CHEMISTRY COMMUNITY

Rhea Jain 2I

Hello! Here's a short summary:

1st order: graph of ln[A] vs. time is a negative linear slope
2nd order: graph of 1/[A] vs. time is a positive linear slope
0 order: graph of [A] vs. time is a negative linear slope

Hope this helps!

Rhea Jain 2I

Hello! There are two types of rate laws: differential and integrated. The differential rate law tells you how the rate of a reaction changes depending on the concentration and of reactants, specifically the activation energy. The integrated rate law tells you how the concentration of reactants chang...

Rhea Jain 2I

Unfortunately, in this case, you'll have to calculate it yourself using the equations and methods we've learned in class. There was a bit about this in the textbook too in Focus 6, I recommend taking a look!

Rhea Jain 2I

Hi! Eºcell is at standard conditions, which means at 1 atm and 298K and cannot change from that value. Ecell can change based on temperature, however.

Rhea Jain 2I

Hello! In a closed system, the matter within the system is constant but energy is allowed to be transferred from system to surroundings and vice versa. This is different from an isolated system, where neither matter nor energy transfer between a system and its surroundings are allowed.

Rhea Jain 2I

The Arrhenius equation is sometimes expressed as k = Ae-E/RT where k is the rate of chemical reaction, A is a constant depending on the chemicals involved, E is the activation energy, R is the universal gas constant, and T is the temperature.

Rhea Jain 2I

Hi! You are correct that Le Chatelier's Principle outlines that reactions will shift their position of equilibrium to counter disturbances. However, Le Chatelier's principle also tells us that increasing the temperature of a system causes the position of the equilibrium to shift to use up some of th...

Rhea Jain 2I

Hello! The change in Gibbs free energy for an electrochemical cell can be related to the cell potential because of the equation ΔG = -nFE. If after calculating all your necessary values you get a negative ΔG value, the reaction is spontaneous. Since F is a constant and n will always be positive, tha...

Rhea Jain 2I

What exactly are you referring to for your question about positive and negative? Regardless, here's some steps to help outline and an example (btw, I call it a RICE table because I like to write the reaction at the top because then it's easier to fill each line under each component of the reaction):...

Rhea Jain 2I

Hi! Basically, the addition of an inert gas at constant volume to the equilibrium mixture does not affect the position because when an inert gas is added to the equilibrium system at constant volume, then the total pressure will increase. However, the concentration of reactants and products (ratio o...

Rhea Jain 2I

Hi! For a reversible process, the increase and decrease in entropy of the system equals the decrease and increase in entropy of the surroundings, so that the change in entropy of the combination of the system and surroundings is zero. I hope that helps!

Rhea Jain 2I

105736938 AADL wrote:Do all the posts have to be related to chem to receive points, or as long as it is 30, were fine?

As long as it's 30 you're fine, but I'm not sure how they will determine the extra credit points. Maybe they'll go through our individual posts?

Rhea Jain 2I

Dudeeee one of the lectures Lavelle whipped out Hazey by Glass Animals and I've never been more excited. Glass Animals is amazing!!!

Rhea Jain 2I

I cannot stress enough that practice problems are downright the BEST way to prepare for the 14 series exams, especially Lavelle. He recommends specific textbook problems for a reason. I always do them and have repeatedly seen similar or identical problems on exams. Also, go through a few Achieve pro...

Rhea Jain 2I

Any professor for 14A assumes you have prior knowledge and will very very briefly review the basics, but not much, as they don't have much time to teach new material. Therefore, if you know you struggled or are rusty on high school chemistry material, I highly recommend using popular academic YouTub...

Rhea Jain 2I

I think we only reviewed zero, first, and second in class!

Rhea Jain 2I

An anode is the species or half-reaction that loses electrons and are oxidized. A cathode is the species or half-reaction that gains electrons and are reduced.

Rhea Jain 2I

Here are some outlined steps: 1. identify what is being oxidized in the reaction and what is being reduced 2. write two unbalanced half-reaction equations, one for oxidation and one for reduction 3. balance all the elements in the half-reactions EXCEPT H and O 4. for an acidic solution, balance O by...

Rhea Jain 2I

Never trust atoms, they make up everything.

Rhea Jain 2I

Anyone know any jokes about sodium? Na...

Rhea Jain 2I

Carbon and hydrogen went on a date. I heard they really bonded <3

Rhea Jain 2I

Why should you go drinking with neutrons? Because when you do, there's no charge $$$

Rhea Jain 2I

Old chemists never die, they just stop reacting!

Rhea Jain 2I

Dear Dr. Lavelle, After taking 14A with you, I knew that there is no one I would rather go through the 14 series with. Your organization and obvious care for your students is so comforting, as it's clear you really want your students to learn and feel confident about their knowledge in chemistry. I ...

Rhea Jain 2I

Also, I have a little charm I've had for a few year that I take to every exam I've been anxious about. I keep it in my pocket and play with it whenever I feel overwhelmed during the exam. I took it to my ACT, and it really helped me ground myself and maximize my time. I got a really good score, and ...

Rhea Jain 2I

For me, it's important to remind myself that the result of this exam does not define me and will not determine my entire future. As long as I've worked hard to the best of my ability, I can go in confident knowing I'll be satisfied with whatever the result is. I know this is easier said than done, b...

Rhea Jain 2I

The question states it is an acidic solution, which implies the use of H+ and not OH-, which are reserved for basic solutions.

Rhea Jain 2I

The oxidation number is 0 because O3 is in its neutral form. I know it can be confusing because O2 is also considered a natural form, this may require some memorization. I suggest looking up common neutral atoms and memorizing them, just to be safe!

Rhea Jain 2I

A single line | distinguished phases, while a double line || represents the salt bridge or the "arrow" of the reaction. If two reactants or two products are the same phase on the same side of a reaction, they'll be separated by a comma rather than a |.

Rhea Jain 2I

When doing these problems, I remind myself that O and H are to be dealt with separately, and to look at what's left in the molecules from there. Whatever is similar between the reactants and the products is what you're going to look at for oxidation numbers. I know that wasn't a very scientific answ...

Rhea Jain 2I

I can totally reiterate this, Vivek was one of my favorite UA sessions to go to because of his patience and thoroughness. Thanks!

Rhea Jain 2I

Evaluate the unknown quantity in each of the following cells: (a) Pt(s)|H2(g, 1.0 bar)|H+(pH = ?)||Cl−(aq, 1.0 mol⋅L−1)|Hg2Cl2(s)|Hg(l), Ecell = +0.33 V. My final balanced equation was Hg2Cl2 + H2 → 2Cl- + 2H+ + 2Hg When plugging all the values into the Nernst equation on the answer key, I don't kno...

Rhea Jain 2I

Predict the standard potential of each of the following galvanic cells: (a) Pt(s)|Cr3+(aq),Cr2+(aq)||Cu2+(aq)|Cu(s) For this question, the answer shows both half-reactions written like reductions as follows: Cu2+(aq) + 2e- → Cu(s) E°(cathode) = +0.34V Cr3+(aq) + e- → Cr2+(aq) E°(anode) = -0.41V In o...

Rhea Jain 2I

Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify the oxidizing agent and reducing agent in each reaction. (d) Reaction of chlorine in water: Cl2(g) → HClO(aq) + Cl2(g) How would you go about do...

Rhea Jain 2I

The following redox reaction is used in acidic solution in the Breathalyzer test to determine the level of alcohol in blood: H+(aq) + Cr2O72−(aq) + C2H5OH(aq) → Cr3+(aq) + C2H4O(aq) + H2O(l) Identify the elements undergoing oxidation or reduction and indicate their initial and final oxidation number...

Rhea Jain 2I

How do you count the number of different orientations in a diagram like this:

Rhea Jain 2I

Use data in Table 4C.1 or Appendix 2A to calculate the entropy change for (a) the freezing of 1.00 mol H2O(l) at 0.00 °C This is what I did: deltaS = (1.00)(6010)/273 = ~22.0 The answer key shows -22.0 because the deltaH fusion of water is plugged in as negative. Why is the deltaH fusion of water ne...

Rhea Jain 2I

A human body generates heat at the rate of about 100. W (1W = 1J⋅s−1). (a) At what rate does your body heat generate entropy in your surroundings, taken to be at 20. °C? Here is what I did: deltaS = (-100)/(20+273) = ~ -0.34 The answer is positive 0.34, but why is that if the 100. W had to be negati...

Rhea Jain 2I

(a) Calculate the heat that must be supplied to a copper kettle of mass 400.0 g containing 300.0 g of water to raise its temperature from 20.0°C to the boiling point of water, 100.0°C. (b) What percentage of the heat is used to raise the temperature of the water? Can someone help me with this proble...

Rhea Jain 2I

What do you do when it doesn't show up in the table? Like HCl?

Rhea Jain 2I

What did you plug in for the dilution equation?

Rhea Jain 2I

A student added solid Na2O to a volumetric flask of volume 200.0 mL, which was then filled with water, resulting in 200.0 mL of NaOH solution. Then 5.00 mL of the solution was transferred to another volumetric flask and diluted to 500.0 mL. The pH of the diluted solution is 13.25. (a) What is the mo...

Rhea Jain 2I

Calculate the pH and pOH of each of the following aqueous solutions of a strong acid or base: (d) 2.00 mL of 0.175M KOH(aq) after dilution to 0.500 L (f) 75.0 mL of 3.5×10−4 M HBr(aq) after dilution to 0.500 L How do you solve these problems in cases of dilution? I tried using the conc1/vol1 = conc2...

Rhea Jain 2I

A reaction vessel of volume 0.500 L at 700. K contains 1.20 mmol SO2(g), 0.50 mmol O2(g), and 0.10 mmol SO3(g). At 700. K, Kc=1.7×10^6 for the equilibrium 2 SO2(g)+O2(g)⇌2 SO3(g). (a) Calculate the reaction quotient Qc. (b) Will more SO3(g) tend to form? I converted mmol to mol for all three substan...

Rhea Jain 2I

Can someone help me solve this problem? I'm not sure what I'm doing wrong. 30. A mixture of 2.5 moles H2O and 100 g of C are placed in a 50 L container and allowed to come to equilibrium subject to the following reaction: C(s) + H2O (g) ⇌ CO (g) + H2 (g). The equilibrium concentration of hydrogen is...

Rhea Jain 2I

Can someone help me solve this problem? I'm not sure what I'm doing wrong. 27. A mixture of 2.5 moles H2O and 100 g of C are placed in a 50 L container and allowed to come to equilibrium subject to the following reaction: C(s) + H2O (g) ⇌ CO (g) + H2 (g) The equilibrium concentration of hydrogen is ...

Rhea Jain 2I

Can someone help me solve this problem? I'm not sure what I'm doing wrong. 19. Calculate the reaction quotient, QC, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 (g) ⇌ As (s) + H2 (g) AsH3 = 5.55 x 10-4 mol, As = 3.31 x 10-3 mol, H2 = 1.23 x ...

Rhea Jain 2I

Hi! When determining whether a ligand is polydentate, it helps to draw out the Lewis structure. If there are atoms bonded to the same central atom with lone pairs, that means they can be binding sites. For example, for a, HN(CH2CH2NH2)2, the three N atoms each have a lone pair, so this compound is t...

Rhea Jain 2I

Hello! I can walk you through the steps that I did to solve these problems. For me, I start with writing out the reactants. I'll use d (sodium hydroxide and hydrosulfuric acid) as an example. So that would look like this: NaOH(aq) + H2S(aq) Then, I would figure out which is the base and which is the...

Rhea Jain 2I

For your reactants, the acid does not dissociate because it is a strong acid and it is donating its H+ to the hydroxide group of the base. This is the case of c and d as well. For b, both the reactants dissociate because they are both weak. I don't think the salts are ever combined in the product, b...

Rhea Jain 2I

I believe that both dissociate because both the acid and base are weak in this equation. That's also why water isn't a product, as compared to the other 3 problems.

Rhea Jain 2I

Hi! This is because in the structure for b, the NH2 groups are close enough that they can coordinate simultaneously and form a ring with the same metal center. In structures a and c, the NH2 groups aren't next to each other, so they aren't close enough to form a chelating complex.

Rhea Jain 2I

The reason that water is not formed in this reaction is because water is only formed in a neutralization reaction when a strong base is present. If the base is not strong, then water will not be created.

Rhea Jain 2I

Hello! I can walk you through the steps that I did to solve these problems. For me, I start with writing out the reactants. I'll use d (sodium hydroxide and hydrosulfuric acid) as an example. So that would look like this: NaOH(aq) + H2S(aq) Then, I would figure out which is the base and which is the...

Rhea Jain 2I

For this problem, you would simply combine the given acidic oxide with water, which would produce the referenced acidic solution.

Rhea Jain 2I

The reason that water is not formed in this reaction is because water is only formed in a neutralization reaction when a strong base is present. If the base is not strong, then water will not be created.

Rhea Jain 2I

What answer did people pick for the respondus question?

Rhea Jain 2I

omggg thanks so much i was looking for these

Rhea Jain 2I

The coordination number is the number of ligands bonded to the central atom. For example, [NiCl4]2- has a coordination number of 4 because the 4 Cl atoms are bonded to the Ni.

Rhea Jain 2I

In the online textbook, when you click table of contents, there should be a 9C under chapter 9. If you scroll towards the bottom, you'll find all the 9C questions. Same goes for 6A - go to the table of contents, under chapter 6, click 6A.

Rhea Jain 2I

No, which is shown in problem 9C.7. The ligands need to be close enough to bond so they can form a ring with the same metal center for it to be a chelation complex. for 9C.7, a) and c) can't be chelation complexes, while b) can.

Rhea Jain 2I

I recommend drawing out the Lewis structures when determining whether a ligand is polydentate. If more than one binding atom has lone pairs, it should be polydentate unless there are special circumstances, like for H2O. According to this, here are the answers: a) yes, tridentate -> 3 N atoms each wi...

Rhea Jain 2I

It is by the number of lone pairs on the binding atom. If more than one binding atom has lone pairs, it is polydentate unless there are special circumstances, like for H2O.

Rhea Jain 2I

When determining whether a ligand is polydentate, I find it helpful to draw out the Lewis structure. This way, you can see if an atom has extra lone pairs that would allow it to bond again. The answers to the questions are listed below. a) yes, tridentate -> 3 N atoms each with a lone pair b) yes, m...

Rhea Jain 2I

Don't forget about resonance structures when determining the dentate of a complex! CO3 2- is a good example of this, but there are other instances as well.

Rhea Jain 2I

I read that the exam would be 60% new material and 40% material from the past two midterms. Not sure how accurate this is though.

Rhea Jain 2I

I read that the final will be out of 140 points, so i would assume around 20-25 questions, all multiple choice. There will also be a respondus question beforehand, just like the midterms. Do you know when the respondus question will be posted? I don't but it should be posted soon. If it's not poste...

Rhea Jain 2I

I think there was a typo in the textbook and the O shouldn't have been capitalized, because the answer key has the metal named as cobaltate (III). If that is the case, the whole thing should read aquapentacyanocobaltate (III) ion.

Rhea Jain 2I

Almost correct! Everything is right except for sulfate. It should read sulfato, so the whole thing reads pentaamminesulfatocobalt (III) ion.

Rhea Jain 2I

I read that the final will be out of 140 points, so i would assume around 20-25 questions, all multiple choice. There will also be a respondus question beforehand, just like the midterms.

Rhea Jain 2I

Yes, it will be the same format as the midterms. I'm not sure how many questions, but it is out of 140 points, and there will be a Respondus question beforehand.

Rhea Jain 2I

I was wondering the same thing too. It's because see-saw has a lone pair on its structure, and coordination compounds don't have lone pairs on ligands.

Rhea Jain 2I

I think we will have to, yes!

Rhea Jain 2I

We can see that the overall charge of the compound is 0. We also know that there are two chlorine atoms, each with a -1 charge, and the NH3 has a 0 charge, so the cobalt must have a +2 charge to balance out the chlorine.

Rhea Jain 2I

Consider the bonding in H2C═CHCHO (a) Draw the most important Lewis structure. Include all nonzero formal charges. (b) Identify the composition of the bonds and the hybridization of each lone pair—for example, by writing σ(H1s,C2sp^2). I was able to draw the correct Lewis structure, but I'm confused...

Rhea Jain 2I

For each pair, determine which compound has bonds with greater ionic character: (a) HCl or HI; (b) CH4 or CF4; (c) CO2 or CS2 I originally thought that the greater the difference in electronegativity between the two atoms, the more ionic character the compound has. However, the answer for b is CF4 a...

Rhea Jain 2I

Anthracene has the formula C14H10. It is similar to benzene but has three six-membered rings that share common C--C bonds, as shown below. Complete the structure by drawing in multiple bonds to satisfy the octet rule at each carbon atom. Resonance structures are possible. Draw as many as you can fin...

Rhea Jain 2I

Give the ground-state electron configuration expected for each of the following ions. I'm confused on how to do this with Cu+. The answer is [Ar]3d10. Is this because the single electron left in the 4s shell moves to complete the 3d shell? Why does this happen? And does this happen in every situatio...

Rhea Jain 2I

Hi! You were correct about the (III) indicating a 3+ charge for bismuth. For the number used in the formula, you are supposed to use the charge of the atom, not its number of valence electrons. So, with a charge of 3+, the formula would be BiF3. The number of valence electrons doesn't matter when de...

Rhea Jain 2I

Yes, you need to use Avogadro's number to convert from moles to molecules/atoms. (6.02 x 10^23)

Rhea Jain 2I

The best advice I can give is to draw out the compound's Lewis structure. Then, you can determine the direction of the dipole moments based on electron distribution, and if there is an overall direction, it is polar. If the direction is balanced, it is nonpolar.

Rhea Jain 2I

Yes, single bonds are longer than doubles, and doubles are longer than triples. To determine the bond type between two atoms, remember the octet rule and its exceptions! This will help you determine the strength and length of bonds between two atoms :)

Rhea Jain 2I

Hi!
Lone pairs are two unpaired electrons, and they can't be involved in ionic bonding. You can distinguish them in Lewis structures too! Typically, they'll be represented by either a line or two dots on the corresponding side of the atom they're involved with.

Rhea Jain 2I

Yes, threshold energy and work function are the same thing.

Rhea Jain 2I

A question will not usually say that you need to use a certain number of sig figs. When a question gives a value for something, you should use the number of sig figs in that number. If several values are given, use the least number of sig figs from all the given values.

Rhea Jain 2I

To convert m to nm, you multiply by 10^9. Try and remember that nanometers are much smaller than m, so the number becomes much larger when converting m to nm.

Rhea Jain 2I

Hi! I'd really appreciate it if someone could help me solve this problem: A 1.50-g sample of metallic tin was placed in a 26.45-g crucible and heated until all the tin had reacted with the oxygen in air to form an oxide. The crucible and product together were found to weigh 28.35 g. (a) What is the ...

Rhea Jain 2I

The difference is that in ground state, electrons in a system are in the lowest possible energy levels. The excited state is any state of the system that has a higher energy than the ground state. The ground state electron configuration of an element is the same as the regular configuration in which...

Rhea Jain 2I

Electrons don't spin up or down, it is clockwise or counterclockwise. We just use the arrows in electron configuration to distinguish the two. They need to have opposite spin because electrons are negatively charged, so they naturally repel each other, and therefore spin in opposite directions when ...

Rhea Jain 2I

Wavelength, frequency, medium, and temperature!

Rhea Jain 2I

You would have to look at the difference in electronegativity between the two atoms. If one is more electronegative than the other, it is a polar bond.

Rhea Jain 2I

Mine is the organic chemistry teacher for sure:)

Rhea Jain 2I

Yes! If you see a net charge that is going in a certain direction, it is polar. The direction is determined by which atom is more electronegative.

Rhea Jain 2I

Yes, that's correct! So if a question does not specify how many significant figures to include, we just used the same number of significant figures as the values in the question? For example, if a value in the question is 35.21 then our answer should be in 4 significant figures? Yes, but this is onl...

Rhea Jain 2I

I didn't use the density of bromopropane either, I think it's just there for consistency :)

Rhea Jain 2I

I was wondering the same thing, but I think it's because both the products had oxygen atoms, which can't be said about hydrogen and carbon.

Rhea Jain 2I

I used the molarity formula (M=mol/L). You would get 0.278M=0.0045mol/L, and you would solve to get the liters to equal 0.0162 L.

Rhea Jain 2I

I think a good way of comparing the two is to remember that the molecular formula is a multiple of the empirical formula. This is because the empirical formula gives you the most simplified ratio of the atoms in a compound while the molecular formula gives you the actual number of atoms. Hope this h...

Rhea Jain 2I

So if a question does not specify how many significant figures to include, we just used the same number of significant figures as the values in the question? For example, if a value in the question is 35.21 then our answer should be in 4 significant figures? Yes, but this is only if 35.21 is the on...

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