CHEMISTRY COMMUNITY

Justin Folk 3I

WHat's this about concentration?

Justin Folk 3I

Does heat transfer happen when the balloon loses air?

Justin Folk 3I

They orient the molecules in a way that makes them easier to crash in the correct orientation.

Justin Folk 3I

Is the salt bridge also connected to, say, Pt(s)? or just metal wire?

Justin Folk 3I

You can tell because of the cell potentials. Overall cell potential has to be positive.

Justin Folk 3I

Questions like which?

Justin Folk 3I

Yes rate law is only the slow step

Justin Folk 3I

Justin Folk 3I

What about units for a 1.5 order?

Justin Folk 3I

You could use the linear equations for the standard rxn numbers to find the constant from initial and time concentrations

Justin Folk 3I

But if you multiply entire reaction by 2 then why isn’t it using 2 moles?

Justin Folk 3I

Because for second order reactions the y-axis is 1/[A]. As time progresses the concentration of [A] decreases (assuming A is reactant) and thus 1/A increases, therefore slope of graph >0

Justin Folk 3I

1) Double reaction and initial rates are doubled: let's pretend A --> B, [A] = c mol/L and rate = k [A]^1. Your rate would be k*c^1 = kc But let's say [A] = 2c, then rate would be k*(2c)^1 = 2kc So for first order with respect to a reactant, doubling the concentration would give you double the rate

Justin Folk 3I

They basically mean, in crass terms, "How much does the concentration of reactant affect rate of reaction"

Justin Folk 3I

Yes, slope should be zero. It's the derivative of a constant, which makes it zero.

Justin Folk 3I

How do we know it's a mole of reaction?

Justin Folk 3I

Determined by the balanced equation or no?

Justin Folk 3I

Yes i believe so. Thanks for the tip. Got stuck on this one

Justin Folk 3I

Red Cat-- reduction at cathode
An Ox-- anode oxidation

Justin Folk 3I

I thought we can only measure change in entropy?

Justin Folk 3I

Yes, you're right sorry. THere's multiple R. You need to look at the units, on the third row of equation sheet. THanks

Justin Folk 3I

No, closed is just where matter can't escape. isolated is where neither matter nor internal energy can escape

Justin Folk 3I

The heat capacity is defined as ENERGY per TEMPERATURE

Justin Folk 3I

So since it's for a change its always used?

Justin Folk 3I

For example pushing a cart is work being done. You use some energy (instead of to heat up) to push the cart.

Justin Folk 3I

Because gas has more "randomness" by intuition. THere is inherently order in a liquid and solid-- they are all contained and there is only a set place that they can go. Gravity dictates this in a liquid and the lattice of a solid dictates this

Justin Folk 3I

KJ, or KJ per mole. depends on the context.

Justin Folk 3I

Heat constant. When do you use 8.314 and when do you use 0.00821?

Justin Folk 3I

The calorimeter is usually calibrated well so that there is little heat lost that is not absorbed by the substance you are measuring heat. Thus you can measure the heat of a reaction, and thus you can also measure the heat per mole (by measuring the amt. of substance consumed)

Justin Folk 3I

Bond enthalpy is equal to enthalpy of formation in a diatomic molecule; for the others it is the sum of the bond enthalpies i believe. Correct me if wrong

Justin Folk 3I

Think of it as enthalpy of formation being the same for each substance no matter whether it is on reactant or product side. Thus, if reactants - products = H, products - reactants = -H

Justin Folk 3I

You might also be able to think of it as fusion being the heat it takes to put together, which is the reverse and equal in absolute value to the heat it takes to break apart?

Justin Folk 3I

Is standard enthalpy of formation based on forming from the gaseous state as well?

Justin Folk 3I

KNO2 has NO2- when it dissociates, which it will because any compound with K+ will dissociate (generally).

Therefore, we have an initial concentration of NO2- to plug into ICE box

Justin Folk 3I

Why do we want strong base/strong acid to be the titrant?

Justin Folk 3I

No, pH is the measure of the [H+], while pKa is the measure of basically how much of a given acid HA dissociates. They are related, though. While Ka value doesn't tell too much about H+ concentration (due to other things like diprotonations, 2 H+ / mol acid), if everything else is held constant, suc...

Justin Folk 3I

No, usually not. The only strong acids are the ones that are listed as "strong acids," and we know this because a Ka value doesn't exist-- everything dissociates so [HA] == 0, and Ka becomes undefined. Theoretically, you could deduce based on electronegativity its ionic vs covalent charact...

Justin Folk 3I

Just molarity, since all units are the same, and some have varying degrees, so it wouldnt make sense to have units.

Justin Folk 3I

Bonds work because of a balance of attraction between electrons and protons, and that they're not so close that the protons in the nucleus repel each other. Therefore, shorter bonds are better because the protons can easier "grab" the electrons.

Justin Folk 3I

They are inversely related-- electron affinity is the energy required to eject an electron, while electronegativity is the tendency to gain an electron

Justin Folk 3I

Will we be given that it is a hydrogen atom? This only works for hydrogen, but the problem 8 in the practice quiz 2 didn't list it as a hydrogen atom.

Justin Folk 3I

Those shapes are right, but important to note that it's not the "boundary," but rather the probability region-- where an electron is most likely to be-- if I understand correctly!

Justin Folk 3I

I believe nitrogen has an electron affinity so much lower because it has (relatively) much fewer protons than oxygen and fluorine. Also what Alexis said about stability and all orbitals being half-filled: most stable when either all half-filled or all filled

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