CHEMISTRY COMMUNITY

Yuchien Ma 2L

On the 2015 exam, Q10A did not list them as functional groups.
Since it says that any functional group that is incorrect will have points taken off, I was wondering if we needed to circle to double bonds as well since they are alkenes.

Yuchien Ma 2L

Are alkenes and alkynes considered functional groups?

Yuchien Ma 2L

So we don't ignore the prefix "iso"?

Yuchien Ma 2L

For #1.23 on the organic textbook, ( I can't write the question here because it is just diagrams)
Aren't the 2nd and 3rd molecule the same?

Yuchien Ma 2L

When do we use diene and triene in our names?
For example, for some problems the answer key would say 2-hexene, but other times it would say ...hept-1,4-diene.
Do we use only diene and triene for cyclic molecules or something else?

Yuchien Ma 2L

On #17 on the organic workbook, the answer key says "tetra-butane". But what is the difference between that and neobutane?

Yuchien Ma 2L

Why is methyl placed after isopropyl?

Yuchien Ma 2L

To remember the first four just use this:
Monkeys Eat Peanut Butter
It's a funny little sentence that helps you memorize it.
The rest of them are the same as normal prefixes

Yuchien Ma 2L

You ALWAYS use the slowest rate.

Yuchien Ma 2L

Is E a path function or state function?

Yuchien Ma 2L

You want the HIGHEST E cell, so it will always be the larger number minus the smaller number.
So whichever has a smaller E cell potential will always be reversed.

Yuchien Ma 2L

Use the least precise number in the question. You use the least precise number to decide how many sig figs to use.

Yuchien Ma 2L

I'm not sure what your first question means, but I'll go ahead and answer your second question. For electrochemistry, it is agreed that the oxidation state of O is -2, and H is usually +1 (although in some cases it can be -1), and we only know the charge of an element IF it is an ion, otherwise we w...

Yuchien Ma 2L

When delta G is negative, the reaction is favorable (spontaneous).
When delta G is positive, the reaction is unfavorable (non-spontaneous).
When delta G is equal to zero, the system is at equilibrium.

Yuchien Ma 2L

Calculate the reaction enthalpy: a) 3C262 (g) --> C6H6 (g) I drew the Lewis structure and added all the bond enthalpies, and then used the equation: E bonds broken - E bonds formed I found the reaction enthalpy to be -3409 kJ/ mol, while the solutions manual says -460 kJ/mol. I don't know really how...

Yuchien Ma 2L

You can opt to use the equation: E bonds broken - E bonds formed to solve this problem. The enthalpy of formation of C2H2 is -1300 kJ/mol, and H2= 286 kJ/mol, and C2H6 = -1560 kJ/mol. Using this equation, you end up with: Enthalpy of Formation of C2H6= (-1300 + 2(-286))- (-1560)= -312 kJ/mol I find ...

Yuchien Ma 2L

I have the same problem. Since density is g*cm^-3, I end up with an extra "g" unit that I cannot cancel out.
I don't really understand the solutions manual's way of explaining it.

Yuchien Ma 2L

Calculate the heat released by 5.025 g of K (g) at 0.400 atm as it cools from 97.6^o C to 25.0^o at (a) a constant pressure and (b) constant volume. Assume that krypton behaves as an ideal gas.

Can anyone explain how to solve this?
Thanks.

Yuchien Ma 2L

How do we compare the amount of work done? Do we just disregard the negative signs when comparing the amount of work done, or do we have to take in account the direction in which the work is done?
For instance, is -343 J of work considered more work than +120 J of work?

Yuchien Ma 2L

I personally found the chemistry community to be the most helpful out of all the resources available, because it is available 24/7 and you can post whenever and wherever. Whenever you have a question, you can always post it online, and then multiple people will answer your question through different...

Yuchien Ma 2L

Why is HClO 2 more acidic than HBrO 2 ? Isn't the H-Cl shorter and isn't Cl more electronegative than Br, so wouldn't HBrO 2 lose the H + proton more easily? The solutions manual says something about electronegativity making the H-O bond stronger, but is anyone able to explain that more clearly? Tha...

Yuchien Ma 2L

How do you exactly find out if the complex has an overall negative or positive charge? You can usually tell by the name. A negative coordination compound will have the suffix "-ate" in the name; positive ones will not. You can also add up all the charges of the central transition metal an...

Yuchien Ma 2L

I'm interested as well!

Yuchien Ma 2L

I have a question about H2O.
It has two valence electron lone pairs (4 valence electrons total), so why can't it make two polar coordinate bonds and be a bidentate ligand?
Why is it always a monodentate ligand?

Yuchien Ma 2L

For 17.31, part d, why is the aqua is written with the O backwards, like OH2, instead of H2O?
Also, how do we determine the order in which we put the ions when given the name of the coordinate compound?

Yuchien Ma 2L

I am completely confused about naming the coordinate compounds.
Do we need to know the latin names for all of the transition metals?
What is the order in which we put the different ligands before the ion?

Thanks in advance for your help.

Yuchien Ma 2L

We generally only use this when determining hybridizations.

Yuchien Ma 2L

Neutrons do have wave-like properties.

Yuchien Ma 2L

The higher the difference in electronegativity, the more ionic character a molecule has. That's because the higher the difference in electronegativity, the more unevenly the electrons would be shared between them.
Hope this helps!

Yuchien Ma 2L

Yes, the trends do not apply to the noble gases, and sometimes they go against the trends. For instance, the electron affinity of noble gases would be negative since they don't need that extra e-.
Hope this helps!

Yuchien Ma 2L

Electrons naturally repel each other, so they will fill up the empty orbitals before they fill up the already filled ones. Think of it like pairs of bus seats...you will sit in an empty pair of seats if you can. You will only sit with a stranger if there are no empty pairs of seats left, and you abs...

Yuchien Ma 2L

How many electrons can have the following quantum number:
a) n=2, l=1
b) n=4, l=2, ml=-1
c) n=2, l=1, ml= 0
d) n=7

I don't really even know how to start...please help!

Yuchien Ma 2L

Thank you so much for your help!
I have a much better understanding of the quantum numbers now.

Yuchien Ma 2L

Thanks, that really helped.
But what if n=6, and l is equal to 0,...n-1? What would l = 5 mean?

Yuchien Ma 2L

#2.21: What are the principal and orbital angular momentum quantum numbers for each of the following orbitals: a) 6p b) 3d c) 2p d) 5f i understand how to get the n (principal quantum number), it's the same as the energy level in front of the orbital. But I'm very confused about how to get the orbit...

Yuchien Ma 2L

Most periodic trends such as electronegativity and ionization energies goes up and right, only atomic radius is the exact opposite; it goes left and down. That's how I remember it.
Hope this helps!

Yuchien Ma 2L

Ionic bonds are much stronger than covalent bonds just because of the fact that the high difference between their electronegativity. An ionic compound is formed between nonmetals and metals, and a covalent compound is formed between two or more nonmetals. An easy way to remember is that you know met...

Yuchien Ma 2L

Electrons will always fill empty shells first (Hund's rule) so make sure that you draw out the electrons on all four sides before you start pairing them. For instance, carbon will have four valence electrons, one on each side, never two together on one side because electrons naturally repel each oth...

Yuchien Ma 2L

Thanks for the explanation!
It's so much clearer than the one in the solutions manual :D

Yuchien Ma 2L

A lamp rated at 32 W (1 W = 1 J * s^-1) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0s? How many moles of photons are emitted in that time interval? I got the first part, 32 J * s^-1 * 2.0 s = 64 J But I'm confused about the second part. I am...

Yuchien Ma 2L

Thanks a lot for the clarification!!
The second link really helped.

Yuchien Ma 2L

What is n1 and n2 in the Rydberg Equation?
Is n1 the initial energy level and n2 the final energy level?
If I do that then sometimes I'd end up with a negative frequency.

Thanks in advance

Yuchien Ma 2L

If my answer is 1.987*10^-3, and I need 2 sig figs, should I write my answer as 2*10^-3 or 2.0*10^-3?

Yuchien Ma 2L

Determine the mass of CuSO 4 • 5H 2 O that must be used to prepare 250 mL of 0.20 M CuSO 4 (aq). The solutions manual says 12 g which is what I got if I set up the equation as followed and solve for x: x grams * 1 mol/249.611 * 1 L/0.2 mol = 0.250 L But isn't CuSO 4 • 5H 2 O a hydrate? Therefore the...

Yuchien Ma 2L

I finally got it!
Thanks for your help

Yuchien Ma 2L

Using the formula M1V1=M2V2 I set up the following:

(0.159338 mols Na+/L) (V1) = (2.15*10^-3 mols Na+/L) (0.250 L)

and solving for V1 I got:
V1= 3.373 * 10^-3 liters, 3.373 mL, which is different from the solutions manual (which is 13.5 mL).

Please help!

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