Search found 53 matches

by nelms6678
Sat Mar 17, 2018 8:23 pm
Forum: *Ketones
Topic: Ketones vs Aldehydes
Replies: 2
Views: 315

Ketones vs Aldehydes

When given line structures what should we look for that distinguishes a ketone from an aldehyde since they're pretty similar?
by nelms6678
Sat Mar 17, 2018 12:08 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Q7b Lyndon's Review
Replies: 6
Views: 219

Q7b Lyndon's Review

7b) Derive an expression for the rate of formation of the product E using the pre-equilibrium approach.

The unique rate was 1/2 d[E]/dt, why do we put a 1/2?
by nelms6678
Sat Mar 17, 2018 11:47 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Galvanic vs Concentration Cell
Replies: 2
Views: 118

Galvanic vs Concentration Cell

Is it true that for E values Galvanic should be positive and Concentration should always = 0?
by nelms6678
Thu Mar 15, 2018 12:30 pm
Forum: General Rate Laws
Topic: Test #3 Q5
Replies: 3
Views: 136

Re: Test #3 Q5

Also Q5 asked the question:
Given the instantaneous rate of rxn is 2.54x10^-2 mol/(Lxs), and intial mass of each reactant is 1.2g confined to a 750mL vessel, what is the rate constant of this reaction?

-What equation are we even using here?
by nelms6678
Thu Mar 15, 2018 12:24 pm
Forum: General Rate Laws
Topic: Test #3 Q5
Replies: 3
Views: 136

Test #3 Q5

CHCl3(g) + Cl2(g) ---> CCl4(g) + HClg(g)
The rate of the rxn was first order with respect to chlorine and trichloromethane.

What is the rate law?
by nelms6678
Thu Mar 15, 2018 12:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Delta Hc
Replies: 1
Views: 487

Delta Hc

An exam question asked for the value of delta H(c) with given values of 1.000 grams tropinone, heat capacity 25.950kj/C, and a temp increase from 25.262 C to 25.993.
The equations used were q = (Cv)(delta T) and then delta H(c) = q(rxn)/mols burned

What are these two equations?
by nelms6678
Wed Mar 14, 2018 11:10 am
Forum: First Order Reactions
Topic: Negative Orders
Replies: 5
Views: 254

Negative Orders

Can a reaction order be negative? If so, how?
by nelms6678
Wed Mar 14, 2018 11:07 am
Forum: General Rate Laws
Topic: Test #3 Q3
Replies: 3
Views: 448

Test #3 Q3

The rate of AB4 gas consumption in this Rxn is constant throughout and is given as 0.400M/s/ If your rxn vessel starts with 0.15M of B2C, how long will it take to get to 30.00M of B2C? AB4(g) + C2(g)---> AC2(g) + B2C(g) Can someone walk me through this, what do you do after you balance the equation?
by nelms6678
Wed Mar 14, 2018 10:29 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneity in gas equations [ENDORSED]
Replies: 1
Views: 82

Spontaneity in gas equations [ENDORSED]

If you're measuring spontaneity in the amount of moles of gas in an equation for example:
2 N2O(g)—> N2(g) + O2(g)

If the amount of moles are equal on both sides what does that tell about delta S?
by nelms6678
Tue Mar 13, 2018 4:50 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Value of Q
Replies: 1
Views: 99

Value of Q

When solving for Q, [P]/[R] what molecules are not including into equilibrium?
by nelms6678
Tue Mar 13, 2018 4:20 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Relationship between K and k
Replies: 2
Views: 183

Relationship between K and k

I understand the formula, but what is a more conceptual explanation between big K and little k?
by nelms6678
Mon Mar 12, 2018 10:22 pm
Forum: Phase Changes & Related Calculations
Topic: Test #1
Replies: 4
Views: 276

Test #1

3a) A tank of liquefied propane is punctured, emitting gaseous propane vapors. Is heat being transferred?
-Is this process releasing heat because the substance is undergoing a phase change? (liquid-->gas)
by nelms6678
Wed Mar 07, 2018 11:10 am
Forum: Balancing Redox Reactions
Topic: Test #2
Replies: 4
Views: 193

Re: Test #2

Then it asks is the rxn spontaneous?
Is it true that for spontaneity K<1?
by nelms6678
Wed Mar 07, 2018 11:10 am
Forum: Balancing Redox Reactions
Topic: Test #2
Replies: 4
Views: 193

Test #2

calculate the K of the following redox rxn:
Ag+(aq) + Cu(s) ---> Ag(s) + Cu2+(aq)

How would you start this problem?
by nelms6678
Wed Feb 28, 2018 10:20 am
Forum: First Order Reactions
Topic: After Integration [ENDORSED]
Replies: 3
Views: 148

After Integration [ENDORSED]

For the formula after we integrate it yields ln[A] = -k x t
Why is the k negative here, and should it be negative for a second order derivation as well?
by nelms6678
Mon Feb 26, 2018 3:59 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.25
Replies: 1
Views: 75

14.25

What is the reasoning behind why a more negative voltage has more strength? I thought a more positive charge will have more strength?
by nelms6678
Mon Feb 26, 2018 3:49 pm
Forum: Balancing Redox Reactions
Topic: Reversing Half-Reactions
Replies: 2
Views: 126

Reversing Half-Reactions

When reversing a Half-Rxn for example
Cu2+(aq) + 2e- ---> Cu(s) E=+0.34V
to Cu(s) ---> Cu2+(aq) + 2e-

why doesn't the value of E switch from positive to negative?
by nelms6678
Mon Feb 26, 2018 3:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Standard Potential
Replies: 4
Views: 168

Standard Potential

Does a standard potential of a cell occur under certain pH conditions?
Similar to the conditions 25 degrees celsius, 1 bar, etc.
by nelms6678
Mon Feb 26, 2018 3:32 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: log (Q)
Replies: 2
Views: 123

log (Q)

Is it always true that when log[Q]<1 the result will be negative and when log[Q]>1 the result will be positive?
by nelms6678
Tue Feb 13, 2018 5:58 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Equilibrium Equation
Replies: 1
Views: 76

Equilibrium Equation

In the equation delta G(r)= -RT ln(k)
what does k represent and is it the same as Q?
by nelms6678
Mon Feb 12, 2018 5:45 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Extensive vs Intensive
Replies: 3
Views: 141

Extensive vs Intensive

For an extensive property the larger the sample, the more heat is required to raise its temperature by a given amount. (Heat capacity)
What exactly is a definition for an intensive property? (Specific heat capacity)
by nelms6678
Mon Feb 12, 2018 4:40 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Open System
Replies: 5
Views: 328

Open System

An open system can exchange both matter and energy with the surrounding - what does it mean by matter is exchanged? Does anyone have an example?
by nelms6678
Sat Feb 10, 2018 1:08 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Total Entropy Change [ENDORSED]
Replies: 1
Views: 100

Total Entropy Change [ENDORSED]

The book states
When delta S (total) is positive, it is increasing and spontaneous
When delta S (total) is negative, it is decreasing and only the reverse is spontaneous
- Why is only the reverse spontaneous ?
by nelms6678
Sat Feb 10, 2018 1:06 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Exothermic/Endothermic [ENDORSED]
Replies: 3
Views: 172

Exothermic/Endothermic [ENDORSED]

Do exothermic and endothermic reactions relate to catabolism and anabolism ?

For example, in an exothermic reaction the formation of products is favored by lowering the temperature. Can this be thought as an example of catabolism or anabolism?
by nelms6678
Wed Feb 07, 2018 11:33 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Entropy Concept
Replies: 2
Views: 92

Entropy Concept

Does an endothermic reaction have the ability to increase spontaneity and entropy in reaction?
by nelms6678
Wed Feb 07, 2018 11:27 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.45
Replies: 3
Views: 148

9.45

Find the entropy of the surrounding and the system for:
Freezing of 1.00 lol C2H5OH

Would you use the equation delta H over T, just like if it were melting?
by nelms6678
Wed Feb 07, 2018 11:20 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.51 [ENDORSED]
Replies: 3
Views: 158

9.51 [ENDORSED]

Why are so many exothermic reactions spontaneous?

Using the Gibbs formula is it the negative delta G and delta H values that cause spontaneity?
by nelms6678
Tue Jan 23, 2018 5:23 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Monatomic Gas
Replies: 5
Views: 211

Monatomic Gas

For a monatomic gas the value is 3/2R, what is R’s value? Is it a constant or a rate?
by nelms6678
Tue Jan 23, 2018 5:06 pm
Forum: Calculating Work of Expansion
Topic: Natural Log
Replies: 1
Views: 70

Natural Log

Will there ever be an instance where the natural log of the volumes not be needed? I noticed some notations for irreversible work of expansion as w= -nRT(V2/V1) without the ln, is it just implied?
by nelms6678
Tue Jan 23, 2018 11:36 am
Forum: Administrative Questions and Class Announcements
Topic: Formula Sheet
Replies: 2
Views: 120

Formula Sheet

Is there a formula sheet that was posted? If so, is it on Chem. Community or the Class Website? Thanks
by nelms6678
Tue Jan 23, 2018 10:31 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Temperature
Replies: 3
Views: 115

Temperature

In Gibbs Free Energy, should we always use Kelvin, and is that because we want a positive value?
by nelms6678
Mon Jan 22, 2018 11:07 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: First Law Concept
Replies: 4
Views: 161

First Law Concept

I know that it is true for a closed system the internal energy changes as a function of heat & work, however, what about an open or isolated system? How does the first law apply to these two other systems?
by nelms6678
Mon Jan 22, 2018 11:02 am
Forum: Calculating Work of Expansion
Topic: Integral Equation
Replies: 2
Views: 99

Integral Equation

What do bounds V1 & V2 represent in the equation and also concecptually?
by nelms6678
Sat Dec 09, 2017 7:43 pm
Forum: Naming
Topic: Naming
Replies: 9
Views: 430

Naming

When would you use “ion” at the end of compound?
by nelms6678
Sat Dec 09, 2017 3:12 pm
Forum: DeBroglie Equation
Topic: Wavelike properties
Replies: 3
Views: 189

Wavelike properties

How can you tell if something has measurable wavelike properties?
by nelms6678
Sat Dec 09, 2017 3:08 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solutions
Replies: 1
Views: 154

Solutions

Practice Problem

How many grams of NaOH do you need to prepare a 3.00x10^2 mL stock solution of 2.00M NaOH?
---> 24.0g

So in the next set: How many milliliters of the stock solution would you need to make a 250 mL of 0.650M NaOH solution?
how would you do this problem?
by nelms6678
Sat Dec 09, 2017 3:02 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Paramagnetism
Replies: 3
Views: 299

Paramagnetism

What is the concept behind Paramagnetism?
by nelms6678
Sat Dec 09, 2017 12:01 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles
Replies: 3
Views: 210

Bond Angles

Does a tetrahedral shape always have 109.5 degree angles?
For what shapes are the angles >109.5 and <109.5 ?
by nelms6678
Fri Dec 08, 2017 11:37 pm
Forum: Electronegativity
Topic: Electronegativity of atoms
Replies: 3
Views: 260

Electronegativity of atoms

Does electronegativity refer to the value associated with atoms?
For example Group 1 is 1+, Group 2 is 2+, Group 13 is 3+, Group 15 3-, etc.
by nelms6678
Fri Dec 08, 2017 11:32 pm
Forum: Quantum Numbers and The H-Atom
Topic: Amount of Electrons [ENDORSED]
Replies: 6
Views: 254

Amount of Electrons [ENDORSED]

How many electrons in an atom can have the quantum numbers:
n=4, l=2, ml=+1, ms=+1/2

These quantum numbers represent the subshell 4d, so would it be 10 electrons ?
by nelms6678
Fri Dec 08, 2017 5:46 pm
Forum: Sigma & Pi Bonds
Topic: Sigma Bonds
Replies: 4
Views: 262

Re: Sigma Bonds

A Sigma bond is present in all single, double, and triple bonds.
Double and triple bonds are distinguished because they contain pi bonds.
by nelms6678
Fri Dec 08, 2017 5:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State Configuration
Replies: 3
Views: 139

Re: Ground State Configuration

Practice Problem

What is the full electron configuration for carbon in the ground state? How many unpaired electrons?
For the ground state would it be 1s^2 2s^2 2p^2 ?
And the for unpaired electrons are there 4?
by nelms6678
Fri Dec 08, 2017 5:39 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Ground State Configuration
Replies: 3
Views: 139

Ground State Configuration

Ground State Configuration

Fe^2+
I thought the ground state would be [Ar]3d^4 4s^2 because of its 2+ state?
by nelms6678
Fri Dec 08, 2017 5:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Naming of Ligands
Replies: 2
Views: 122

Naming of Ligands

What are the definitions of monodentate, bidentate, and tridentate?

In that case what makes NH2CH2CH2NH2 a bidentate?
by nelms6678
Fri Dec 08, 2017 5:15 pm
Forum: Lewis Structures
Topic: Lewis Structures
Replies: 2
Views: 153

Lewis Structures

Octet Rule

Why does the molecule NO2 not obey the octet rule?
Is it because of the lone pair that is placed on the central figure N?
by nelms6678
Fri Dec 08, 2017 2:49 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solutions
Replies: 5
Views: 263

Re: Solutions

Practice Question (pt.3)

How many milliliters of the stock solution would you need to make 250mL 0.650M NaOH solution?
Im not sure how to go about this problem? Any advice?
by nelms6678
Fri Dec 08, 2017 2:40 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solutions
Replies: 5
Views: 263

Re: Solutions

Practice Question (pt.2)

How many grams of NaOH do you need to prepare a 3.00 x 10^2 mL stock solution of 2.00M NaOH?

so first 2.00M x 3L which gives 0.6.
Why do you multiply this value by NaOH Molecular Weight (40.069)? Shouldn't you divide because of the formula MI VI = MF VF?
by nelms6678
Fri Dec 08, 2017 2:34 pm
Forum: Molarity, Solutions, Dilutions
Topic: Solutions
Replies: 5
Views: 263

Solutions

Practice Question: SOLUTIONS You need to make a stock solution of 0.0800M of sodium carbonate-Na2CO3 How much sodium carbonate would you add to a 250ml volumetric flask before filling to 250ml with water to make a 0.0800M aqueous solution of sodium carbonate? I know you should multiply 0.0800M x 25...
by nelms6678
Sat Nov 11, 2017 11:48 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Book Exercises
Replies: 3
Views: 87

Re: Book Exercises

4.22

Also unsure of the molecule IO6^5- shape I am getting an incorrect answer, any help?
by nelms6678
Sat Nov 11, 2017 11:45 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Book Exercises
Replies: 3
Views: 87

Book Exercises

4.26

Write the Lewis Structure and determine whether the molecule is polar or nonpolar.
SiO2

I got the Lewis Structure but am unsure what property makes it polar/nonpolar?
by nelms6678
Sun Oct 29, 2017 10:40 pm
Forum: DeBroglie Equation
Topic: Test 2, Question #7 [ENDORSED]
Replies: 5
Views: 392

Re: Test 2, Question #7 [ENDORSED]

Regarding the work posted above for part b of question #7-
So did you take (4.0*10^18) divided by 1/2(9.11*10^-31), then once you get that value square root it because velocity is V^2? I tried that and was unable to get 3.03*10^6
by nelms6678
Sun Oct 29, 2017 10:26 pm
Forum: DeBroglie Equation
Topic: Test 2, Question #7 [ENDORSED]
Replies: 5
Views: 392

Re: Test 2, Question #7 [ENDORSED]

Test 2, Question #5 Determine the frequency of the emitted photon when an electron in a hydrogen atom drops from the quantum state of n=3 to n=1. I used the formula -hR/n^2 and calculated: n=3... -1/9hR = -2.42x10^-19 n=1... -1hR = -2.18x10^-18 Using these two values I then used N(final)-N(intial),...
by nelms6678
Sat Oct 07, 2017 9:13 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: E.15 [ENDORSED]
Replies: 10
Views: 672

Re: E.15 [ENDORSED]

An example from section "E"
What mass of NaHSO4 should you weigh out to obtain .20 mol NaHSO4?

How would you start this problem off? Im confused would this be Mass Percentage Comp.?

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