CHEMISTRY COMMUNITY

Sophia Diaz - Dis 1B

Hi everyone! For test #2, I got both parts of #4 completely wrong. Can anyone explain to me how you are meant to solve the problem and what the answers are? For reference, I thought that the NO3- equation was the anode and the Zn2+ was the cathode which got me an Ecell of -1.56V. and my Cell diagram...

Sophia Diaz - Dis 1B

I think the reason why is because all of the values are technically already given to you since you can find the [H30+] through the pH, which is given, and the [HCO3] is given in the prompt. Because of this, you have all the numbers you need in order to find [CO2]. So I don't think its that an ICE ta...

Sophia Diaz - Dis 1B

In order to find the value of n, you need to have experimental data which will be given in a table the problem. First, you need to find 2 experiments where only one of the compounds is changing. For example, if [A] is 0.5 in experiment 1 and 1.0 in experiment 2 while [B] is 0.5 in both experiments 1...

Sophia Diaz - Dis 1B

per mole really just means per one mole of the product. So if something is 45 KJ per mole, it means that it requires 45 KJ for every one mole of the product. If there are multiple products, then each product will have its own KJ/mol amount. If there are multiple moles of a single product, then the E...

Sophia Diaz - Dis 1B

No, I don't think coefficients matter when your finding order.

Sophia Diaz - Dis 1B

For part c of this problem, it asks to find the value of K but it doesn't say which experiment to use. Does this mean that we can use any experiment we want to find the value of k? I noticed that in the solutions manual that they use several experiments and get a different value of k for each one, s...

Sophia Diaz - Dis 1B

In problem #3, part c asks to find the unique rate of the reaction, but I don't understand what the unique rate of reaction is. How are you meant to calculate it?

Thanks y'all!

Sophia Diaz - Dis 1B

Do you know where you found this info? Because I thought you weren't allowed to mix partial pressure and concentrations you use either/or. So if an equation is made up of completely compounds in their gas phase then you use partial pressure whereas if it is a combination of gas and other phases you ...

Sophia Diaz - Dis 1B

I understand the process in which we find the value of n, but I don't fully understand how we determine which experiment should be divided by another. For example, the in-class example had us dividing rate 2 by rate 1, but what if we divided rate 1 by rate 2. We would no longer get 2 as an answer an...

Sophia Diaz - Dis 1B

When you are given a table with the number of experiments, initial concentrations for compounds, and initial rates, you have to determine in which of the experiments the compound changes concentration. If you are dealing with two compounds, make sure that ONLY the one you are looking at changes in c...

Sophia Diaz - Dis 1B

How exactly does Gibbs Free Energy relate to whether or not a reaction is spontaneous? I understand it as: If \Delta G is negative the reaction is spontaneous and if \Delta G is positive the reaction is nonspontaneous. But when a reaction is "spontaneous" does that mean that the products a...

Sophia Diaz - Dis 1B

The best way I remember the difference is through the acronym OIL RIG. Basically, Oxidation is the loss of electrons and Reduction is the gain of electrons. When elements have an increase in charge, for example going from 2+ to 3+, it is losing electrons because the overall charge has become more po...

Sophia Diaz - Dis 1B

When we were balancing the Fe and Cu (Cathode and Anode, respectively) equations in the Hess's Law method in order to find the Ecell, why did we flip the Cu instead of the Fe equation? I know that we would get the same number but negative, but why is that a wrong answer and how are we supposed to kn...

Sophia Diaz - Dis 1B

From what I understand, those are the most common conductors so it would be good to know that when they show up in an equation and don't have any charge changes. However, I think you can usually tell if something is a conductor if is written in the balanced equation, but doesn't undergo any change i...

Sophia Diaz - Dis 1B

I think you do have to memorize Van't Hoff equation and how it relates to Gibbs Free Energy, but I don't think you have to memorize how to derive it as long as you know when to use the Van't Hoff equation. Usually, if there are homework problems on a topic, it fair game to show up on the test. So, i...

Sophia Diaz - Dis 1B

When it comes to work, you don't need to memorize the derivative/integral equations. We were only shown them in order to understand where they came from and how to solve for what is missing. When it comes to the rest of the work equations, most of them are shown on the equations worksheet when we ha...

Sophia Diaz - Dis 1B

I'm pretty sure that the sign of delta G determines how stable something is. So if delta G is greater than 0 (positive) it is generally less stable while if delta G is greater than 0 (negative) it is more stable. The reason why delta G relates to stability is that it has something to do with whether...

Sophia Diaz - Dis 1B

Hey y'all! So I'm having trouble understand what Gibbs Free Energy is and how it relates to enthalpy and entropy. I know what the equation is to solve it but why can you solve for \Delta G using \sum G (prod) - \sum G (react) if \Delta G, \Delta H, and \Delta S are all different? Thanks so much!

Sophia Diaz - Dis 1B

When we were discussing irreversible processes on Wednesday, we were shown two graphs of an irreversible and reversible process where the reversible had a small negative w (work) and the other had a larger negative w. I'm kind of confused if a larger negative w mean there is more or less work being ...

Sophia Diaz - Dis 1B

I'm pretty sure as long as the units match you should be good.
So if the units you need is J in order to cancel out the other J, but it's given to you in KJ, but convert KJ to J so that they all cancel out.

Sophia Diaz - Dis 1B

I don't fully understand when and where we are supposed to use these " \int ' equations. Are we actually supposed to use them to solve problems or did we just go over them in order to show where the other equations came from? Also how do you know how these equations change depending on what is ...

Sophia Diaz - Dis 1B

In class when we were discussing molecules, possible positions, and residual entropy, we did a calculation with the equation: S = KblnW.
In the equation, Kb was equal to 1.381 x 10^-23 J/K.

Where did we get the value for Kb and what exactly IS Kb?

Thanks, y'all!

Sophia Diaz - Dis 1B

You can usually tell which constant to use depending on the units that are given in the equation or by what you are looking. Pay attention to the units of the values they give you, what you are solving for, and the units of the R constant. The units SHOULD always cancel out meaning that you use the ...

Sophia Diaz - Dis 1B

I don't understand how the equation: w = -P \Delta V is found from the integral equation with the summation of steps (the one with the derivative). Can someone please explain where w = -P \Delta V comes from? Follow up question: how does w = -P \Delta V relate to the the equation \Delta U = \Delta H...

Sophia Diaz - Dis 1B

So I'm still unclear as to what the difference between heat and energy/enthalpy is. I always sort of thought they were the same thing since adding heat to something increases energy. So by adding heat aren't you adding energy? Why aren't the terms interchangeable?

Sophia Diaz - Dis 1B

You can determine which bonds are broken and formed when you look at the molecules in a reaction equation. When molecules have changed, pay attention to what those molecules would look like and which bonds are no longer present or which ones have formed. It may help to draw out rough structures for ...

Sophia Diaz - Dis 1B

The question is: Which molecular substance do you expect to have the higher molar heat capacity, NO or NO2? Why? I don't fully understand what the questions means by "heat capacity" or how I'm supposed to determine which substances will have a higher one. Could someone explain what this qu...

Sophia Diaz - Dis 1B

For what I understand, when you use bond enthalpies, you use them for the bonds that are being used in the reaction. So for the reactants side, there is a C=C bond that breaks into a C-C bond when it forms into CH3-CH2Br. There is no C=C bond on the products side and there is no C-C bond on the reac...

Sophia Diaz - Dis 1B

In class we did an example with NO2 formation: N2 + O2 --> 2NO 2NO + O2 --> 2NO2 ---------------------- N2 + 2O2 --> 2NO2 The way we got the third and final reaction was by adding the first two and the 2NO's "canceled out." I don't really understand how the 2NO's canceled out but the O2's ...

Sophia Diaz - Dis 1B

When I was looking in the solutions manual to check my answer, it turns out I did this problem wrong. Instead of using the equation: H2SO4 + H2O --> H3O + HSO4 you were supposed to use the equation: HSO4 + H2O --> H3O + SO4 How were you supposed to know that H2SO4 dissociates twice? When will I know...

Sophia Diaz - Dis 1B

I'm not really sure if I did the problem correctly but this is how I thought about it: I'm pretty sure the way you figure out the coefficients is based on the looking at the y-axis. For example, A was at 30 and went down to 15, B and C started at 0 and went up to 5 and 10, respectively. This means t...

Sophia Diaz - Dis 1B

Because most of the reactions we deal with have molecules in an aqueous solution it is already implied that all the molecule are in water, so water is written in the equation. Also the way the equation is written in terms of products, its more clear to have water on the left side of the equation so ...

Sophia Diaz - Dis 1B

R is a constant that I'm pretty sure will be given to you on an equations list when we take exams. You just have to be aware of which R you use since it changes depending on what you're using. Meaning, R = 0.08206 when we are using Liters and atm (which is what we are doing now), but R = 8.314 when ...

Sophia Diaz - Dis 1B

I don't really understand when we have to use this equation. When we are solving for Kp don't we use solve with [Products]/{Reactants]? When are we supposed to use the entire equation of PV=nRT?

Sophia Diaz - Dis 1B

In homework problem 11.13 (6th edition): Write the reaction quotient for: P4210(s) + 16 H2O (l) --> 4H3PO4(aq) + 10 H2S (aq) The answer is: Q = (H3PO4)^4 (H2S)^10 I don't think I understand why we don't include the molecules in liquid or solid form. Why do we only include molecules in a gas or aqueo...

Sophia Diaz - Dis 1B

I don't think I understand how lone pairs change bond angles. Let's say there was a tetrahedral molecule. I know that those bond angles are 109.5, but when lone pairs start getting introduced, do the bond angles increase or decrease and why? Does this apply to all molecules that get lone pairs intro...

Sophia Diaz - Dis 1B

In a science lab, you created a stock solution of 1.50 M Na2O. A) How many milliliters of this stock solution would you need to make 210 mL of a .550 M Na2O solution? I know that to answer this question I just need to use the formula M1V1 = M2V2 and I'll get the answer 77mL B) What is the pH of your...

Sophia Diaz - Dis 1B

For #25 on the "French Toast" practice sheet, the question is: What is the oxidation state of [Pt(Cl)2(NH3)2]? The answer is 2, but when I do the calculations I only get 0. What I'm doing: M + (# of Cl)(Cl charge) + (# of NH3)(charge of NH3) = 0 So: M + -2 + 2 = 0 M + 0 = 0 M = 0, thus the...

Sophia Diaz - Dis 1B

I was looking at the practice problem from the "French Toast" worksheet and number #24 asks whether or not a molecule is a chelating ligand. I tried to look it up but I don't understand the explanation. What exactly is a chelating ligand and how do you know when a molecule is a chelating l...

Sophia Diaz - Dis 1B

When something is referred to as "less acidic" does that mean that it also a weaker acid and vise versa? How does the strength of acids refer to pKA because I don't really understand how it reflects acidic levels and strength?

Sophia Diaz - Dis 1B

I don't really understand a lot about ligands so I have a couple questions about them.

When there is a large organic compound does every single lone pair count as a ligand? Are ligand only lone pairs or can they be something else? Also, when are lone pairs NOT ligands?

Sophia Diaz - Dis 1B

In section, we were learning about how to determine the polarity of certain molecules. My TA kept saying something along the lines you want to find the "sum of dipole moment vectors," but I don't really understand what these are and how you are supposed to calculate them?

Thanks!

Sophia Diaz - Dis 1B

I know that there a few molecules that have a "bent" or "angled" shape such as H2O or ClO2. But since they only have 2 atoms attached in each case wouldn't they be linear? How are you supposed to know when a molecule is bent rather than just being linear?

Sophia Diaz - Dis 1B

Is there a difference between the terms that end with "-dral" and "-dron" or are they the same thing? Can you use them interchangeably?
For example the terms octahedral and octahedron? If they're different when do I use one over the other?

Thanks!

Sophia Diaz - Dis 1B

From what we learned in lexture today it looks like I was only partially correct. Hybridizations happens a lot more often then I thought, but it still only happens based on regions of density and shape. So you would use shape and density to determine when something hybridizes. To answer the question...

Sophia Diaz - Dis 1B

I'm pretty sure there are no specific exceptions we need to know, but you do need to know how angles will change depending on things like the number of electron densities and lone pairs. So for example, if 2 molecules have 4 areas of electron densities but one has 4 atoms and another has 3 atoms and...

Sophia Diaz - Dis 1B

In the case of bonds, it has to do with the way atoms attract each other. Since the bonds are shorter, the atoms attract each other with more force and are harder to break. But when the bond is longer, the attraction is not as strong and its easier to pull the two atoms away from one another. Think ...

Sophia Diaz - Dis 1B

I think it has something to do with the fact that hybridization does not always happen. So in the case of carbon, hybridization only happens because that what the shape and bonds require. But not every ground state element will have hybridization because it doesn't need Hybridization. For example, H...

Sophia Diaz - Dis 1B

He may have used both terms, but I think he is referring to the same thing. So, in this case, both bond angles and just "angles" are just the angles that are caused by atoms repelling each other. The atoms must be separated as symmetrical as possible which is why the angles get smaller as ...

Sophia Diaz - Dis 1B

In class, there was a graph showing the relationship between electronegativity and ionic/covalent bonds. On the graph, I noticed that CsF had less ionic properties than LiF, but Cs had a value of 0.79, Li had 1.0, and F had 4.0. Doesn't that mean that CsF should be more ionic than LiF since the diff...

Sophia Diaz - Dis 1B

Put these in order of increasing polarizability: The answer is O-2, N-3, Cl-, Br-, but I'm not sure how you would solve this. Apparently, O and N are in that order because of smaller electronegativity and Cl and Br have more shells, but I don't understand why that is. Why does size effect polarizabi...

Sophia Diaz - Dis 1B

Arrange the following in order of increasing polarizing power: Rb+, Be2+, and Sr+2 The answer to this question was Rb+, Sr+2, Be+2 I don't understand how this is the answer since two of the elements have the same charge. How do you decide which one has more polarizing power? Isn't Be larger than Sr ...

Sophia Diaz - Dis 1B

I now that in class it was mentioned that if a compound/molecule has a lone pair than it is an acid, but I don't understand why this is? Why does a lone pair mean that it's an acid? Does that mean if there are no lone pairs it is base?

Sophia Diaz - Dis 1B

How exactly would these bonds happen though? If they both come from the same atom wouldn't that atom want to hold onto the electrons as much as possible? Does it have something to do with periodic trends?

Sophia Diaz - Dis 1B

When describing a lot of trends I notice that the idea of electron repulsion comes up a lot, but I don't understand how it really relates to everything. How does electron repulsion in different atoms affect trends? For example, how does electron repulsion cause the size of the atom to be smaller? Do...

Sophia Diaz - Dis 1B

I know that only certain elements can have expanded octets, but I wanted to know if these certain elements can have more than 10 electrons? Since these elements can have 10 electrons due to them having a d orbital, does these mean that certain elements can have 14 if they have an f orbital? Will we ...

Sophia Diaz - Dis 1B

In a review session, there was a question asking which of the following was the largest in terms of atomic radii? Ca+2, Ar, or Cl-? Apparently, the answer is Cl- since it has the least number of protons. But I don't understand why? Why does the number of protons have anything to do with the atomic r...

Sophia Diaz - Dis 1B

Hi guys! So I remember in class going over isoelectric atoms, but I don't really get why they are not the same size? If they have the same amount of electrons, doesn't that mean they should all be relativity the same size?

Sophia Diaz - Dis 1B

I've noticed the word "orbitals" used in a few different ways and I'm kind of confused on what is considered an "orbital." I know that we called "n" values orbitals, such as s, p, d, and f orbitals, but then I see that sometimes values of "l" are also called o...

Sophia Diaz - Dis 1B

Follow up question: I don't understand where the electrons are coming from when you write the correct configurations. For example: If Cu is [Ar]3d^9 4s^1, what was the original configuration? Is it [Ar]3d^8 4s^2 or [Ar]3d^10? Also, if 3d orbitals are supposed to fill up before 4s orbitals, why would...

Sophia Diaz - Dis 1B

In a recent suspense film, two secret agents must penetrate a criminal's stronghold monitored by a lithium photomultiplier cell that is continuously bathed in light from a laser. If the beam of light is broken, an alarm sounds. The agents want to use a handheld laser to illuminate the cell while the...

Sophia Diaz - Dis 1B

Lines in the Balmer Series of the hydrogen spectrum are observed at 656.3, 486.1, 434.0, and 410.2 nm. What is the wavelength of the next line in the series?

I have no idea where to start with this problem. Is there an equation or something that I can use to find this out?

Sophia Diaz - Dis 1B

a) If an absorption occurs in the infrared spectrum at 3600cm^-1, what is the frequency of radiation that corresponds to that absorption? Use the equation: V = CE to get V = 1.08 x 10^14 Hz b) What is the energy in Joules of that absorption? Use the equation: E = hv to get E = 7.16 x 10^-20 J c) How...

Sophia Diaz - Dis 1B

Just to make sure I did the problem correctly, I got the same number for both of the parts. Did I use too little sig figs (I used 3) or is this the same thing that you guys got? And if they are the same number does that mean that there's 0% difference between them? Thanks!

Sophia Diaz - Dis 1B

Just a really quick follow up question. When I was looking up at solutions online in order to make sure that I was getting the correct answer I noticed that some solutions said the MPH meant meters per hour while others said it was miles per hour. I was pretty sure MPH was miles per hour, but I just...

Sophia Diaz - Dis 1B

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/s a) What is the wavelength of the ejected electron? b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 x 10^16 Hz How much energy is required to ...

Sophia Diaz - Dis 1B

I know that in lecture we went over why high intensity doesn't always mean high energy and that there were 2 different models used to explain this. However, I don't understand this concept in terms of the 2 different models and why the wave model doesn't reflect the actual energy of a light. Could s...

Sophia Diaz - Dis 1B

When you're finding the mass amount of product a limiting reactant can make I know you're supposed to use the stoichiometric ratios from the balanced equation. The example we did in class was easy since all the ratios were 1:1. But what happens if the ratios are some different like 1:2 or 3:4? For e...

Sophia Diaz - Dis 1B

Hey guys! I recently got my Week 1 Homework back and lost points for writing down the wrong problems. I checked my textbook (the 6th edition) and it turns out I DIDN'T do the wrong problems. When I asked my TA, they said the problems are misnumbered because I'm using the wrong version. They said we ...

Sophia Diaz - Dis 1B

One of the questions I keep running into is: Can the mass of the products of an equation be more than the mass of the reactants? I can see the answer being yes because maybe in certain reactions surrounding elements during the experiment like oxygen may affect the reaction, but I don't know if that ...

Sophia Diaz - Dis 1B

During lecture, we learned that a method of finding the limiting reactant is by using ratios and the amounts of moles. For example: Trying to Find the Limiting Reactant when 100g of H20 reacts with 100g of CaC2 If the balanced equation is: CaC2 + 2H2O ---> Ca(OH)2 + C2H2 Then you can calculate the n...

Sophia Diaz - Dis 1B

During a summer camping weekend, 4 moles of butane (C4H10) gas were used for cooking. Choose the right balanced equation for the combustion of 4 moles of butane gas. What is the net number of moles of gas produced? A. 4 C4H10(g) + 26 O2(g) ----> 16 CO2(g) + 20 H2O(g); 6 B. 4 C4H10(g) + 26 O2(g) ----...

Sophia Diaz - Dis 1B

I know that one of the steps in finding an empirical/molecular formula is dividing by the smallest number after you find the number of moles for each element. However, I don't understand WHY we have to take this step. What's the mathematical reason for dividing by the smallest number?

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