the class is not graded.
by Tia Tomescu 2D
Sat Mar 17, 2018 2:01 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Calculating Q and K
Replies: 1
Views: 1498

Calculating Q and K

When calculating Q and K will can molarity and pressure be used interchangeably?
by Tia Tomescu 2D
Sat Mar 17, 2018 1:53 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Test 2 Q7
Replies: 3
Views: 261

Re: Test 2 Q7

I think you have to use deltaG=-nFE to calculate this.
by Tia Tomescu 2D
Sat Mar 17, 2018 1:50 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First Law Thermo
Replies: 4
Views: 258

Re: First Law Thermo

No because the first law is deltaU = q + w and but equation you have is only related to q.
by Tia Tomescu 2D
Sat Mar 17, 2018 11:45 am
Forum: Balancing Redox Reactions
Topic: Lyndon Review session Q3
Replies: 1
Views: 175

Lyndon Review session Q3

Q3) Mn2+ (aq) + Br2 (l) → MnO4- (aq) + Br- (aq) Balance the redox reaction. Is the correct answer 8(H2O) + 2(Mn2)+ + 5(Br2) --> 16(H+) + 2(MnO4-) + 10(Br-) ?
by Tia Tomescu 2D
Wed Mar 14, 2018 11:03 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Calculating Work
Replies: 2
Views: 139

Calculating Work

Question: A balloon filled with 31.9 mol of Helium has a volume of 876 L at 0oC and 1.00 atm pressure. At constant pressure, the temperature of the balloon is suddenly increased to 38.0oC , causing the balloon to expand to a volume of 998L. (The molar heat capacity of Helium is 20.8 J/ oC mol) How m...
by Tia Tomescu 2D
Wed Mar 14, 2018 10:30 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: isolated system after time
Replies: 2
Views: 247

isolated system after time

If an isolated system contained +100 kJ of energy, after 100 years why will the internal energy be 0? (UA workshop week 2 question 3)
by Tia Tomescu 2D
Sun Mar 04, 2018 4:14 pm
Forum: First Order Reactions
Topic: Deriving these Equations
Replies: 7
Views: 274

Re: Deriving these Equations

[A] is concentration (at any time), and [A]0 is concentration at t=0.
by Tia Tomescu 2D
Sun Mar 04, 2018 4:12 pm
Forum: General Rate Laws
Topic: Independent of the rate
Replies: 2
Views: 135

Re: Independent of the rate

Basically, if the reaction will proceed even with a little bit of reactant and will not make more or less product if you increase or decrease the concentration of reactants then it is independent of the rate.
by Tia Tomescu 2D
Sun Mar 04, 2018 4:06 pm
Forum: First Order Reactions
Topic: Second Order Half Life Equation
Replies: 2
Views: 112

Second Order Half Life Equation

How did we get 0.693 in the equation?
by Tia Tomescu 2D
Sat Feb 24, 2018 5:06 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic cell set up
Replies: 8
Views: 275

Re: Galvanic cell set up

To add on to that, in real life situations the left might not be the anode, it is just standardized like so in textbooks so that it is easier to comprehend.
by Tia Tomescu 2D
Sat Feb 24, 2018 5:03 pm
Forum: General Rate Laws
Topic: Units for 15.3 Part B
Replies: 4
Views: 214

Re: Units for 15.3 Part B

I believe the (mol O2) is just to specify that the answer is for the moles of O2. Usually when we answer questions we don't need to specify that.
by Tia Tomescu 2D
Sat Feb 24, 2018 4:57 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: kinetics
Replies: 5
Views: 303

Re: kinetics

Both are studying reactions, but thermodynamics is only concerned with the initial and final states while kinetics factors in the speed of the reaction--their rates.
by Tia Tomescu 2D
Sun Feb 11, 2018 5:49 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: entropy of vaporization
Replies: 1
Views: 98

Re: entropy of vaporization

You can calculate it through a series of steps.

1) Increase temperature from 25 C to 100 C
2) Find the enthalpy of vaporization of water (l -->g)
3) Lower the temperature of the water vapor from 100 C to 25C

Hope that helped!
by Tia Tomescu 2D
Sun Feb 11, 2018 2:59 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.13
Replies: 3
Views: 139

Re: 9.13

Page 281 of the textbook gives a good summary of the Cp and Cv for atoms, linear molecules, and nonlinear molecules.
by Tia Tomescu 2D
Sun Feb 11, 2018 2:56 pm
Forum: Balancing Redox Reactions
Topic: nernst eq'n
Replies: 2
Views: 97

Re: nernst eq'n

Yes, it is the number of moles of electrons.
by Tia Tomescu 2D
Sun Feb 04, 2018 9:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta G°
Replies: 5
Views: 162

Re: Delta G°

Looking at the equation deltaG°=-RTlnK, if K=1, that means the products and reactants are of the same concentration, and thus lnK=0, and deltaG° will equal 0.
by Tia Tomescu 2D
Sun Feb 04, 2018 9:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: thermodynamically favored
Replies: 6
Views: 747

Re: thermodynamically favored

Thermodynamically favored means the reaction will proceed spontaneously, and it refers to deltaG, the free energy.
by Tia Tomescu 2D
Sun Jan 28, 2018 1:46 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Internal Energy and Spontaneity
Replies: 3
Views: 109

Re: Internal Energy and Spontaneity

To add on to that, the system is at equilibrium when entropy is at a maximum.
by Tia Tomescu 2D
Sun Jan 28, 2018 1:40 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 9.13
Replies: 3
Views: 165

Re: 9.13

Because pressure is increased so we can't use the second equation (Cv is at constant pressure!)
by Tia Tomescu 2D
Sun Jan 28, 2018 1:35 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Spontaneous Processes for Entropy
Replies: 2
Views: 201

Re: Spontaneous Processes for Entropy

Yes, when the value of entropy is positive the process is spontaneous. The equation just spells this out in math. It it true that when V2 is larger than V1, there are more possible positions, so entropy is positive. (spontaneous reaction) But V2 can also be smaller than V1 in which case the equation...
by Tia Tomescu 2D
Sat Jan 20, 2018 10:04 pm
Forum: Phase Changes & Related Calculations
Topic: HW #3
Replies: 3
Views: 152

Re: HW #3

I think there still might be concept questions relating to the topic, but just not calculations.
by Tia Tomescu 2D
Sat Jan 20, 2018 10:01 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Perfect Isolated System
Replies: 3
Views: 140

Re: Perfect Isolated System

It could be argued that the universe is a "perfectly" isolated system!
by Tia Tomescu 2D
Sat Jan 20, 2018 9:06 pm
Forum: Calculating Work of Expansion
Topic: Work done on / work done by system
Replies: 5
Views: 205

Work done on / work done by system

Could anyone explain to me they difference between work done on the system and work done by the system? I have trouble grasping the concept of work and the system.
by Tia Tomescu 2D
Sat Jan 13, 2018 7:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Possible Error in Question 8.55 (Hess' Law)
Replies: 4
Views: 224

Re: Possible Error in Question 8.55 (Hess' Law)

This is a good observation, I do not have a solution manual, but when I solved this question I did this: (-1107)(-3/2)+(-1676)=15.5kJ which rounds to 16kJ. This is the correct answer in the answer manual. But in fact, the oxygen will not be canceled out. The product side will have 3/2 O2 and the rea...
by Tia Tomescu 2D
Sat Jan 13, 2018 6:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework Question 8.63 (c)
Replies: 2
Views: 136

Homework Question 8.63 (c)

I checked my equations many times, but my value always comes to -38.72kJ while the answer is 15.28kJ. The previous two questions, (a) and (b) are similar to (c) and I used the same method: enthalpy of products - enthalpy of reactants. Does anyone know how to solve this?
by Tia Tomescu 2D
Sat Jan 13, 2018 4:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Sig Figs for Question 8.45 (a)
Replies: 5
Views: 212

Sig Figs for Question 8.45 (a)

My answer was 448.5 which I rounded to 449. But the answer was 448. Does anyone know why?
by Tia Tomescu 2D
Thu Dec 07, 2017 2:51 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Formic Acid and Acetic Acid
Replies: 2
Views: 329

Formic Acid and Acetic Acid

Why is Formic acid a stronger acid than Acetic?
by Tia Tomescu 2D
Thu Dec 07, 2017 2:49 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: 12.53 Names of acidic compounds
Replies: 2
Views: 199

12.53 Names of acidic compounds

I noticed in 12.53 only the names of the compounds were given. Are we supposed to know the formulas by heart?
by Tia Tomescu 2D
Mon Dec 04, 2017 8:01 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: F and Cl in acids
Replies: 2
Views: 170

F and Cl in acids

Why is HF a weak acid and HCl a strong one, while C2O2HF3 is a stronger acid than C2O2HCl3?
by Tia Tomescu 2D
Wed Nov 15, 2017 9:34 pm
Forum: Hybridization
Topic: Polar/nonpolar [ENDORSED]
Replies: 14
Views: 1455

Re: Polar/nonpolar [ENDORSED]

Nicole, yes, that is true for polar molecules.
by Tia Tomescu 2D
Wed Nov 08, 2017 1:41 pm
Forum: Trends in The Periodic Table
Topic: Hydrogen Electronegativity
Replies: 4
Views: 1094

Hydrogen Electronegativity

Why does hydrogen have a relatively high electronegativity?
by Tia Tomescu 2D
Thu Nov 02, 2017 10:21 am
Forum: Electronegativity
Topic: Finding Electronegativity
Replies: 4
Views: 255

Re: Finding Electronegativity

Also, just to add, the common Electronegativity chart that we use now is based on the Pauling's scale, which I believe uses the disassociation energy of diatomic bonds to calculate the disassociate energy of a molecule if it were a purely covalent bond. Then it measures the difference between the ac...
by Tia Tomescu 2D
Mon Oct 30, 2017 2:53 pm
Forum: Trends in The Periodic Table
Topic: Fluorine's Formal Charge
Replies: 1
Views: 233

Fluorine's Formal Charge

Today in lecture Professor Lavelle said that Fluorine's formal charge cannot be +1 because it is highly unstable. Why is this?
by Tia Tomescu 2D
Sun Oct 22, 2017 3:27 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: nodal planes [ENDORSED]
Replies: 3
Views: 414

Re: nodal planes [ENDORSED]

Based off of the homework questions in the textbook, believe we need know how many nodal planes there are for the s p d orbitals. (However, if you look at the assigned homework, questions regarding the nodal planes were skipped.)
by Tia Tomescu 2D
Sat Oct 21, 2017 5:58 pm
Forum: Properties of Light
Topic: Mathematical Error with 1.55 (a) [ENDORSED]
Replies: 2
Views: 294

Mathematical Error with 1.55 (a) [ENDORSED]

This is what I did:

v/c=3600cm^-1
v/c=36m^-1
v=36 x c
v=36 x 3x10^8
v=1.1x10^10 (1/s)

Yet the answer is 1.1x10^14 (1.s)

Does anyone know what went wrong with my method?
by Tia Tomescu 2D
Wed Oct 11, 2017 10:14 pm
Forum: Properties of Light
Topic: Question 1.15 Rydberg Equation Math Problem
Replies: 1
Views: 133

Question 1.15 Rydberg Equation Math Problem

1.15 In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. I used \frac{1}{\lambda }=R_{H}(\frac{1}{n1^2}-\frac{1}{n2^2})...
by Tia Tomescu 2D
Wed Oct 04, 2017 7:33 pm
Forum: Significant Figures
Topic: E29 (d) Significant Figures
Replies: 3
Views: 337

E29 (d) Significant Figures

For Question E29, the question only gives a number with 3 significant figures (8.61), yet the answer for (d) on the textbook is 4 sig figs (0.3099). Does anyone know why?
by Tia Tomescu 2D
Wed Oct 04, 2017 5:22 pm
Forum: Molarity, Solutions, Dilutions
Topic: L7 Help
Replies: 4
Views: 362

Re: L7 Help

In my opinion, L7 (b) states "What mass of oxygen is needed to oxidize this amount of tristearin?" Since they're asking for the same amount (454g), you should still continue using 454g as the amount of tristearin to solve the problem.

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