CHEMISTRY COMMUNITY

Courtney McHargue 1I

Is there ever an activation energy that is so large that the reaction can't proceed? What causes this/can this occur suddenly because of something in the reaction?

Courtney McHargue 1I

What factors alter how large or small the activation energy of a reaction is?

Courtney McHargue 1I

Do these general rate laws work for every order of reaction? Are there any exceptions?

Courtney McHargue 1I

What factors of a reaction affect its K value?

Courtney McHargue 1I

Do we only have to know how to do 0-2nd order reaction calculations? And are the calculations similar or are they derived differently?

Courtney McHargue 1I

Are there any special rules or types of chemicals that aren't included when calculating the standard cell potential?

Courtney McHargue 1I

Why is max potential when very little current flows instead of when max current flows through the cell?

Courtney McHargue 1I

Is there ever a galvanic cell reaction that creates electrical energy without making a physical difference on the anode/cathode?

Courtney McHargue 1I

What do you do if delta H isn't consistent? Can you still use this formula?

Courtney McHargue 1I

What factors influence the value of delta G in a reaction? Is it mainly influenced by what's present in the reaction or what is produced/given off?

Courtney McHargue 1I

Are there any characteristics of a reaction that would hint at the value of delta G being positive/negative or larger/smaller?

Courtney McHargue 1I

An open system is any that has openings where matter and heat can be transferred into/out of, such as an open top cup. A closed system is one that doesn't have any physical openings, but can transfer heat through its walls, such as a closed box. And an isolated system is one that doesn't have any ph...

Courtney McHargue 1I

If it's closed then matter can't be added or taken away from the system, such as a closed box, but heat can still transfer into and out of it. If the system is isolated, then it's like a highly insulated box where matter and heat both can't be transferred into or out of the system.

Courtney McHargue 1I

Is there ever a situation where the change in internal energy is affected by factors other than heat and work?

Courtney McHargue 1I

What's the difference between extensive and intensive properties (heat capacity vs specific heat capacity) and does it change how/when we use those things?

Courtney McHargue 1I

Since heat capacity and specific heat capacity are one calculation apart, when asked about heat capacity in a question should we assume they're asking about specific heat capacity? Will normal heat capacity ever be asked about?

Courtney McHargue 1I

What's the difference between normal calorimetry and bomb calorimetry? Does normal just have constant pressure but anything else can change and bomb is the same idea but only volume can change?

Courtney McHargue 1I

When you're calculating the pH of a salt solution do you always ignore the ions that don't take part in the reaction and dissolve away?

Courtney McHargue 1I

What's the difference between % ionized vs % deprotonated? Are there different names that mean the same calculation?

Courtney McHargue 1I

For percent protonation is it the final concentration of the weak base over its initial concentration x100 or the concentration of the conjugate acid over the initial concentration of the weak base x100?

Courtney McHargue 1I

How do we find the pH/pOH and concentrations of H30+ and OH- of a reaction with a weak acid/base that doesn't completely dissociate?

Courtney McHargue 1I

Because of the same idea, if there are more moles on the right and pressure is added then the reaction will try to balance itself out by favoring the reverse reaction and going back to reactants.

Courtney McHargue 1I

The subscripts don't matter in the ice table, only the coefficients before the molecules of product or reactant affect the change in molarity in the ice table calculations and the powers the molarities are to in the final equilibrium constant calculation.

Courtney McHargue 1I

If you're dealing with solutions that have a given concentration, then you use Kc, but if you're dealing with gases and partial pressures, you use Kp.

Courtney McHargue 1I

How do you calculate the equilibrium constant if you're given a mix of concentrations and pressures? Or will that never happen?

Courtney McHargue 1I

What's the physical and chemical difference between ideal and real gases?

Courtney McHargue 1I

Ka tells you how well an acid dissolves in solution, but when simplified into pKa, the smaller the value is the stronger the acid, as strong acids dissociate more in solution.

Courtney McHargue 1I

What aspects of an acid/base's lewis structure tells you if it's an acid or base?

Courtney McHargue 1I

Is water's identity as an acid or base solely determined by being the opposite of what it's reacting with?

Courtney McHargue 1I

Is hybridization always based off of the number of bonds or lone pair electrons around the central atom or are there other factors that could affect it?

Courtney McHargue 1I

What are the main differences between Bronsted and Lewis acids and bases?

Courtney McHargue 1I

What factors determine how strong or weak an acid/base is?

Courtney McHargue 1I

I think we don't have to know how to draw the 3-D hydbridization diagrams, but that we have to know how to make the electron configuration and understand how it works.

Courtney McHargue 1I

Do single, double and triple bonds always have to be made from the exact number of sigma and pi bonds each time, or can they be made with other ratios of the two?

Courtney McHargue 1I

Is a VSEPR model shape always polar if the central atom in the lewis structure has lone pairs? Or can lone pairs be symmetrical and cancel out charges to make the molecule non-polar?

Courtney McHargue 1I

What are all the factors that affect molecular shape determined from the lewis structure?

Courtney McHargue 1I

Why are ionic bonds stronger than hydrogen bonds?

Courtney McHargue 1I

When you make a lewis structure that has resonance you need to draw all the resonance structures with double-sided arrows between them, as the correct lewis structure for the molecule is actually a hybrid of them all and not any single one.

Courtney McHargue 1I

Any element in the third period or below can have an expanded octet with more than 8 valence electrons. They do have a d-orbital and are large enough to stably hold more electrons in their shells. But, if you have more that 8 electrons in your lewis structure for a certain molecule, try to make sure...

Courtney McHargue 1I

To find the most ideal lewis structure you want to create one where the base element, or element in the center of the structure, has a formal charge of 0. If the overall molecule is an ion with a charge, then try to have the outer elements which are connected to the main base be the ones that carry ...

Courtney McHargue 1I

Formal charges don't always have to be zero, as if a molecule is an ion with a certain positive or negative charge, then at least one element in the structure must have a charge that makes all of the formal charges of the elements in the structure add up to zero. But, to find the most stable form of...

Courtney McHargue 1I

Lavelle said that elements in the third period and below are able to hold more than 8 valence electrons and stay stable. Since sulfur (S) is in the third period it can follow this rule, which is why it can hold 12 electrons.

Courtney McHargue 1I

Lavelle said that elements in the third period or below are able to hold more than 8 valence electrons, typically sulfur, silicon, phosphorus and chlorine are the main ones known to have this ability.

Courtney McHargue 1I

If a molecule has resonance you must draw each possible lewis structure, bracket each structure, and draw double-sided arrows between them. In real life no single resonance lewis structure is "right," but the molecule is a hybrid of all the possibilities.

Courtney McHargue 1I

Most elements need to have a complete octet of valence electrons in order to survive and be stable. Only certain elements such as sulfur, phosphorus, chlorine and silicon can hold more than 8 valence electrons and form a stable expanded octet and elements such as hydrogen can only handle 2 valence e...

Courtney McHargue 1I

Atoms can be bonded together in the lewis structure in any pattern, but each main element, other than H, needs to have a full set of 8 electrons by the end. By using single, double and triple bonds, you can use the amount of valence electrons available and start to form the structure, experimenting ...

Courtney McHargue 1I

There is no particular order that you have to put the elements of the structure in, as long as each main element has a full set of 8 electrons, other than elements like H which only need 2 electrons.

Courtney McHargue 1I

Just remember that the SI base units are kilograms(kg) for mass, meters(m) for length and seconds(s) for time. Then make sure you know the prefixes, such as mega, kilo, deci, centi, milli, etc, and the powers of ten from the original SI unit they represent.

Courtney McHargue 1I

Since 0.25 isn't followed by any other decimal values after the 5, normally this answer would and should be rounded to 0.2 since both of the values getting you to this answer had only one significant figure.

Courtney McHargue 1I

In today's lecture we talked about De Broglie's Wave Equation, I don't understand how a photon can have momentum when it doesn't have a mass?

Courtney McHargue 1I

I always start by balancing the more unique elements that only occur once on each side of the reaction equation. I then balance the more common elements that show up multiple times throughout the equation, such as H, O and C. After that I can finish balancing the equation with any elements that are ...

Courtney McHargue 1I

When I find the limiting reactant I always use the molar masses of the reactants to find how many moles of each the reaction has. After I do that I look at the molar ratios between the reactants to see how much of each is needed to react with the other. In the example 2A + 1B --> 3C, for every 2 mol...

Courtney McHargue 1I

Actual yield is the amount of product formed when performing the reaction in real life, theoretical yield is the maximum predicted amount of that same product formed if the reaction completely uses up its limiting reactant and doesn't lose any product due to error. The actual yield will almost alway...

Courtney McHargue 1I

When using the formula m1v1=m2v2 always make sure the volume values you put in are in liters, and then if the question asks for the answer to be in mL or another form, convert from liters at the end.

Courtney McHargue 1I

Never round off by sig figs in the middle of the problem, but keep in mind the sig figs of each new value you are continually using in a problem. At the end of the problem look at the supposed sig figs the values you used had and then round off to that number of sig figs.

Courtney McHargue 1I

As others have said, I usually start by balancing the unique elements that only occur once that are not found in multiple reactants or products, then continue by balancing the more common elements that are spread throughout the equation, and finish by balancing elements that are standing alone, such...

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