CHEMISTRY COMMUNITY

Shuyi Yu 1B

Why does raising the temperature increases the rate constant of reactions with higher activation barriers more than it does the rate constant of reactions with lower activation barriers?

Shuyi Yu 1B

Will we ever be expected to know/find non-integer (like 1.5) reactant orders?

Shuyi Yu 1B

In the textbook, at the end of section 15.6, it gives a table detailing all the components of each order of a reaction. For the half-life of a second-order reaction, it writes that the equation is t1/2=. However, underneath that, it says "(not used)." Does anyone know what this means/why t...

Shuyi Yu 1B

Do we have to learn the steady state approach in the book or should we just study pre-equilibrium one he taught us in lecture?

Shuyi Yu 1B

Will the problems always state which step is fast and slow so that we could determine the rate determining step or do we have to some how figure it out based on the context given?

Shuyi Yu 1B

How can we tell from a reaction profile whether a reaction is spontaneous? I understand that it must be energetically favorable, but at what point is the activation energy low enough? Do we just assume that it is low enough when the hump is relatively low?

Shuyi Yu 1B

What are the axises for the 2nd order Integrated Rate Law Graph? I know that the first order rate law graph is ln[A] vs. time.

Shuyi Yu 1B

How does one know whether a reaction is first order or second order using the graph?

Shuyi Yu 1B

When we're asked to find the rate of consumption or rate of formation of a molecule in a reaction, when is it necessary to divide (change in concentration)/(change in time) by the number of moles of that molecule?]

Shuyi Yu 1B

I understand that for a cell diagram, the anode is on the left, the cathode is on the right, and the electrodes are at the ends... but within the anode or cathode, does it matter what order you write the species in?

Shuyi Yu 1B

How does a salt bridge work? The textbook says that its to prevent contact between the two aqueous solutions because when different ions mingle they can affect the cell potential but its function is described as "allowing the flow of ions" wouldn't this mean its letting them meet?

Shuyi Yu 1B

Why do we subtract anode from cathode from in order to calculate the cell potential?

Shuyi Yu 1B

While the two Gibbs Free Energy formulas are both applicable, how do we distinguish when to use which? For example, if given the concentrations of the products and the reactants, will we then use the deltaG=-RTlnK?

Shuyi Yu 1B

Why is it that when Gibbs free energy of the system is negative then the process is spontaneous and the delta S universal is positive? How does delta G being negative make the process spontaneous?

Shuyi Yu 1B

A system is spontaneous when Delta G is negative and also when Delta S total is positive. Why can't we tell the spontaneity of a system by looking at Delta H?

Shuyi Yu 1B

When calculating standard reaction enthalpy, entropy, and Gibbs free energy from formation values, why do the answers have units with /mol? Shouldn't /mol cancel out since you multiply by the coefficient in the calculation?

Shuyi Yu 1B

Is there a preferred way to describe a change in entropy of a system? Rather than just saying the amount of disorder within the system has increased or decreased how can we be more specific in this description?

Shuyi Yu 1B

If deltaH is positive and deltaS is negative, what is the spontaneity?

Shuyi Yu 1B

For entropy, which equations do you use for isothermal reversible vs. irreversible free expansion? What does free expansion mean?

Shuyi Yu 1B

Why is the total entropy in the universe 0 (Entropy system = Entropy surroundings) for reversible processes?

Shuyi Yu 1B

How do you know when to use 3/2 R instead of the specific heat capacity provided on the cover sheet?

Shuyi Yu 1B

Can all elements be converted into solid, liquid, or gas states given that the right amount of energy and pressure is applied?

Shuyi Yu 1B

Reversible and irreversible processes have different equations but what exactly is the difference between the processes? How can the differences be logically explained?

Shuyi Yu 1B

I get that temperature and heat are different things but how they are related. For example, does an increase in temperature always lead to an increase in heat content (or the other way around). Also is energy just another term for heat content?

Shuyi Yu 1B

If you are given a molar concentration for a molecule with a stoichiometric coefficient does that concentration need to be multiplied by the stoichiometric coefficient to find the concentration of the single molecule?

Shuyi Yu 1B

I know that 10^-5 or lower is when we can disregard the x but if something is 10^-4, can we still disregard and just check that the x value divided by the initial concentration is less than 5%

Shuyi Yu 1B

If the concentration of each reactant and product increased by the same amount, would K also increase or would it stay the same since it is a ratio?

Shuyi Yu 1B

If Q and K both have the same formula why are they not equal to each other?

Shuyi Yu 1B

When do we use concentration to find the equilibrium constant and when do we use partial pressure to find equilibrium constant? Will the question ask for one of the two specifically?

Shuyi Yu 1B

In the textbook the units are in bars but in Lavelle's slides he uses atm. Would we need to know how convert between the two during tests or will the question give us the units?

Shuyi Yu 1B

When writing the chemical formula for water, would it matter if we use "H2O" or "OH2"?

Shuyi Yu 1B

What does it mean to have a poly- versus a mono-dentate compound and does it affect the naming of the compound?

Shuyi Yu 1B

Yes. The pH + pOH = 14. The two expressions are opposites expressions. As the pH increases the pOH decreases and vice versa. Both values equal 14.

Shuyi Yu 1B

why do we subtract the pOH from 14 to find the final pH?

Shuyi Yu 1B

is it ever possible to get a negative pH? if so could someone explain how this could happen?

Shuyi Yu 1B

when we calculate the pH and pOH do we still take into account sig figs in the final answer?

Shuyi Yu 1B

Is drawing the molecular shape of a molecule the only way to determine bond angles?

Shuyi Yu 1B

Will we need to know how to draw d orbitals and know their shapes? I know that we need to know this for the s and p orbitals but I was wondering what exactly we need to focus on for the d orbitals.

Shuyi Yu 1B

Whats the difference between pi and sigma bonds? And why can there be two pi bonds but not two sigma bonds?

Shuyi Yu 1B

In a molecule with a square planar structure will the angles between the remaining 4 bonded atoms remain 90 degrees? Or will the repulsion push them closer together?

Shuyi Yu 1B

In a double or triple bond why is the region of electron density equal one instead of two or three?

Shuyi Yu 1B

I came across a VSEPR chart and thought I'd share it.

Shuyi Yu 1B

Do we need to draw lewis structures in a way that reflects the molecular shape? Also for future tests would it matter where we draw the lone pair in lewis structures?

Shuyi Yu 1B

If a trigonal pyramidal forms a coordinate covalent bond with its lone pair and its shape becomes a tetrahedral, would the bond angle become 109.5 degrees?

Shuyi Yu 1B

When there are two central atoms how would you name the lewis structure and use VSEPR to classify its shape?

Shuyi Yu 1B

For different exceptions of the octet does the FC need to be fixed to zero or do the rules that the octet had overrule?

Shuyi Yu 1B

How do single, double, and triple bonds affect formal charge?

Shuyi Yu 1B

When making Lewis Structures and deciding where to use double bonds how can we determine which version is more stable?

Shuyi Yu 1B

Does orbital f correspond to all values of n greater than or equal to four and all values of l greater than or equal to 3?

Shuyi Yu 1B

What does it mean for an electron configuration to represent a ground or excited state of an atom? Is it talking about the same/opposite spin?

Shuyi Yu 1B

Can the relationship between n, l, and m be described as shell, sub-shell, and orbital within a sub-shell, respectively? And does the value of l tell you the highest possible sub-shell of that particular energy level?

Shuyi Yu 1B

For exams how should we label electron configuration? For example, 2px^1 2py^2 2pz^3 is the same thing as 2p^3 so which format would be preferred on exams.

Shuyi Yu 1B

Whats the difference between shell, subshell, and an orbital? I've seen those terms being referred to in problems but I wasn't sure what the difference was between the three.

Shuyi Yu 1B

When writing the ground state of an element would it still be okay to order it as 4s2, 3d10 instead of 3d10, 4s2 even though 4s2 is filled in first. The answers to these problems are sometimes switched.

Shuyi Yu 1B

I had to make these bad chemistry jokes

because all the good ones Argon.

Shuyi Yu 1B

Do you know any jokes about sodium hypobromite?

NaBrO.

Shuyi Yu 1B

What do you do with a sick chemist?

If you can't helium and you can't curium then you might as well barium!

Shuyi Yu 1B

For some of the homework problems I got answers that are off by a few numbers because of sig figs and rounding. Would my answers still be correct and what is the accepted range for the answers?

Shuyi Yu 1B

When finding the molar mass in the periodic table how many sig figs do we use?

Shuyi Yu 1B

Riley Dean 1D wrote:Does anyone know when the cutoff for week one's discussion period is? Like how long we have to post for week one and when week two starts?

I think the cutoff is on Fridays. So basically three posts by Friday week one, three posts by Friday week two, etc.

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