CHEMISTRY COMMUNITY

Tara_Shooshani_3N

Since U=0, w=-q

Tara_Shooshani_3N

There is a cis to indicate the placement of the substituents on the chair structure. The cis means that the methyl is axial and the isopropyl is equatorial (or vice-versa).

Tara_Shooshani_3N

Why do aromatics belong in the nuthouse?

Because they’re all CYCLO.

Tara_Shooshani_3N

For chapter 1 Qs 16 and 17, why are the molecules named:
2-isopropyl-1,1-dimethylcyclopentane in instead of 1,1-dimethyl-2-isopropylcyclopentane
and
4-tertbutyl-1,2-dimethylcyclohexane instead of 1,2-dimethyl-4-tertbutylcyclohexane ?

Thanks!

Tara_Shooshani_3N

Yes, it appears as if they are ¯\_(ツ)_/¯ Both 2-pentene molecules.

Tara_Shooshani_3N

Based on what I've seen in examples, as long as you label each step and section of the graph, you can make the graph as high/low/wide as you want. Obviously, you need to have every segment of the graph line up with the right step of the reaction and have them proportional to each other. Hope that he...

Tara_Shooshani_3N

An intermediate is a molecule that is produced from the reactants in the early steps of a mechanism, but is not present in the final molecular formula of the chemical reaction. When you add the mechanism formulas together to get the simplified chemical formula, the intermediates will always cancel.

Tara_Shooshani_3N

It's negative when you're finding the concentration of a reactant, which is decreasing. It's positive when finding the concentration of the products, which is increasing.

Tara_Shooshani_3N

Can the following equations be used interchangeably to find K?:

deltaG = -RTlnK
deltaEcell = ((RT)/(nF))lnk = (.0257/n)lnK

Thank you!

Tara_Shooshani_3N

In the equation E=E - (RT)/(nF) * ln(Q), how do we know which molecules are the products and which are the reactants to plug in for Q? Is it always the cathode, or always the anode, or based off something else entirely?

Thanks

Tara_Shooshani_3N

Entropy (S) is a measurement of disorder and randomness, while enthalpy (H) is the amount of heat a reaction releases or absorbs. Each question will probably specify whether to use entropy or enthalpy, or you can tell from the information the question provides.

Tara_Shooshani_3N

For #8, I don't understand why the reaction will not be spontaneous at any temperature.

Please help! Thanks!

Tara_Shooshani_3N

Is high entropy more stable than low entropy?

For example, which is more stable: a system with entropy 10 or entropy 20?

Tara_Shooshani_3N

In the equation relating degeneracy and entropy, S = kB * ln(W), where do we get the value for kB (k-sub-B)?

Tara_Shooshani_3N

It depends on the elements being used, but in general, you subtract the mean bond enthalpy of the double bond you are forming from the single bond you are breaking. For example, if we take a single bonded C-C and convert it to a C=C bond, we first have to add energy to break the single bond, and the...

Tara_Shooshani_3N

Heat is an extensive property because it changes when the size of the sample changes. Somethkng that has mass 10 grams will not have the same temperature as something with mass 100 grams.

Tara_Shooshani_3N

I don't think that strong and weak acids and bases are determined based on a set number on the pH scale because temperature and solvent change pH. Instead, a strong acid/base is one that completely ionizes in a reaction. A weak acid/base does not completely ionize. You can tell in a question whether...

Tara_Shooshani_3N

One of the roots will be larger than one or both of your concentrations, so when you try subtracting it from your concentration you will get a negative new concentration, which does not make sense. So use the other value that results in two positive concentrations.

Tara_Shooshani_3N

During the analysis of an unknown acid HA, a 0.010 m solution of the sodium salt of the acid was found to have a pH of 10.35. Use Table 12.1 to write the formula of the acid.

I don't clearly understand the answer key, please help.

Thanks!!

Tara_Shooshani_3N

The question reads: Complete the overall equation, and write the complete ionic equation and the net ionic equation for each of the following acid-base reactions. HF (plus) NaOH = LiOH (plus) HI = I understand how to write the overall equations, but I am confused on how to write the complete ionic a...

Tara_Shooshani_3N

This is a question from the first equilibrium module: For a chemical reaction that has reached equilibrium which statement is false ? a) the forward reaction rate is the same as the reverse reaction rate b) no matter what combination of concentrations of reactants and products we start with the reac...

Tara_Shooshani_3N

A ligand is a molecule or ion that bonds with a metal atom. What we're focusing on is ligands bonding to central transition metals to form coordination compounds. The transition metal itself is typically not the ligand.

Tara_Shooshani_3N

When writing the formula for potassium tetracyanonickelate (II), why is the answer K2[Ni(CN)4] and not just K[Ni(CN)4]?

Thanks.

Tara_Shooshani_3N

Are trigonal pyramidal and pyramidal the same thing? What are the bond angles?

Thanks.

Tara_Shooshani_3N

H, He, Li, and Be are exceptions since they cannot hold 8 electrons. As for elements that have expanded octets, most of the elements after Si have expanded octets since they're in the third energy level (third row of the periodic table) and have empty d orbitals. I've specifically seen a lot of P an...

Tara_Shooshani_3N

I'll go part by part to explain where the numbers come from: a) when l=1, we know it is a p-orbital, and 6 electrons can fit in a p-orbital, so the answer is 6. b) and d) in any m group there are always only 2 electrons maximum. One has upward spin, one has downward. c) when n=2, l can be either 0 o...

Tara_Shooshani_3N

You do not need to convert the units. Another way to write Hz is s^-1, so the seconds cancel and you're left with J. The book tends to use s^-1 instead of Hz when giving the units of frequency.

Tara_Shooshani_3N

To answer this you first need to convert the given energy from 348 kJ/mol to J/c-c bond. Basically, multiply by 1000J and divide by 6.022 * 10^23 c-c bonds to get 5.78 * 10^-19 J. Then substitute this energy value into the equation wavelength=hc/E. Your answer ends up being 344 nm, which is in the u...

Tara_Shooshani_3N

Can someone explain the series of conversions needed to use combustion analysis to find the empirical formula of a molecule given the mass of an unknown compound and the masses of carbon dioxide and water (and any other product) produced? I understand the concept of combustion analysis, but I always...

CHEMISTRY COMMUNITY

Search found 29 matches

Re: dU, q, w

Re: Q5B on 2008 Final

Re: Post All Chemistry Jokes Here

Order in naming [ENDORSED]

Re: 1.24

Re: Drawing Reaction Profiles

Re: intermediate

Re: homework 15.21 and 15.23

Methods of finding K

Plugging in #s for Q [ENDORSED]

Re: Entropy vs Enthalpy

Re: Quiz 1 Preparation Answers

Entropy and Stability

Degeneracy and Entropy

Re: Enthalpy [ENDORSED]

Re: Standard Enthalpy of Formation

Re: Identifying a strong acid

Re: Both Roots are positive

#12.75

Fundamental J.5

Reaction at equilibrium

Re: What is a Ligand?

Subscripts of atoms outside the brackets

Trigonal pyramidal vs. pyramidal

Re: Lewis Structure Octet Rule Exceptions

Re: Chapter 2 Question 29 [ENDORSED]

Re: Quiz 1 number 3

Re: C-C bond breakage by visible light? [ENDORSED]

Combustion Analysis