CHEMISTRY COMMUNITY

Kirsty Star 2H

The overall order of a reaction comes from the addition of the two exponents "n" and "m" which for single step reactions are equal to the stoichiometric coefficients of the reactants

Kirsty Star 2H

For 0 order reactions, the units for k are M/s, for 1st order reactions, the units for k are 1/s, and for 2nd order reactions the units for k are 1/M*s. With M being molarity or concentration

Kirsty Star 2H

I think the unique rate of reaction is in the form:
-1/a * dA/dt = 1/b * dB/dt = 1/c * dC/dt for an equation like aA --> bB + cC

Kirsty Star 2H

n isn't just moles and probably isn't given in the problem. n is moles of electrons transferred once you balance the redox half reactions

Kirsty Star 2H

Once you do what those people mentioned, I believe the balanced reaction comes out to 2 e-. So n = 2

Kirsty Star 2H

Under what conditions do ΔG and ΔG° = 0 respectively?

Kirsty Star 2H

This equation is exactly the same if it were (v2/v1) since from the ideal gas law pv=nRT, you know that pressure and volume are inversely proportional. it just depends what the problem gives you

Kirsty Star 2H

Lavelle said that reversible reactions are pretty much entirely theoretical, since it's pretty much not possible for all heat to be converted to work with nothing being lost to the surroundings. Most reactions are irreversible, especially biological reactions.

Kirsty Star 2H

Yes, reversible reactions are actually just theoretical, since it would mean that all energy in the form of heat can be transferred to work, with nothing being lost to the surroundings, which is almost never possible. Lavelle said almost every reaction is irreversible, especially biological applicat...

Kirsty Star 2H

Agreed. You know which one to use in the context of the problem, so it's important to identify what is being held constant in the given problem

Kirsty Star 2H

If there is a change in volume and in temperature, you split the problem up into two steps, first using the deltaS equation with V2/v1 and then using the equation with T2/T1. These two deltaS values added together are equal to the deltaS of the whole system

Kirsty Star 2H

How can you tell if increasing temperature will increase or decrease the stability of a molecule?

Kirsty Star 2H

So for an irreversible reaction where pressure is constant, the equation is w = -PΔV and for a reversible reaction where pressure is constantly becoming smaller, the equation is w = -nRTln(v2/v1). Is this right?

Also, where does the equation ΔU = 3/2nRΔT come from?

Kirsty Star 2H

An isolated system cannot exchange energy or matter with the surroundings, which pretty much means that pressure can't change, so yes, an isolated system would have constant volume

Kirsty Star 2H

How does the equation ΔU = q + w change when ΔP is 0 and ΔV is 0 respectively?

Kirsty Star 2H

Since diatomic molecules are the most stable form of those elements, those elements pretty much only occur in that state, so the bond enthalpies are known an accurate. Bonds between other elements, like Carbon for example, can be found in multiple different molecules. Therefore the enthalpies of the...

Kirsty Star 2H

A state function is something that doesn't depend on the path taken to get to a certain state, but only depends on the initial and final states. Another state function is volume. For example, if a bucket first had 5 L of water, then someone added 3 L and then took away 6 L, you end up with 2 L, and ...

Kirsty Star 2H

The first method is Hess's Law, which you use when you know the deltaH of two different reactions and are able to combine them to find the deltaH of the new reaction. The second method uses bond enthalpies, since in chemical reactions, bonds in reactants and broken and bonds in products are formed. ...

Kirsty Star 2H

Solid --> Liquid --> Gas is endothermic (surroundings get warmer)
Gas --> Liquid --> Solid is exothermic (surroundings get cooler)

Kirsty Star 2H

How I understood this idea is that when water comes into contact with skin, it is already in liquid form and does not change state, therefore it's temperature decreases, releasing energy. When steam comes into contact with the skin, it does change state, from gas to liquid. During this condensation ...

Kirsty Star 2H

K values of gas phase reactants and products can be solved as either Kp or Kc, depending on what is given. However, k values for aqueous reactants and products can only be written in Kc.

Kirsty Star 2H

On one problem regarding H2SO4, I was confused about the same thing, since the textbook just said Ka1 was "strong" and didn't actually have a value. In this case I used Ka2 which was given, however I think that if Ka2 is significantly less than Ka1, then you're just supposed to use Ka1

Kirsty Star 2H

If the K value is greater than 10^-3, that is when we cannot disregard x and have to solve using quadratic equation

Kirsty Star 2H

In an ice chart, are the values for change for reactants always negative and the products positive? Or does it depend on the direction the reaction will proceed?

Kirsty Star 2H

Typically a "small" value of K is < 10^-3 and a "large" value is > 10^3. Any K value in between is viewed as intermediate, in which neither reactants or products are favored.

Kirsty Star 2H

I remember learning about things that "shift" equilibrium in high school, but Dr. Lavelle said to avoid that word. Could someone explain to me what he means by equilibrium "sitting" to the left and not "shifting" to the left?

Kirsty Star 2H

The initial concentration of products isn't always 0, though. Sometimes it will be given information in the problem. Usually if it's not given, we assume it's 0.

Kirsty Star 2H

We are still not expected to do any calculations with Schrodinger’s equation right?

Kirsty Star 2H

When showing a polypeptide acid dissociating it should have both steps right? Or should we simplify into 1 step

Kirsty Star 2H

Are both AX2E and AX2E2 bent shaped? Is there a difference?

Kirsty Star 2H

How do we know the shape of a coordination compound? Does it have to do with the number of bonded ligands?

Kirsty Star 2H

Does the number of ligands bonded to the central determine the shape of the coordination compound?

Kirsty Star 2H

If something asks for the hybridization of a central atom, is sp3 (for example) enough? Do we need to include the 2sp3 if it happens to be in the second row of the periodic table?

Kirsty Star 2H

Amphoteric simply means a compound that can act as either an acid or a base depending on the strength of the acid or base being added to it.

Kirsty Star 2H

Can someone define amphoteric for me?

Kirsty Star 2H

The difference between bronsted and lewis acids is basically if you're focusing on H+ ions or electrons. Bronsted acids donate hydrogen ions and bronsted bases accept hydrogen ions where as lewis acids accept a lone pair while lewis bases donate lone pair.

Kirsty Star 2H

So it depends on which atom (O or H) is bonding to the central transition metal?

Kirsty Star 2H

Thank you!

Kirsty Star 2H

When should the ligand of water be written as OH2 versus H20?

Kirsty Star 2H

Is there a rule for which ligand should be named first?

Kirsty Star 2H

A dipole moment occurs when one atom in a molecule (or one side of a molecule) is more electronegative than the other, meaning that it attracts electrons. This attraction causes a net negative charge on one end of the molecule and consequently a positive charge on the other end. This polarity within...

Kirsty Star 2H

I agree I think the next test will be mainly covering chemical bonds and molecular shape and structure.

Kirsty Star 2H

Do higher melting points work in the same way? Stronger bonds means higher melting point?

Kirsty Star 2H

I don't understand why in order of increasing ionization energy, it goes C O N F. I thought it would be C N O F. Anyone know why?

Kirsty Star 2H

I am struggling to conceptualize the idea of using diameter as a delta X value... can someone explain how the diameter of something, for example an alveoli sac, is also equal to the uncertainty in position of something within that diameter?

Kirsty Star 2H

The De Broglie equation can be used for any object that has rest mass, because it was found that just as light as both wave and particle properties, electrons also have both. So, the De Broglie equation is usually used to when the object's wavelength we are told to find has mass. If we are doing pr...

Kirsty Star 2H

Something that helps me a lot is to remember that when solving for wavelength, wavelength = hc/E is used when looking at photons, whereas the De Broglie wavelength equation, wavelength = h/p is used when looking at particles that have mass.

Kirsty Star 2H

Since we know two equations involving wavelength, (c = (wavelength)(frequency) and wavelength = h/p) I was wondering when to use which equation. Does it just depend on the information given? Or are there certain times when you have to use the De Broglie wavelength versus the speed of light equation?

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