CHEMISTRY COMMUNITY

Henry Dudley 1G

If the line is straight for a graph, then the reaction is that order. For instance if the data points give you a straight line for lnA on the y-axis and t on the x-axis, you know you have a first order reaction.

Henry Dudley 1G

Can a bimolecular reaction be third order if one of the reactants is second order?

Henry Dudley 1G

One tip I have is to not talk about the material and what you do and don't know right before the test. You're not going to learn anything in just five minutes but you can psych yourself out.

Henry Dudley 1G

Hadji Yono-Cruz 2L wrote:Should we remember all of the functional groups mentioned in the slide in lecture?

All of these posts date back to last year so I don't think this applies to our 2019 final.

Henry Dudley 1G

Are zero order reaction rates included in the rate law?

Henry Dudley 1G

Will we be expected to integrate or derive any formulas or will they be provided to us?

Henry Dudley 1G

In the textbook there are questions with answers that have units in L per mol. Why is this and how do you generally determine the units for rate constants?

Henry Dudley 1G

Is it possible for the cell potential to be negative?

Henry Dudley 1G

So if there is a solid in the reaction then you don't include Pt at the end?

Henry Dudley 1G

Should Pt always be included at the end of the cell diagram. Some textbook questions have answers that don't include a Pt or metal at the end.

Henry Dudley 1G

If the temperature is not given try the ideal gas law, however, if that isn't possible, then use k=298.

Henry Dudley 1G

An example of this would be a liquid being cooled into a solid. The molecules have less possible positions and therefore have less entropy leading to a decrease in entropy or negative entropy change.

Henry Dudley 1G

What does it mean if delta G is 0?

Henry Dudley 1G

rkang00 wrote:If a system is isolated with + amount of energy, will it there be no change even after time passes?

There will be no change regardless of the amount of time passed. However, this is not the case for open and closed systems.

Henry Dudley 1G

Just to add to the previous response, only elements, compounds, molecules, etc. that are not in their most stable states have enthalpies of formation that are not 0.

Henry Dudley 1G

Is KJ per mol an acceptable unit of measurement when solving for the change in internal energy?

Henry Dudley 1G

Kobe_Wright wrote:The outline says through entropy but gibbs free energy is last and theres a few other things so what is it?

The end of entropy, according to Friday's lecture, is finding the total change in entropy of the reaction based on the entropy of the products and reactants.

Henry Dudley 1G

Kavvya Gupta 1H wrote:I know Sonia said she would post the sheet she made with questions that are similar to what questions are going to be on the midterm from today's review session, but I don't know when she's going to post it.

Where on Chemistry Community can this worksheet be found?

Henry Dudley 1G

If the pressure is not stated, it is assumed to be 1 atm. So in this case, it is assumed that the pressure is constant at 1 atm.

Henry Dudley 1G

Why does a system carried out reversibly do more work than that of an irreversible system?

Henry Dudley 1G

Does an isolated system have a fixed volume?

Henry Dudley 1G

Usually you would want to use either the enthalpy of formation or of combustion methods. These are the most accurate and easiest to use. Using the mean bond enthalpy is less accurate and it can get confusing at times. It really depends on what equations you are given and what values you know. There...

Henry Dudley 1G

Yeah how do compounds like CO2 in the form of dry ice go straight from being a solid to a liquid? Does CO2 even have a liquid state, and if not, how is that possible?

Henry Dudley 1G

Are there any modules for any of the other topics or was it just chemical equilibrium?

Henry Dudley 1G

So the burn was worse due to more energy being exerted on the skin? But, how does that energy manifest if it does not cause an increase in temperature? In other words, what happens to that excess energy? What is it doing if it isn't heating the steam?

Henry Dudley 1G

High pKa= weak acid/strong base
Low pKa= strong acid/weak base

High pKb= weak base/strong acid
Low pKb= strong base/weak acid

Henry Dudley 1G

I don't think so since it hasn't been discussed in lecture and is only featured in two of many homework problems.

Henry Dudley 1G

So one dead giveaway of a wake acid or base is the presence of acidity or basicity constant (Ka or Kb respectively). Only a weak acid/base would have one of these. A chemical reaction involving a weak acid/base would have a double arrow, as some of the reactants would form back from the product thr...

Henry Dudley 1G

So partial pressure is parentheses and concentration is brackets?

Henry Dudley 1G

Simran Rai 4E wrote:Adding an inert gas wouldn't affect the equilibrium because the concentrations of the reactant and product would remain the same, meaning there would be no change in the equation.

But if the volume changes, how is there not a change in the concentration if the concentration is affected by volume?

Henry Dudley 1G

What is the value of R?

Henry Dudley 1G

In the reaction Ba(OH)2 + H2O = Ba + 2OH + H2O, the conjugate base is H2O and the conjugate acid is OH. Whatever was the base before the reaction becomes the conjugate acid and whatever was the acid before the problem becomes the conjugate base.

Henry Dudley 1G

Iris Bai 1E wrote:Ka is the equilibrium constant for acids, and Ka is the equilibrium constant for bases. For an acid that is ionized, you would fine Ka, not Kb.

How would you find Ka?

Henry Dudley 1G

Alana Sur 3B wrote:I don't think we don't need to remember the constants but you should know the formula for calculating Ka and Kb

The formula for calculating Ka is just -log(PKa) and the formula for calculating Kb is just -log(PKb) right?

Henry Dudley 1G

Pi bonds overlap side by side with sigma bonds preventing them from rotating.

Henry Dudley 1G

Polarizability is the measure of an atom's electron cloud's ability to become distorted by an anion. Polarizability follows the same trend as atomic radii on the periodic table.

Henry Dudley 1G

What are some of the main physical property differences between acids and bases?

Henry Dudley 1G

Hydrogen is an intermolecular force between the hydrogen in one molecule being attracted to a hydrogen/oxygen/nitrogen/fluorine in another molecule. For example, the hydrogen in one water molecule being attracted to the oxygen in another water molecule. This is also a type of dipole-dipole attracti...

Henry Dudley 1G

What are some common exceptions when trying to determine polar or non polar based on symmetry?

Henry Dudley 1G

Why do atoms form bonds if it requires energy?

Henry Dudley 1G

charlotte_jacobs_4G wrote:Does the distance between the bonds effect the boiling point? Would this cause the bond to be stronger or weaker?

The longer the bond the weaker it is. For instance double bonds are shorter and stronger than single bonds and triple bonds are shorter and stronger than double and single bonds.

Henry Dudley 1G

In order for hydrogen bonding to occur, does there have to be a lone pair of electrons the hydrogen atom can attach to?

Henry Dudley 1G

In order to determine what kind of molecular forces you are dealing with, you need to know if the atom is polar or not. How do you determine wether an atom is polar or non polar?

Henry Dudley 1G

I think the easiest way to remember electronegativity, ionization energy, electron affinity, and atomic radius is that the first three all increase across a period, but decrease down a group. However, atomic radius is the exact opposite of that meaning if you can remember atomic radius and you can r...

Henry Dudley 1G

Aidan Ryan 1K wrote:On a similar note, what is polarizing power compared to polarizability. Also are these only for ions?

Yes polarizing power is only for ions because it is a measure of the ability of one ion to polarize another ion or atom.

Henry Dudley 1G

This might be a very elementary question but what is a dipole?

Henry Dudley 1G

Is ionization energy related to formal charge because I thought the central atom was the one that always had the lowest formal charge.

Henry Dudley 1G

Once the first electron is removed, the atom becomes a positive ion. It has an overall positive charge, so removing another electron from it would be much harder than removing an electron from a neutral atom due to the electrostatic attraction between the nucleus and electrons. Does this mean remov...

Henry Dudley 1G

If a metal bonds with a nonmetal is this considered a covalent bond?

Henry Dudley 1G

What is the difference between a cation and an anion?

Henry Dudley 1G

Are covalent radius and atomic radius equal?

Henry Dudley 1G

What is the difference between R(1/n1^2 - 1/n2^2) and -hR/n^2?

Henry Dudley 1G

If black bodies are only theoretical, then why does the book refer to heated metal, or a "hot object" as black body?

Henry Dudley 1G

Yes it is the range of the area we know that the actual number is in

Henry Dudley 1G

No, h bar is not a constant it is just shorthand for pi/2.

Henry Dudley 1G

"I cannot conceptualize light being both photon (PACKETS) of energy and wavelengths. I find it difficult to exercise this into equations when I do not understand how it can be both and have one number. Please explain and possibly use equations in your explanation if possible. If not that is ok...

Henry Dudley 1G

Don't know if this is how it's defined in this class but you can think of it as what happens when a massive bulky object that absorbs all radiation and then emits its own form of radiation. One example would be like a burner of an oven that heats up and changes color as it gets hotter from black to...

Henry Dudley 1G

Different metals have different threshold energies because they have a different number of protons, electrons, and energy levels. If the metal has many protons and electrons, there will be more energy levels, resulting in the electrons being further away from the nucleus. These negatively charged e...

Henry Dudley 1G

Danny Elias Dis 1E wrote:What was the unit of measurement only used by chemists, also known as 10 to the -10 power?

The unit that is 10^-10 is the Angstrom which has the symbol Å.

Henry Dudley 1G

I think the "pm" you're referring to is the measurement unit of a picometer, which is 10^-12! So to convert that to the unit of a meter which most questions have been using, you would multiply your answer by 10^12. You're right the picometer is 10^-12 and you would multiply by 10^12 to ge...

Henry Dudley 1G

How do significant figures work when the number is larger for instance if there was a problem that said find how many moles of hydrogen are in 2.00 kg of H. The answer is 1,984.127 but how do we know how many significant figures there are when you need more digits just to get back to 0 than were giv...

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