Search found 25 matches

by Charlene Tang 1B
Thu Mar 10, 2016 6:58 pm
Forum: Zero Order Reactions
Topic: Determining zero order reactions
Replies: 1
Views: 322

Re: Determining zero order reactions

Plot t against [A], and if you get a straight line with negative slope, it's zero order.

Hope this helps! :)
by Charlene Tang 1B
Tue Mar 01, 2016 9:08 pm
Forum: *Cycloalkanes
Topic: Naming Structures
Replies: 2
Views: 449

Naming Structures

If there's a cyclopentane with 2 methyl groups attached to one of the carbons and 1 isopropyl group attached to the carbon next to that, would the name of the structure be 1-isopropyl-2,2-dimethylpentane? This is number 16 on chapter 1 of the Ochem book and the answer key says the answer is 2-isopro...
by Charlene Tang 1B
Thu Feb 25, 2016 6:15 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Finding K
Replies: 2
Views: 375

Re: Finding K

I'm going to assume the K for the overall reaction is the K for the forward reaction. If you're given the K (equilibrium constant) for the reverse reaction, all you need to do is just 1/K reverse to get the K forward . If K is large (or just >1), then concentration of the products is larger than tha...
by Charlene Tang 1B
Thu Feb 18, 2016 11:08 am
Forum: General Rate Laws
Topic: What is the "unique rate of reaction"?
Replies: 1
Views: 829

Re: What is the "unique rate of reaction"?

A unique rate is the rate of appearance/disappearance of any of the species in a reaction divided by its stoichiometric coefficient. Since the coefficients aren't taken into account in the average rate, it might be different from the unique rate.

Hope this helps!
by Charlene Tang 1B
Sun Feb 14, 2016 6:25 pm
Forum: Second Order Reactions
Topic: Slope of a Second Order Reaction Plot
Replies: 1
Views: 1208

Re: Slope of a Second Order Reaction Plot

The positivity/negativity of the slope has nothing to do with concentration, but rather the order of the reaction. We can use the 2nd order differential rate law to obtain (-1/a)(d[A]/dt)=k[A]^2 --> (-d[A]/[A]^2) = kdt When you integrate that you'll get 1/[A] = kt + 1/[A] o , and when you plot 1/[A]...
by Charlene Tang 1B
Fri Feb 05, 2016 11:03 am
Forum: Calculating Work of Expansion
Topic: When to use which formula
Replies: 3
Views: 534

When to use which formula

When do we know to use w=-nRTln(V2/V1) rather than w=-P∆V?
by Charlene Tang 1B
Tue Jan 26, 2016 12:20 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: When to use R or C?
Replies: 1
Views: 456

When to use R or C?

This is 9.13 on the homework. During the test of an internal combustion engine, 3.00 L of nitrogen gas at 18.5 C was compressed suddenly (and irreversibly) to 0.500 L by driving in a piston. In the process, the temperature of the gas increased to 28.1 C. Assume ideal behavior. What is the change in ...
by Charlene Tang 1B
Mon Jan 25, 2016 10:41 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: ∆U in Isothermal Reversible Expansion
Replies: 2
Views: 406

∆U in Isothermal Reversible Expansion

Why is ∆U zero in isothermal reversible expansion?
by Charlene Tang 1B
Wed Jan 20, 2016 9:59 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Calculating Enthalpy Density for a Reaction
Replies: 1
Views: 1905

Calculating Enthalpy Density for a Reaction

This is #51 on the homework. The enthalpy of formation of trinitrotoluene (TNT) is 67 kJ/mol and the density of TNT is 1.65 g/cm^3. Explore its potential as a rocket fuel by calculating its enthalpy density (enthalpy released per liter) for the reaction: 4C 7 H 5 N 3 O 6 + 21O 2 --> 28CO 2 + 10H 2 O...
by Charlene Tang 1B
Fri Jan 15, 2016 5:31 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Clairifcation on when to use entropy equations.
Replies: 3
Views: 738

Re: Clairifcation on when to use entropy equations.

Ok I'll try to tackle these one at a time. Change in entropy = Boltzmann's Constant * ln (w2/w1) ^ Because entropy by itself is S=(kB)*ln(W), ∆S will be (kB)*ln(W2) - (kB)*ln(W1). Which can be simplified, using log rules, to ∆S=(kB)*ln(W2/W1) <-- this calculates the change in entropy per particle Si...
by Charlene Tang 1B
Fri Jan 08, 2016 11:35 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: heat and state function
Replies: 2
Views: 388

Re: heat and state function

Heat is not a state function because it depends on the pressure during heating/cooling and not just the initial and final temperatures and pressure, while enthalpy is measured at constant pressure. State functions are step independent functions and only the initial and the final values matter, not t...
by Charlene Tang 1B
Wed Dec 02, 2015 12:05 am
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Weak Acids Acting As Strong Acids
Replies: 1
Views: 458

Weak Acids Acting As Strong Acids

Acetic acid is used as a solvent for some reactions between acids and bases.
a) Nitrous acid and carbonic acid are both weak acids in water. Will either of them act as a strong acid in acetic acids?
b) Will ammonia act as a strong or weak base in acetic acid?
by Charlene Tang 1B
Fri Nov 20, 2015 10:06 am
Forum: Ideal Gases
Topic: How Density is Affected
Replies: 1
Views: 359

How Density is Affected

How does change in pressure and temperature affect density?
by Charlene Tang 1B
Thu Nov 12, 2015 5:27 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: How Pressure Affect Reactions
Replies: 1
Views: 386

How Pressure Affect Reactions

In class, Dr. Lavelle said that the shifting of reactions doesn't necessarily depend on whether one side has more moles of gas than the other. Why doesn't adding a nonreactive gas (like He) and increasing the pressure affect the shifting of reactions?
by Charlene Tang 1B
Tue Nov 10, 2015 9:09 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydentate and Oxidation Numbers
Replies: 4
Views: 887

Polydentate and Oxidation Numbers

How do you determine if a ligand can be polydentate and the maximum number of places on the ligand that can bind simultaneously to a single metal center? For instance, why is HN(CH2CH2NH2)2 tridentate? How would polydentate ligands affect the oxidation number of the coordination compound? For exampl...
by Charlene Tang 1B
Fri Nov 06, 2015 10:11 am
Forum: Dipole Moments
Topic: Polarity of XeF2
Replies: 4
Views: 12617

Polarity of XeF2

Why is XeF2 non polar? Doesn't it have lone pairs?
by Charlene Tang 1B
Fri Oct 30, 2015 10:40 am
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bond Order and Bond Stability
Replies: 4
Views: 5870

Bond Order and Bond Stability

Does a higher bond order mean that the molecule is more stable?
by Charlene Tang 1B
Fri Oct 23, 2015 1:27 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR - T-shaped Molecules and Bond Angles
Replies: 1
Views: 583

VSEPR - T-shaped Molecules and Bond Angles

1. According to the book, molecules that are AX3E2 are T-shaped. The illustration of the molecule shows that the lone pairs replace 2 of what would be the equatorial atoms, which would make them 120 degrees from each other. Since there is electron repulsion, why don't the lone pairs replace the top ...
by Charlene Tang 1B
Thu Oct 22, 2015 12:27 am
Forum: Octet Exceptions
Topic: Chapter 3 Question 111 + Radicals
Replies: 1
Views: 364

Chapter 3 Question 111 + Radicals

111. A common biologically active radical is the pentadienyl radical, RCHCHCHCHCHR', where the carbons form a long chain, with R and R', which can be a number of different organic groups, at each end. Draw three resonance structures for this compound that maintain carbon's valence of 4. I was just w...
by Charlene Tang 1B
Wed Oct 21, 2015 11:13 pm
Forum: Resonance Structures
Topic: Chapter 3 Question 99
Replies: 1
Views: 375

Chapter 3 Question 99

The question asks us to draw the most important Lewis structure for the N 5 + ion, including all equivalent resonance structures. How come the most important Lewis structures, according to the solution manual, have no two like formal charges near one another? Why can't we have 3 identical formal cha...
by Charlene Tang 1B
Mon Oct 19, 2015 3:14 am
Forum: Lewis Structures
Topic: Lewis structure for glycine
Replies: 2
Views: 1356

Lewis structure for glycine

For the Lewis structure for glycine (H2C(NH2)COOH), does the 2 oxygens have to bond with the same carbon like it did in the answer key? Or does it not matter as long as we have 30 electrons?
by Charlene Tang 1B
Fri Oct 16, 2015 10:23 am
Forum: Trends in The Periodic Table
Topic: group 15 electron affinity
Replies: 1
Views: 814

Re: group 15 electron affinity

The p orbitals can fit a total of 6 electrons in its 3 orbitals. Elements in group 15 have 1 electron in each of the 3 orbitals, so it makes sense that it'll take more energy than expected to add another electron to the same orbital because of electron-electron repulsion.

Hope that makes sense!
by Charlene Tang 1B
Sun Oct 11, 2015 4:52 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Question 1.57 - Different Series
Replies: 1
Views: 427

Question 1.57 - Different Series

Lines in the Balmer series of the hydrogen spectrum observed at 656.3, 486.1, 434.0, and 410.2 nm. What is the wavelength of the next line of series? I'm just unsure as to how to approach this question. Does Balmer series mean that the electron always return to n=2? Or can it be n=3 or other numbers...
by Charlene Tang 1B
Sun Oct 04, 2015 10:08 pm
Forum: Limiting Reactant Calculations
Topic: 2 Questions from M. Limiting Reactants
Replies: 5
Views: 3040

Re: 2 Questions from M. Limiting Reactants

Oh my goodness thank you so much!
That must have taken quite a while to write.

And Alina I think you do that when you're given mass percentages or have calculated them so you can carry out the rest of your calculations easier.
by Charlene Tang 1B
Fri Oct 02, 2015 12:03 am
Forum: Limiting Reactant Calculations
Topic: 2 Questions from M. Limiting Reactants
Replies: 5
Views: 3040

2 Questions from M. Limiting Reactants

1. A compound found in the nucleus of a human cell was found to be composed of carbon, hydrogen, oxygen, and nitrogen. A combustion analysis of 1.35g of the compound produced 2.20g of CO2 and 0.901g of H2O. When a separate 0.500g sample of the compound was analyzed for nitrogen, 0.130g of N2 was pro...

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