CHEMISTRY COMMUNITY

Nicolette_Canlian_2L

I don't believe there's a gain in using one over the other. It just depends on how you isolate the variables.

Nicolette_Canlian_2L

How do we calculate a rate law if we are given the rate of disappearance instead of the rate of formation?

Nicolette_Canlian_2L

the pre-equilibrium approach is a simpler way to get to the same solution with less complication.

Nicolette_Canlian_2L

ChathuriGunasekera1D wrote:I know that I use the word "unique" to know if I have to use (-1/a)(dR/dt)

How do we apply the unique reaction rate?

Nicolette_Canlian_2L

Since A is the reactant being used, its graph will be decreasing to a certain level and then stabilizes because equilibrium is reached. Since A has a coefficient of 2, the product B will be increasing/forming at a rate half of it. Product C will be forming at a rate triple the rate of A. Referencing...

Nicolette_Canlian_2L

as long as the ratio of the the rates correspond to the concentrations that come along with them.

Nicolette_Canlian_2L

since this is a galvanic cell, we know that the reaction occurs spontaneously and energy is not required to start the reaction. You might be mixing this up with the concept of electrolytic cells brought up in lecture today because those require another source of energy for redox reactions to take pl...

Nicolette_Canlian_2L

I believe that the solids must be placed on the outer part of the cell diagrams and the aqueous solutions are right next to the salt bridge. In regards to the liquid, I'm not too sure if it follows the same rules as solids.

Nicolette_Canlian_2L

then is standard reduction potential equal to 0?

Nicolette_Canlian_2L

You might be thinking about the difference between an electrolytic cell and galvanic cell. An electrolytic cell is one in which delta G is positive and the standard cell potential is negative. In a galvanic cell, delta G is negative and the standard cell potential is positive. galvanic=spontaneous a...

Nicolette_Canlian_2L

the metal conductor is always added to the outer part of the cell diagram.

Nicolette_Canlian_2L

I'm having trouble with this one as well. What is the relationship between gibbs free energy and stability? Do we have to consider the other thermodynamic terms as well?

Nicolette_Canlian_2L

I believe they have the same function, but the shapes of them are what differ.

Nicolette_Canlian_2L

You would only use bar if the question were to ask, for example, the pressure of the gas at equilibrium.

Nicolette_Canlian_2L

additional energy is required to change water from its boiling point to steam. Extra heat will cause the boiled water to reach vapor and burn more.

Nicolette_Canlian_2L

certain diatomic molecules, like CO2 and H2O are in the most stable forms.

Nicolette_Canlian_2L

rather than just using the ideal gas constant, you use 5/2R and 3/2R as the constants depending on whether volume or pressure is constant.

Nicolette_Canlian_2L

I think we're going to cover this further in class, but it seems to be related to the linearity of a molecule.

Nicolette_Canlian_2L

is there a relationship between degeneracy and entropy?

Nicolette_Canlian_2L

I was stuck on the same question. So we have to convert the given mass of the krypton gas into moles and work from there?

Nicolette_Canlian_2L

I'm not entirely sure, but I'm assuming since there aren't any external factors affecting the course of the reaction, there won't be any so-called errors in the experiment.

Nicolette_Canlian_2L

A closed system is also sealed, but the transfer of energy is what is observed. When comparing open and closed systems, we observe changes in matter.

Nicolette_Canlian_2L

Could you find the difference of the number of bonds broken and the total number of bonds formed? I remember learning it this way in high school, but I'm not too sure.

Nicolette_Canlian_2L

Since the reaction requires heat, decreasing the temp would make it difficult for the reaction to take place. For this reason, the reaction shifts towards the reactants to form more heat necessary to carry out the reaction.

Nicolette_Canlian_2L

Does this reaction only have one product in either the gaseous or aqueous state?

Nicolette_Canlian_2L

I have the same question. Does it have anything to do with the volume increasing since liquid water is placed into the reaction? Would this therefore decrease the pressure of the system? I don't understand how water at its liquid state would be incorporated into the equilibrium constant.

Nicolette_Canlian_2L

It can be used to solve for any of the variables in the equation. Temperature is constant, so it'll be used to solve for the other conditions.

Nicolette_Canlian_2L

The conjugate acid to the base will be the molecule that has gained a proton. The conjugate base to an acid will be the molecule that loses a proton.
HCOOH + H2O----HCOO[-] + H3O+
HCOOH is the acid and HCOO[-] is the conjugate base.

Nicolette_Canlian_2L

you can use a quadratic or maybe even a cubic function if it comes down to that. Checking the percent ionization does save time though.

Nicolette_Canlian_2L

in the 7th edition 5I.13, the questions asks us to find the equilibrium composition of of the mixtures when 2.0mmol Cl2 and 2.0mmol F2 are placed in different 2.0L vessels at 1000. K. Part C asks which is more thermodynamically stable. How do we determine the stability? Is it based on the equilibriu...

Nicolette_Canlian_2L

Aurbal Popal wrote:Wait do we just ignore water as a liquid if we are doing partial pressures (Kp) or does this apply when we do Kc as well?

I believe so, since we only include gases and aqueous solutions in K expressions.

Nicolette_Canlian_2L

I second this!! Also, how did you figure out part a and b? How do we determine equilibrium by looking at the molecules?

Nicolette_Canlian_2L

what does P^o represent?

Nicolette_Canlian_2L

I'm not sure how to approach this problem. In the 7th edition, it is part of the self test 3B.2A. A rigid oxygen tank stored outside a building has a pressure of 20.00atm at 6:00am, when the temp is 10 degrees celsius. What will be the pressure in the tank at 6:00pm, when the temp is 30. degrees cel...

Nicolette_Canlian_2L

You can also determine this based on the atomic radius. Since I has a larger atomic radius than Cl, it is easier for the I atom to release H+ than it is for Cl because of the looser pull of the electrons towards the central atom.

Nicolette_Canlian_2L

I believe its geometry comes about because of the lone pair on the iodine. If it were trigonal bipyramidal, there would not be any lone pairs on the central atom.

Nicolette_Canlian_2L

Are the sig fig rules different when applied to pH, then?

Nicolette_Canlian_2L

I recommend making flashcards and referencing the sheet Dr.Lavelle has posted on the class website.

Nicolette_Canlian_2L

When determining dipole moments, consider the electronegativity of the atoms in the molecule and check for any lone pairs on the central atom.

Nicolette_Canlian_2L

In the case of the sulfate ion, sulfur and the oxygens that are double-bonded to the sulfur will have formal charges of zero. The oxygens that are single-bonded to the sulfur will each have a formal charge of negative one, adding up to negative two. This contributes to the sulfate ion's charge of ne...

Nicolette_Canlian_2L

Lone pairs cause repulsion between the the atoms bonded to the central atom. They create a smaller bond angle between the atoms because the atoms will be pushed down.

Nicolette_Canlian_2L

You can check the number of lone pairs on the central atom and try to determine the shape of the molecule to find the overall dipole moment (if it exists).

Nicolette_Canlian_2L

You want to check the formal charges of the atoms in the molecule, so that explains the bonding of xenon and fluorine in this example.

Nicolette_Canlian_2L

So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule? Under my current understanding, I believe any element in the first three groups don't have to meet the octet rule of maximum 8 electrons, it can exceed the octet rule since it has access to th...

Nicolette_Canlian_2L

Does it only apply to gases?

Nicolette_Canlian_2L

So is any element in the first 3 groups without a d-orbital in its shell unable to fulfill the octet rule?

Nicolette_Canlian_2L

does this question apply to the example we did in lecture in which XeF4 was defined as having octahedral geometry and square planar shape? I was confused by this.

Nicolette_Canlian_2L

^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs. So does this mean GC base pairs have stronger bonds than AT base pairs? Yes, because G-C base pairs have three hydrogen bonds rather than two...

Nicolette_Canlian_2L

is the polarity determined only by the electronegativity of an atom, or are there other factors that contribute?

Nicolette_Canlian_2L

Alexa_Henrie_3B wrote:^Exactly. Higher melting points indicate more stability so this explains the example given in class: GC base pairs in DNA are more stable than AT base pairs.

So does this mean GC base pairs have stronger bonds than AT base pairs?

Nicolette_Canlian_2L

I am confused on this lewis structure in general. Is the octet rule for chlorine not supposed to be fulfilled?

Nicolette_Canlian_2L

I think there might also be a chart to help memorize the different shapes of molecules. It should list the number of bonded and lone pairs, which determine the molecular shape.

Nicolette_Canlian_2L

What exactly is a dipole moment? I know it was to do with charges, but is there a deeper explanation?

Nicolette_Canlian_2L

why is nitrogen more electronegative than oxygen? Does it relate to the number of electrons filling the d-orbital?

Nicolette_Canlian_2L

I don't understand where the 124 is coming from. Is there a calculation that needs to be done to come to this bond length value?

Nicolette_Canlian_2L

The periodic trends of atomic radius follow for both ionic and covalent radii also. The bonding types might be different, but the ionization energy will still be greater for an atom further across a period and smaller for an atom lower in a group.

Nicolette_Canlian_2L

I believe that the rule applies to objects that are smaller than 10^-18. I am not confident on this though, so if anyone else knows, that would be helpful!

Nicolette_Canlian_2L

This will also relate to sigma and pi bonds, which we will learn about later. It will make more sense when applied to these concepts.

Nicolette_Canlian_2L

Yukta Italia 3I wrote:Why are electrons that are further away from the nucleus easier to remove?

The inner electrons shield the other electrons, causing a decrease in the effective nuclear charge. This allows for an easier removal of a valence electron.

Nicolette_Canlian_2L

why is the energy level of 102.6 nm 1? This is what i don't understand. Even when I see pictures of the spectroscopy with the Lyman series, I notice that 102.6 is one of the values next to a line, but I'm not sure how to identify that it is n=1 . I just realized that we have to use an equation to s...

Nicolette_Canlian_2L

I believe it should still be 40 points like the last one.

Nicolette_Canlian_2L

exactly what do all the quantum numbers represent?

Nicolette_Canlian_2L

why is the energy level of 102.6 nm 1?

Nicolette_Canlian_2L

what is the relationship between energy and frequency?

Nicolette_Canlian_2L

is there a certain constant that comes along with the size of a photon?

Nicolette_Canlian_2L

Does Avogadro's number include units, or do we use the number alone?

Nicolette_Canlian_2L

Do we have to first convert the grams of each compound into moles and then find the mass of the individual elements from there?

Nicolette_Canlian_2L

and just another sig fig rule is that if the decimal is 0.405, you would round your answer to 0.400 when needing 3 sig figs. When the last digit ends in five, would want to round the digit prior to it to the nearest even number.

Nicolette_Canlian_2L

Just by looking at the equation of a chemical reaction, how can we determine which reactant is limiting?

Nicolette_Canlian_2L

Sometimes the problem won't directly give you the initial molarity, so you might have to convert the given mass of solute to moles. Then divide by the volume of the solvent to find the initial molarity.

Nicolette_Canlian_2L

I first found the molar mass of the (OH)2, and then I subtracted this value from the given molar mass. This will give you the molar mass of the metal. Then, you must add the molar mass of the metal to the the molar mass of the sulfide ion to find the mass of the sulfide of this metal. Let me know if...

Nicolette_Canlian_2L

Can we leave our answer in pm, or do we have to convert it to km?

Nicolette_Canlian_2L

The method I used to solve part a is by multiplying the mass of each with its correlating percentage of abundance and then added these products together.
m=0.0742(9.988x10^-24g)+0.9258(1.165x10^-23g)
m=1.153x10^-23g
Then I multiplied the sum of those two with Avogadro's constant and got 6.94g/mol

Nicolette_Canlian_2L

How do you go about solving part b? Do I use the same equation I used for part A?

Nicolette_Canlian_2L

I believe molecular unit refers to the mass of an entire molecular compound and formula unit refers to the mass of an ionic compound. These are defined on page F42 in the 7th edition book.

Nicolette_Canlian_2L

I am confused on this problem as well. I'm unsure of what the initial and final volumes are. I used the 15L as the initial volume and when it came to the final volume I was not sure whether to use the 0.02L or 0.250L.

Nicolette_Canlian_2L

The method I use to solve limiting reactant problems is by converting the reactants' mass into moles. I don't think this is impossible because once you have converted the reactants into moles, you compare the two. The reactant with less moles is the limiting reactant. I believe you can solve these k...

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