CHEMISTRY COMMUNITY

Rian Montagh 2K

A catalyst is needed as a reactant in the first step while an intermediate is made in the first step (a product) and used as a reactant in the second step.

Rian Montagh 2K

Lasya Gudipudi 1A wrote:I am having the same issue too. Here is my work:

I did the problem the same way and got those answers as well.

Rian Montagh 2K

Why is the answer for 15.19 c 2.85 x 10^12? I keep on only getting 2.85. I thought about changing the units to mols but the answer key has the answer in mmols.

Rian Montagh 2K

When given two reduction half equations, how do you know which one to make the cathode and which to make the anode for calculating E naught of the overall reaction?

Rian Montagh 2K

I believe that you determine the slow step by seeing what that reaction rate depends on. The slow step is the step that determines what the rate of the reaction is. For example, in lecture one of the rates had [NO2]^2, so the slow step was the step where [NO2] reacted together, because that is the s...

Rian Montagh 2K

Can someone explain what exactly the order of a reaction means? I'm still confused about it.

Rian Montagh 2K

I think you can split them up in this case because HCl is a strong acid, meaning it fully dissociates into H+ and Cl-.

Rian Montagh 2K

Basically some Au+ will gain an e- (be reduced) to get to Au, and a different Au+ will lose 2e- (be oxidized) to get to Au3+.

Rian Montagh 2K

E naught is an intensive property and it's measured for substances with respect to a standard hydrogen electrode.

Rian Montagh 2K

Which of the following compounds become less stable with respect to the elements as the temperature is raised: (a) PCl5(g); (b) HCN(g); (c) NO(g); (d) SO2(g)? I was figuring this problem out using the delta H for the compounds and seeing that endothermic reactions have more stable products at higher...

Rian Montagh 2K

we also set delta G to 0 when we want to find the minimum temp to make a reaction spontaneous.

Also, a reaction at equilibrium does no work, so at delta G = 0 the reaction can do no work.

Rian Montagh 2K

I'm guessing it has to do with the fact that the definition of Gibbs free energy is the energy available to do work, which is probably hard to measure because it's not something you can measure like other forms of energy like heat.

Rian Montagh 2K

I think it has to do with the fact that no energy is transferred through a temp change or work of expansion to the surroundings. The only thing that changes is the volume of the system (free expansion = no work), and therefore the entropy increases with the volume increase.

Rian Montagh 2K

What is the difference between delta G and delta H if both of them are energy released from a reaction?

Rian Montagh 2K

Yes, calculate it for the 800 and 200 K system and surroundings using S = q/T and add them together.

Rian Montagh 2K

What do the different subscripts mean for the heat capacities, such as Cp and Cv?

Rian Montagh 2K

For b) the equation is w= -nRTln(Vf/Vi), and to find n you use PV=nRT and use the original given P value I believe (1.79 atm).

Rian Montagh 2K

The heat loss should be negative and the heat gained should be positive.

Rian Montagh 2K

Why are bond enthalpies averages from many different molecules?

Rian Montagh 2K

What is the difference between an extensive and intensive property? I know general heat capacity in extensive and specific heat capacity is intensive, but what do these words mean?

Rian Montagh 2K

I think one of the points of heat capacity is that you don't always want to know how much energy it takes to raise only one gram by one degree Celsius. Sometimes you have different amounts of a substance. I agree that specific heat capacity is more useful, but sometimes you might need to find out th...

Rian Montagh 2K

I think we've been using the Bronsted definition.

Rian Montagh 2K

To find the % ionization you use an ICE table to find the concentrations of the initial concentration of the unionized substance and the concentration of the ionized version of the substance at equilibrium. Then do [ionized]/[initial unionized] * 100. This is the percent. This relates to the 5% rule...

Rian Montagh 2K

Flask 3 represents equilibrium because from the third to the fourth flask there is no change in the number of products and reactants, meaning that equilibrium has been reached because a stable number of products and reactants is reached.

Rian Montagh 2K

I believe that Q would be calculated the same way as non acid and base reactions Q is calculated, and can be used in the same way to determine the direction of the reaction by comparing Q and K for the reaction at the specific temperature.

Rian Montagh 2K

I'm confused about how to convert between Kp and Kc and when you would need to do it?

Rian Montagh 2K

I'm still confused about this concept. For example, with the reaction CaCO3(s) <--> CaO(s) + CO2(g), how do the molar concentrations of the solids not change?

Rian Montagh 2K

The subtraction occurred on the ATP side because we were given the initial and final amounts of ATP, with the final amount being smaller than the initial amount. This means that 8.434x10^-3 was subtracted from the given initial amount to get to the given final amount. Since matter is conserved, all ...

Rian Montagh 2K

Jordan Lo 2A wrote:Do we need to memorize the formula in the book for converting between the 2?

My guess would be no, because we rarely if ever have to memorize any formulas.

Rian Montagh 2K

In the 6th edition number 11.9 asks for Kc for a reaction that involves gases. I thought you were suppose to always use Kp for gases, can someone explain why that's not the case?

Rian Montagh 2K

Elements in period three and above have expanded octets because they have access to the d orbitals for extra e- to go into.

Rian Montagh 2K

For test 3 number 3c., I was asked to write the hybridization a nitrogen atom that was bonded to a carbon and two hydrogens, and had a lone pair. I thought that it would have a tetrahedral formation with the four e- densities, so I labeled it sp3 and it was wrong. What's the correct hybridization an...

Rian Montagh 2K

In lecture for naming, chloride became chloro when naming a coordination compound, but in the book it says it should be chlorido. Am I missing something here?

Rian Montagh 2K

An example of a dipole would be H2O, where the difference in electronegativity causes a negative charge on the O and a positive charge on the H's. An induced dipole would be species that is usually non-polar but could have a high polarizability because it has many electrons. These electrons can be i...

Rian Montagh 2K

Yes they can because they have access to the d orbitals.

Rian Montagh 2K

Polarizability is how easily an atom or molecule can be polarized, and polarizing power is how well a species can polarize another species.

Rian Montagh 2K

No, I believe you have to look up the angles as there isn't a set amount to reduce the angle by. You just know it's slightly less.

Rian Montagh 2K

Why can atoms with sigma bonds rotate, but a pi bond will not allow it to rotate?

Rian Montagh 2K

Why does a long pair cause the bond angle to be slightly less than the atom without a lone pair?

Rian Montagh 2K

Also, a factor that plays into Van der Waals forces is the number of electrons. If there are many electrons, the interactions could be from the distorted electron clouds.

Rian Montagh 2K

I think polarizability can also apply to atoms and molecules, because their electron densities can change. The more electrons they have, the easier it is for their electrons to be distorted by an ion, for example.

Rian Montagh 2K

I wasn't sure about this either, but I googled it and I found that you are right. A single electron does repel count as an electron density, but with less strength of repulsion than a lone pair of electrons. The result is a larger bond angle as well because there is less repulsion, whereas a lone pa...

Rian Montagh 2K

Do you determine the central atom of a Lewis structure using least ionization energy or electronegativity? Or does it not matter?

Rian Montagh 2K

For me, I go by number of electrons, least electronegative at the center, and symmetry before I look at formal charge. Formal charge is the main criteria I use after getting the basic structure.

Rian Montagh 2K

Most atoms form an octet, H, He, and Be can have 2 valence, and elements in the 3rd period and up can have expanded octets into the d orbitals. B and Al sometimes only have 6 valence. Also, I believe that free radicals can mess up the octet rule. I am guessing that there are no atoms that MUST have ...

Rian Montagh 2K

I'm confused about this too but I believe in this case that since F is more electronegative, you could know that F would get the electrons.

Rian Montagh 2K

Is phosphorus more stable with 10 or 8 electrons?

Rian Montagh 2K

Why do only the s and p electrons count as valence electrons for most atoms?

Rian Montagh 2K

And the 8 electrons come from the full s and p orbitals and not the d orbitals (2 +6 = 8)?

Rian Montagh 2K

Ionization energy is the energy it takes to form an ion of that atom, aka to remove a valence electron. Electronegativity is how likely an atom is to attract an electron. They are basically opposites, so an atom like F has high ionization energy because it does not want to lose a valence electron (i...

Rian Montagh 2K

Valence electrons are the electrons in the outermost shell of an atom, and atoms are more stable when they have a full valence shell. Is this number of electrons always 8? For example, Fl has 7 valence electrons, so it forms the ion Fl- to have 8 valence electrons to be like a noble gas. Is a full v...

Rian Montagh 2K

I read more about what happens when the photon energy equals the threshold energy and one thing I found is that that electron with zero kinetic energy could fall back to the metal and release a photon the same as that one that emitted the electron in the first place.

Rian Montagh 2K

In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line. Can someone explain this problem with steps and intermediate numbers as we...

Rian Montagh 2K

To respond to the first question, l can be different numbers so if you only have n=2, then l can be 0 or 1. So I think it would make sense to choose the higher l so that you include the widest range of m values that cover all the possibilities of m.

Rian Montagh 2K

I'm very confused about the wave model of light with the magnetic and electric fields, hence electromagnetic radiation. Can someone give a general explanation of what the two fields have to do with light?

Rian Montagh 2K

I think you're referring to the photoelectric effect, where light is shined on a metal to eject electrons to see how much energy is needed to do so. Spectroscopy is the analysis of light emitted or absorbed by a substance with a spectrometer (you analyze the specific wavelengths/spectral lines). For...

Rian Montagh 2K

I was looking at the electromagnetic spectrum and I saw that microwaves have longer wave lengths, lower frequency, and less energy than visible light, so why do they heat up our food while visible light doesn't?

Rian Montagh 2K

So for glucose, the empirical formula would be CH2O, with a 1:2:1 ratio of C:H:O atoms.

Rian Montagh 2K

Oh wait does it have to do with the fact that they used 12.000 g and the atomic mass for C is 12? So it's a 1:1 ratio...?

Rian Montagh 2K

I'm confused about why the atomic masses on the periodic table are the amount of grams in a mole of that element. In other words, I know that the atomic masses are the molar masses for elements, but I don't understand why they are. What do the atomic masses, (which are in amu?) have to do with the a...

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