CHEMISTRY COMMUNITY

Kyither Min 2K

E˚ refers to the cell potential of a cell at standard conditions (25 degrees celsius, 1 M and 1 atm) and so it is a constant value that is given and will not change. E refers to the cell potential of a cell at any time, whether or not it's at standard conditions.

Kyither Min 2K

Temperature should only affect the rate constant

Kyither Min 2K

It will typically be told as the slow step or if it's in a proposed mechanism, I think we are expected to deduce which is the slow step based on the experimentally determined rate law.

Kyither Min 2K

an oxidation reaction when you're writing out the balanced charges and elements should have the electrons on the products side as you are losing the electrons (LEO) and the reduction reaction should have the electrons on the reactant side since they are gaining electrons (GER).

Kyither Min 2K

Both versions give you the right answer. However, on the equation sheet, the log version is a constant over n, so you have to keep in mind that the constant given can only be used if the reaction is taking place at 25 Celsius.

Kyither Min 2K

yes, the total n is referring to the amount of electrons transferred in the balanced redox reaction.

Kyither Min 2K

I like to balance it first like an acidic reaction with H+ and then to remove the H+, add OH- on both sides to neutralize the H+ to H2O. That way, you'll have H2O and OH-.

Kyither Min 2K

k is the rate constant so it's basically an indicator of how fast the reaction will happen. K is the equilibrium constant that tells you the ratio of products to reactant concentrations when the reaction is at equilibrium. Based on the relationship between k and K, we can determine that the forward ...

Kyither Min 2K

The catalyst will be needed for the reaction to occur and therefore will be present before the reaction takes place. It will then get made again (or not used up) so the catalyst will then be present before the reaction takes place and after the reaction takes place.

Kyither Min 2K

I think this was mentioned in class but zero order reactions occur when the concenctration is super high that there is barely a difference in concentration respect to time.

Kyither Min 2K

There has to be a solid in the cell to transfer the electrons. Therefore, if the reaction itself doesn't have a solid or metal we add carbon or platinum.

Kyither Min 2K

So reducing power refers to the strength of the ion/substance as a reducing agent. The ion/substance that is being oxidized is also the reducing agent. Therefore, the more the ion/substance wants to be oxidized the stronger it is as a reducing agent or reducing power. We can determine the oxidizatio...

Kyither Min 2K

The internal energy of the system would not change as an isolated system doesn't exchange energy or matter with it's surroundings and based off the conservation of energy theory, if energy isn't used or exchanged, the energy will stay constant.

Kyither Min 2K

Reversible processes are when the external pressure is changing in minuscule amounts and so the volume is changing in minuscule amounts and can return to it's original state. Irreversible processes have a constant external pressure so once it expands/compresses to a certain volume, it will stay the ...

Kyither Min 2K

It is because the definition of delta H is the change in enthalpy of a reaction under constant pressure. Therefore, you know when delta H is given, the reaction took place under constant pressure.

Kyither Min 2K

There are various ways in which one can use the constant R and so there are various units for the constant. For example, in the PV=nRT equation, one side has atm*L and the other as mol*K*R, and so to cancel so they equal each other, R has the unit and value of 0.08206 atm*L/mol*K. However, for work,...

Kyither Min 2K

An extensive property is something where the value changes based on the amount of something. For example, mass changes based on how much of a sample you have. Similarly, heat capacity on it's own changes based on how much of the sample you have. 10 g of a substance may take 10 joules to raise it by ...

Kyither Min 2K

A state function is something where the path doesn't matter, only the initial and final state. The reason it is so important is that since the path doesn't matter, you can subtract, add, multiply, and divid state functions as necessary.

Kyither Min 2K

When we look at work, the negative sign is just used to indicate which side of the system is doing work, not necessarily the amount of work. We would look at work's magnitude so we would disregard the sign change when comparing the two different systems.

Kyither Min 2K

Although the correlation is very similar, work refers to how the energy could be used/transferred and energy is the ability to do work. So just because a system has a lot of energy, it doesn't mean that work is being done because nothing may change or that energy isn't being used.

Kyither Min 2K

I would say yes that the enthalpy of a reaction refers to the heat of the reaction since all enthalpy of a reaction is, is the change in enthalpy or heat of a reaction and so that correlates to the heat given off/absorbed by the reaction. As for which of the 3 methods is best, it really depends on w...

Kyither Min 2K

pKa stands for -log of Ka and pH stands for -log of Hydronium ions. Consider the p as a function rather than a symbol. All the p does is mathematically change the value, similar to a negative sign or derivative. Ka is the dissociation of an acid or the equilibrium constant for the acid whereas H is ...

Kyither Min 2K

Yup! Enthalpy is related to states and the enthalpy change of one state will be different than the enthalpy change of a different state.

Kyither Min 2K

Only if the volume is decreased/increase. If you're adding an inert gas that would technically change pressure but would not affect the equilibrium/ shift the equation.

Kyither Min 2K

If the concentration of the hydronium ion is smaller then 10^-7, say 10^-9, the pH calculated if you use that will give you 9 - a basic solution. However, you have to keep in mind that there is hydronium ions in the water already and that concentration is 10^-7. So if you add the concentrations of t...

Kyither Min 2K

Yes, pH can be negative since pH is just the -log of the concentration of hydronium. pH can also exceed 14.

Kyither Min 2K

For pH, the significant figures matter AFTER the decimal. So if the concentration of Hydronium ions is .0136 mol/L , 3 sig figs. The pH would be 1.866, 3 sig figs after the decimal.

Kyither Min 2K

The units should be in Kelvin as the universal gas constant, R is in Kelvin. To find convert from Celsius to Kelvin just add 273.15.

Kyither Min 2K

When analyzing the equilibrium constant equation, we can see that the concentration of products is over the concentration of reactants. Therefore, the bigger the number, the larger the ratio between products to reactants is, or the more product is compared to the reactants. So, when the equilibrium ...

Kyither Min 2K

For pure solids, you can't find the concentration because it is a solid. For liquids, typically the liquid will be a solvent and therefore, there's a lot of it. If the reaction takes place with some molecules of the solvent, the amount of molecules changed is so insignificant that you can regard it ...

Kyither Min 2K

On Dr.Lavelle's sig fig worksheet, he said to count the sig figs after the decimal for pH, so I suggest you go with that.

Kyither Min 2K

It is called bidentate because the oxalate is able to bind to the metal twice with it's two oxygens that have electron pairs to spare.

Kyither Min 2K

I may be wrong but i believe that the structure of SO2 and SO3 are like that because they have resonance and resonance makes a structure a lot stronger and stable so resonance is preferred!

Kyither Min 2K

A single bond will only have 1 sigma bond. The very first bond made is a sigma bond and each additional bond is a pi bond. I like to count the number of bonds and save one for sigma and the rest as pi. So amount of pi bonds are # of bonds - 1.

Kyither Min 2K

I think we will have to know common ligands such as ammine, chloro, and cyano.

Kyither Min 2K

Yes. With the AXE formula you can deduce what shape and bond angle the molecule will have based on charts and tables.

Kyither Min 2K

Order doesn't matter but some prefer writing it dsp3 since it shows that the d orbital is utilized however sp3d is in order of utilization.

Kyither Min 2K

Nitrogen can not have 5 bonds because it doesn't have a d-orbital. Only elements in Group 3 plus have d-orbitals they can utilize for more than 4 bonds.

Kyither Min 2K

Yes. The stronger the IMFs are the harder it is to break the forces holding the molecules together. To boil something is to turn that substance to liquid to gas and that requires breaking the forces therefore, it takes more energy to break the stronger IMFs. In this case, energy is in the form of he...

Kyither Min 2K

Dipole moments are formed when atoms don't "share" electrons fairly so the more electronegative atom would pull the electrons to their side creating a temporary charge shift, the dipole moment.

Kyither Min 2K

So AX3E2's steric number is 5 and so that shape would be trigonal bipyramidal but since you remove two atoms and have two lone pairs in it's place, the final shape would be t-shaped.

Kyither Min 2K

Sigma bonds are first because without sigma bonds, pi bonds wouldn't form. You can only have one sigma bond because the orbitals have to be the right spin and attraction to hybridize into sigma bonds and the pi are the other orbital hybridizations.

Kyither Min 2K

All molecules have in some way shape or form Van der Waals forces. These forces are typically weak but when there are many, it can be strong and prevalent.

Kyither Min 2K

Yes, tetrahedral molecules should have a bond angle of 109.5

Kyither Min 2K

Lone pairs matter! The steric number is the amount of lone pairs and bonds the central atom has and so the steric number might be the same for multiple molecules but the shape of the molecule could be very different depending on the amount of lone pairs the atom has. For example, H2O has a steric nu...

Kyither Min 2K

Elements after period 3 can have an expanded octet because of the additional d orbital they have. Typically, Phosphorus or Sulfur are the elements that do expand their octet.

Kyither Min 2K

Typically, you would choose the element that has the lowest ionization energy as the middle and in this case, it is oxygen. Also, Chlorine typically only forms one bond so it wouldn't make sense to have Chlorine in the middle.

Kyither Min 2K

It is when the atoms are closest to the formal charge of 0.

Kyither Min 2K

We could eventually remove the electrons from the d and f orbitals but if you notice the shell number for the d and f orbitals, they're either 1 or 2 shells before the s and p orbitals. When you remove an electron, you take from the outermost shell since they're the easiest to be removed therefore, ...

Kyither Min 2K

Ionization energy is how much energy is required to remove an electron but electonegativity is how attracted the atom is to gaining an electron. Most cases, the higher electronegativity the higher the ionization energy since they want to gain an electron, not lose an electron. Therefore, it'll be ha...

Kyither Min 2K

I think we probably will be using lines in the future since it's a faster way of representing larger molecules, but the Lewis Structure allows you to see resonance and lone pairs more clearly so you can later determine the shapes of the molecules.

Kyither Min 2K

Yes! I think using dimensional analysis is very important when solving problems like these. Make sure that the units cancel out in the end to get what you want and make sure you're using correct values for each.

Kyither Min 2K

the letter ml is used to denote the amount of subshells in an orbital. Typically, the amount of subshells in an orbital is from l,l-1..0..-l.

Kyither Min 2K

kg since the measurement of SI unit , Joules, is kgm^2/s^2 so we use kg

Kyither Min 2K

You'd typically will have to solve for molar mass which you can do by analyzing the molecule and seeing how many of each element there is, and referencing the periodic table, you can solve for molar mass.

Kyither Min 2K

So each element has different amount of varying orbital energy levels. Hydrogen's orbital energy levels are different from Oxygen's and when electrons transition from one orbital energy to another, depending on the element, the release of energy is different. The releases of energy are in the form o...

Kyither Min 2K

The threshold energy is the amount of energy required to bump an electron out of the metal plate that the light is hitting. It's the minimum amount of energy to rip the electron out of it's shell.

Kyither Min 2K

Constants do not affect significant figures since significant figures are a sense of how precise something is. Constants are known to be very precise and would have no affect on the final calculation for significant figures since it's already known to be precise.

Kyither Min 2K

It should add up to 100% since mass can not be created nor destroyed and what mass percent composition is stating is just how much the particular element weighs in the whole compound, or it is a percentage of the total mass and so percentages should always add up to 100%.

Kyither Min 2K

I think the best way to figure out limiting reagent for any amount of reagents is figuring out the amount of moles of each reagent. Then, using the coefficients of the balanced equation, figure out how many moles of the product each reagent will get you if the rest of the reagents were in excess. Fi...

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