CHEMISTRY COMMUNITY

Siddiq 1E

the rate law tells you the overall rate of the reaction in terms of its reactants, this will include K. the rate order depends on the exponent on each reactant, which indicates the number of molecules of that substance that needs to collide. Molecularity refers to the number of species in an elemen...

Siddiq 1E

Can someone explain the relationship between rate law, order, and molecularity?

Siddiq 1E

If you have an equation that is A + A --> B, does that necessarily mean the rate law will be k=[A]^2?
Like does molecularity define the rate law?

Siddiq 1E

How are non-elementary steps and elementary steps related?

Siddiq 1E

Usually the left most species are in the anode reaction and right most in the cathode.

Siddiq 1E

josmit_1D wrote:why are third order reactions and higher less frequent?

The probability that three reactants will simultaneously collide with enough energy and the correct orientation is low.

Siddiq 1E

Can someone do a detailed walkthrough of how to do this problem? I keep getting the wrong answer :( 7A.13) In the reaction CH Br(aq) 1 OH2(aq) S CH OH(aq) 1 33 Br2(aq), when the OH2 concentration alone was doubled, the rate doubled; when the CH3Br concentration alone was increased by a factor of 1....

Siddiq 1E

Hi, I'm just really confused about what reaction mechanisms are and why they are relevant?

Siddiq 1E

Can someone do an overview about the relationship between elementary reactions, rate determining reactions, slow steps, and rate constants and orders?

Siddiq 1E

Does someone have a good example from the book or something that asks about determining the rate-determining (slow) step?

Siddiq 1E

How does the Nernst equation change based on if you use K or Q?

Siddiq 1E

^^^^ same question, isn't it the same delta G?

Siddiq 1E

For this particular problem protonated is just a descriptor of the substance that remains. you can tell that the drug will remain in its protonated form because K is smaller than 1, which means the denominator has a higher concentration, which is the protonated form of the drug.

Siddiq 1E

Hi, I'm a little confused about the relationship between stoichiometric coefficients and rate laws/constants?

Siddiq 1E

Hi, I had a question about 6A on the midterm: Hydrochloric acid is a naturally-occurring component of the gastric acid produced in the digestive systems of most animal species, including humans. Consider this equation for the formation of HCl: 2H2(g) + 2Cl2(g) → 4 HCl(g) ∆Ho = –92.3 kJ Which stateme...

Siddiq 1E

I was looking at the graphs for endothermic and exothermic reactions and I wanted clarification about whether in an endothermic reaction, the amount of activation energy includes the amount of energy that is absorbed in the reaction?

Siddiq 1E

If you're given a chart, you can tell because exothermic reactions have energy released and therefore reactants are higher than products. In an endothermic reaction, energy is absorbed and products are higher than reactants.

Siddiq 1E

I'm a little confused about the meaning of delta s total versus delta s of the system/surroundings.

Siddiq 1E

Does expansion cause an increase or decrease in work? And why?

Siddiq 1E

Can someone explain this question from the midterm? Which combination of solutions of HCl and NaOH would produce the largest ∆T? Ans _____B (A) 50 mL of 1 M HCl with 50 mL of 1 M NaOH (B) 50 mL of 2 M HCl with 50 mL of 2 M NaOH (C) 100 mL of 1 M HCl with 50 mL of 2 M NaOH (D) 100 mL of 1 M HCl with ...

Siddiq 1E

Sorry I meant a pressure change for one of the reactants or products.

Siddiq 1E

If you are given an equation whose reactants and products are all in gaseous phases, and also given their molar concentrations, how do you calculate K?

Siddiq 1E

Can someone explain the relationship between pressure, volume, and le chatelier? Like what if both sides of the equation have equal numbers of moles, how will a pressure change affect that?

Siddiq 1E

Would we ever have to come up with reaction mechanisms or steps? Or just interpret them?

Siddiq 1E

does this mean molecularity corresponds with rate order?

Siddiq 1E

When is molecularity relevant?

Siddiq 1E

Hi, I'm just a little confused about how you can tell the differences between reaction mechanisms and when that is relevant?

Siddiq 1E

Hi, I was working on HW question 7A.7 and it made me realize I don't really understand what it means if a reaction is first order? I know how to tell based on the graph etc, but what does it mean in terms of units and reaction speed etc?

Siddiq 1E

How do you know when to include platinum in the cell diagram?

Siddiq 1E

Hi, for 6.57 can someone explain why K is equal to Ka squared? Like why do you need to take the radical of K at the end to get Ka?

Siddiq 1E

For 6N 17, I was wondering how you can tell the cell can do work? Is it because delta G and wmax are negative? for example, if you had gotten a positive value for delta G would the answer be that the cell cannot do work?

Siddiq 1E

Hi, how is the strength of reducing agents determined?

Siddiq 1E

Hi, can anyone explain the relationship between work and cell potential, and free energy and cell potential?

Siddiq 1E

Hi, i'm a little confused as to how in 6N. 15 you know that the concentration of nickel ions is less in the half cell with hydroxide ion than the other cell?

Siddiq 1E

Hi, for the question 6N.9, I don't understand why you can assume the tin electrode is the anode?

Siddiq 1E

Siddiq 1E wrote:Thanks everyone but I actually need help writing it from the cell. I know what oxidation and reduction mean i just can't seem to discern which is which from the cell

For example, 6L. 3 gives just the elements.

Siddiq 1E

Thanks everyone but I actually need help writing it from the cell. I know what oxidation and reduction mean i just can't seem to discern which is which from the cell

Siddiq 1E

Hi, for the 6L problems that ask you to write the half reactions, how do you know which is being oxidized and which reduced?

Siddiq 1E

Hi, I'm a little confused about the 6L problems that ask you to write the half reactions --> how do you know which half reaction is the cathode and which is for the anode?

Siddiq 1E

Can someone explain the relationship between maximum potential difference and voltage?

Siddiq 1E

Hi, I'm not quite understanding how the flow of the cell works -- if electrons are travelling toward the cathode, how can cations also be travelling toward the cathode? Shouldn't it be that anions flow toward the cathode?

Siddiq 1E

You have to read the conditions of the question to be able to tell if it is open, closed, or isolated. Evaluate what is allowed to be exchanged with the surroundings. Can energy be exchanged, but matter cannot? This would be a closed system. Hope this helped! Thanks! Still a little confused... how ...

Siddiq 1E

Can anyone tell me how to differentiate between open, closed, and isolated systems? Like how could you tell in the question which type of system it is?

Siddiq 1E

I'm a little confused as to why for 4.5 in the hw 10 hours is divided by 0.5 hours?

Siddiq 1E

Can anyone explain where the delta n = 2 and delta n =1/2 comes from in the solution to number 7 of pizza rolls?

Siddiq 1E

Can someone explain when the boltzmann equation is more useful than the other methods to calculate entropy?

Siddiq 1E

Hi, for the answer for 6B3, i was confused as to why on part A, the solutions manual did not convert 0.025 to moles per 250 milliliters?

Siddiq 1E

So I understand the basic set up of the question, but I am confused on the answer for D. To me it seems like there's more moles on the left side so the reaction would favor the products?? I'm also confused about B :(

Siddiq 1E

Since there are 5 valence electrons, when you hybridize the orbitals to get sp3, there will be one valence with a lone pair and three orbitals with one electron in it (that's the five valence electrons you're asking about). I hope this answers your question! :) It does thank you so much!! Does this...

Siddiq 1E

Perhaps I wasn't clear. I know why it has sp3 hybridized orbitals but my question has to do with the amount of electrons in the sp3 orbital.

Siddiq 1E

So I know electrons prefer to occupy unhybridized orbitals rather than spin pair in a hybridized orbital, so I'm confused as to why NH3 is hybridized sp3 when it has 5 electrons? It has a lone pair but I don't understand how that plays into it.

Siddiq 1E

when you write hybridized orbitals out, like when you're labelling atoms in a molecule, do you include a "2p" for example, if there's a pi bond? For example NO2, when you write the hybridized orbitals for nitrogen, do you put sp2 2p or just sp2? And do you include the energy level, 2?

Siddiq 1E

How can you tell how to classify ligands as mono, bi, tri, dentate?

Siddiq 1E

Wait if it's an acidic oxide why is the answer basic...? Am i missing something or getting caught up in the wordiness?

Siddiq 1E

What are examples of amphoteric oxides, and what should we know about them?

Siddiq 1E

I'm a little bit confused as to how the structure of cisplatin allows it to act as a chemotherapeutic agent.

Siddiq 1E

When does light act as a wave?

Siddiq 1E

Thank you all for the replies -- I get why it goes across now, but I still don't understand why it goes straight up?

Siddiq 1E

We talked about Lewis acids and bases mostly in the context of coordination compounds, so I'll explain it in that context too. In a coordination compound, the Lewis acid (electron pair acceptor) is the positively charged transition metal. Notice that even though it is positively charged, !! it does...

Siddiq 1E

I'm confused about how lewis acids accept electrons? And how do lewis bases donate electron pairs? I get Bronsted acids and bases do proton accepting/donating through Hydrogens but I don't know how lewis acids/bases work. Thanks in advance :)

Siddiq 1E

Ahhh I understand now!! Thank you everyone :)

Siddiq 1E

Same as above!! Does that mean we can determine hybridization in every molecule??

Siddiq 1E

Hi I'm having trouble still picturing the shapes in 3D, which is problematic because that has a lot to do with polarity of a molecule. Does anyone have any advice on how to solve this? I know mostly you have to determine polarity on a case by case basis but is there any way to have a key like this s...

Siddiq 1E

Thanks everyone. The other thing that's confusing to me is how does an atom donate a proton? I thought interactions between atoms were all through electrons.

Siddiq 1E

Hi, I still don't understand why the correct answer for the graph on the midterm isn't just linear.

Siddiq 1E

Hi, how can we determine the number of hydrogen bonding sites between two molecules?

Siddiq 1E

Hi, I'm a little confused about the difference between bronsted and lewis acid/bases. I know the definitions but I'm wondering practically is there a difference? Is one a more correct depiction of acids and bases than the other? Thanks in advance.

Siddiq 1E

I think that in these cases the octet rule isn't so strictly enforced.

Siddiq 1E

Dissociation energy will be larger(stronger) for a stronger bond.

Siddiq 1E

How do we determine ionic or covalent character of bonds? Is it just electronegativity?

Siddiq 1E

All IMF's contribute to boiling points. Stronger IMF's will result in higher boiling points.

Siddiq 1E

I have the same problem... I usually draw it out but if it's too complicated I don't know what to do :(

Siddiq 1E

I could be wrong but I interpreted this to mean that when atoms with similar atomic radii are bonded to the same atom they will have the same bond strength

Siddiq 1E

How can we calculate dissociation energy? Will we need to?

Siddiq 1E

I don't know if it necessarily has to do with which is more or less polar, but I think it has to do with the direction and cancellation of dipoles. There will be a stronger dipole moment in the structure where dipoles are in the same direction.

Siddiq 1E

Will we need to draw dipole moments on the exam?

Siddiq 1E

I think it would be helpful to know generally which type of bond creates higher or lower boiling/melting points.

Siddiq 1E

Atoms with higher electronegativity tend not to be central atoms. They are on the outside so they have more electrons to themselves

Siddiq 1E

I think it is elements that have electrons in 2p state or higher.

Siddiq 1E

I think N,O, and F are the strongest hydrogen bonds so they are specially named as such. Hydrogen can have IMF with other elements but these forces are not as strong.

Siddiq 1E

Yes! The equation E=hv can be applied because it corresponds to the energy of one photon. The de Broglie equation is used for the energy of one particle/atom.

Siddiq 1E

Past the 2p level, atoms can contain more electrons.

Siddiq 1E

Looking at the formal charge and electronegativity, oxygen would rather have a negative formal charge than nitrogen because oxygen is more electronegative.

Siddiq 1E

After the 4s orbital is occupied AND electrons enter the 3d state, THEN the 3d state is lower in energy than 4s, so it would be written first.

Siddiq 1E

For resonance, if it asks whether the hybrid structure is equally inclusive of all the possible resonance structures, it's an equal structure if all the formal charges in every structure are equal. If the formal charges are different, the structure with the most favorable charge will most influence ...

Siddiq 1E

In this case I think the 3d shell is lower in energy than the 4s shell.

Siddiq 1E

So the number of unpaired electrons just means the number of valence electrons. You can draw a lewis dot structure to visualize this

Siddiq 1E

Is it just using the known valence electrons for Oxygen and Chlorine and subtracting those values from the total electrons? Thanks in advance!

Siddiq 1E

So for this problem, we know the other elements are Oxygen and Chlorine, so which electrons do we count for the central atom?

Siddiq 1E

Doesn't nuclear charge decrease down a group? I'm confused as to why the trend doesn't follow the ionization energy trend exactly.

Siddiq 1E

What is the relationship between effective nuclear charge and ionization energy?

Siddiq 1E

For the photoelectric effect, will the calculations only involve kinetic energy?

Siddiq 1E

So for these we would have to just memorize the exceptions to the rules, correct?

Siddiq 1E

Will the lowest energy level always correspond to quote unquote "where the electron ends up" ? What if the electron jumps up energy levels?

Siddiq 1E

For E=hv, this equation gives the energy of one photon. Every time you use this equation, the energy given is per photon.

Siddiq 1E

So I figured this out regarding D11: I think of orbitals as the spots for the electrons. So the s orbital has one spot (fitting two electrons with different spins), the p orbital has 3 spots (6 electrons), d has 5 spots, and f has 7. The subshells are each letter themselves. Hope this helps!

Siddiq 1E

Frequency is measured in Hertz, and wavelength is measured in meters.

Siddiq 1E

What I've been doing so far is doing all (most? some? (; ) of the homework problems and then copying 5 to give the TA. I don't think more counts as EC. If you have questions on the others, though, I'd definitely ask your TA or someone at peer learning sessions.

Siddiq 1E

The one to one relationship between photons and electrons accounts for this. By looking at the equation we can determine that a shorter wavelength means higher frequency and thus more energy per photon, allowing it to eject one electron. It doesn't matter if the overall energy is more; if the energy...

Siddiq 1E

For me it helps to write notes on the side of how much of each atom you have. This helps me keep track of each atom number and reduces confusion. If I am really confused and feeling lost I start from the beginning again and often I've missed a small detail. Honestly the best thing to do is just prac...

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