Search found 21 matches

by Xinyi_Yan_3L
Sat Mar 18, 2017 9:29 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019097

Re: Post All Chemistry Jokes Here

"This is a favored process, but with a high energy barrier."
chem joke.jpg
by Xinyi_Yan_3L
Sun Mar 12, 2017 1:52 pm
Forum: *Alcohols
Topic: Determining phenol functional groups
Replies: 3
Views: 891

Re: Determining phenol functional groups

I also don't think so. Alcohol functional group is a hydroxyl group that attaches to a saturated carbon. However, because the OH of phenol functional group is attached to a benzene ring, the hydroxyl group of phenol attaches to an unsaturated carbon. Therefore the phenol functional group is differen...
by Xinyi_Yan_3L
Sun Mar 05, 2017 11:58 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Ratio of Rate Constants (Energy Barriers)
Replies: 2
Views: 339

Re: Ratio of Rate Constants (Energy Barriers)

This can be explained with the Arrhenius equation: k=A*Exp(-EA/(R*T)), which is determined through experiments. A higher energy level means reactants must collide with higher energy, which is harder to achieve. Therefore the rate is lower and the rate constant is smaller.
by Xinyi_Yan_3L
Sun Feb 26, 2017 10:08 pm
Forum: General Science Questions
Topic: Gases in Atmosphere
Replies: 1
Views: 320

Re: Gases in Atmosphere

Because ozone is constantly produced in the upper atmosphere, where there is intense ultraviolet light. UV light has shortwave length and high frequency(higher energy), and can break O2 into two oxygen atoms. The single oxygen atom combines with O2 to form O3. So even though ozone tends to sink or b...
by Xinyi_Yan_3L
Sun Feb 19, 2017 10:02 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019097

Re: Post All Chemistry Jokes Here

IMG_1909.JPG
by Xinyi_Yan_3L
Sun Feb 12, 2017 5:21 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Practice Midterm Winter 2013: Q5B
Replies: 3
Views: 401

Re: Practice Midterm Winter 2013: Q5B

I think here "configuration" infers electron configuration rather than geometry orientation. Clearly F has a more complex electron configuration than H. A more complex electron configuration means more possible microstates. Therefore the more F the molecule has, the larger the molar entropy.
by Xinyi_Yan_3L
Sun Jan 29, 2017 10:25 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Quiz question #7
Replies: 1
Views: 278

Re: Quiz question #7

Actually this process leads to an decrease in entropy. For an isothermal process, ΔG=q(reversible)/T
Clearly, since the system (the glass of water) is losing heat, q is negative Thus ΔG is also negative, which means decrease in entropy.
by Xinyi_Yan_3L
Sun Jan 22, 2017 3:55 pm
Forum: Calculating Work of Expansion
Topic: Example of reversible expansion?
Replies: 1
Views: 268

Example of reversible expansion?

For irreversible expansions, an example would be a piston with atmosphere as external environment. But can some one give me a real-life situation as an example of a reversible expansion, if there's any? I understand in reversible expansion process, the pressures of the system and exterior are always...
by Xinyi_Yan_3L
Sat Jan 14, 2017 9:38 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Using Reaction Enthalpies
Replies: 1
Views: 229

Re: Using Reaction Enthalpies

You can decide which method to use by looking at what information you are given in the question. When you know the reaction enthalpies of reactions related to your given reactions, you use Hess's law. For example, if you are given N2+ O2= 2NO ΔH1°=180.5 kJ and N2+2O2=2NO2 ΔH2°=66.4 kJ, and want to ...
by Xinyi_Yan_3L
Sat Dec 03, 2016 10:16 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Why aqua is monodentate?
Replies: 2
Views: 369

Re: Why aqua is monodentate?

Thanks so much!
by Xinyi_Yan_3L
Fri Dec 02, 2016 10:02 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Why aqua is monodentate?
Replies: 2
Views: 369

Why aqua is monodentate?

According to its Lewis structure, aqua(H2O) has two lone pairs. This means that aqua can possibly bind to two molecules, right? But why it is monodentate?
by Xinyi_Yan_3L
Tue Nov 29, 2016 6:02 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Calculating Bond Order
Replies: 2
Views: 1540

Re: Calculating Bond Order

Basically you can calculate the bond order by counting the bonds, with the help of the lewis structure. For example, O2 has a double bond and has a bond order of 2. If we draw the lewis structure for NO3-, we may find out that it's a resonance structure with one double bond and two single bonds. So ...
by Xinyi_Yan_3L
Sun Nov 27, 2016 5:39 pm
Forum: Calculating the pH of Salt Solutions
Topic: classifying acidity/basicity of NaClO
Replies: 1
Views: 364

Re: classifying acidity/basicity of NaClO

Na is not an acidic cation not because of its charge, but because NaOH is a strong acid and ionizes completely in water. So yes, ClO is the only ion reacting with water and the determining the pH. And NaClO is basic and your reason is correct For AlClO3, I think we need the specific ka and kb of Al ...
by Xinyi_Yan_3L
Fri Nov 18, 2016 7:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Chapter 11 Q 89
Replies: 3
Views: 467

Re: Chapter 11 Q 89

So according to the graph, Change in A=ΔA=27.5-27.5=-10 (approximately), ΔB=5, ΔC=10 ΔA: ΔB: ΔC=2:1:2, which means for every two unit's of decrease in A's PP, there is one unit of increase in C's PP and two in D's. So the coefficient of A, B, and C is 2: 1: 2 And the equation will be: 2A --> B + 2C ...
by Xinyi_Yan_3L
Fri Nov 11, 2016 12:42 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Chapter 11 Question 43
Replies: 2
Views: 376

Re: Chapter 11 Question 43

As initially the concentration for N2 is 0 and equilibrium concentration is x, the change in N2 concentration is x. The change in NO concentration is -2x, twice the change in N2 concentration. Given NO' s initial concentration (1.0) and change in concentration (-2x), we can know that the equilibrium...
by Xinyi_Yan_3L
Fri Nov 04, 2016 7:03 pm
Forum: Hybridization
Topic: Homework 4.43
Replies: 1
Views: 234

Re: Homework 4.43

I don't know the exact reason, but we can make generalization by comparing sp3 and sp2 orbitals. The sp2 orbitals has less p-character and more s-character than sp3 (you may think of sp2 has 1/3 s, while sp3 has 1/4 s), and has lager bond angles. Generally, the more s-character the hybrid orbital ha...
by Xinyi_Yan_3L
Sat Oct 29, 2016 10:01 am
Forum: Hybridization
Topic: 25.d
Replies: 2
Views: 302

Re: 25.d

After sulfur forms bonds with each of the fluorine, it still has a lone pair left. The side with the lone pair has a slightly negative charge, thee other side has a slightly positive charge. So SF4 is polar.
by Xinyi_Yan_3L
Thu Oct 20, 2016 5:41 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7606
Views: 1019097

Re: Post All Chemistry Jokes Here

IMG_2037.jpg
I saw this on Facebook. It's so funny.
by Xinyi_Yan_3L
Sat Oct 15, 2016 3:38 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s orbitals
Replies: 2
Views: 645

3d and 4s orbitals

I learnt in class that 3d orbital has lower energy level than the 4s orbital. Then why electrons first fill in 4s orbitals before they go to 3d?
by Xinyi_Yan_3L
Sat Oct 08, 2016 10:50 pm
Forum: Properties of Electrons
Topic: Kinetic Energy of Electrons to moles? [ENDORSED]
Replies: 1
Views: 372

Re: Kinetic Energy of Electrons to moles? [ENDORSED]

To know the kinetic energy of the electrons, you need to know both their mass and velocity. According to the formula: E(k)=(1/2)m*v^2 The mass of one mole of electrons is 9.1*10^-31kg * 6.02*10^23/mol(Avogadro's number) * 1mol. And the unit of v^2 is (m/s)^2, the unit of the final answer is: kg*m^2/...
by Xinyi_Yan_3L
Sun Oct 02, 2016 8:25 pm
Forum: Properties of Light
Topic: 1.57 : Wavelength of next line in series ?
Replies: 1
Views: 473

Re: 1.57 : Wavelength of next line in series ?

397.0nm The next wavelength is the fifth in balmer series and is for light emitted when electron transits from n=7 to n=2 by definition. First calculate the energy difference between n=7 and n=2 using the equation: ΔE=E2-E7=-hR/4-(-hr/49)=-5.008*10^(-19)J ΔE is negative because energy is emitted as ...

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