CHEMISTRY COMMUNITY

Amir Bayat

https://chem.libretexts.org/@api/deki/files/128300/clipboard_e26a57bebc918920030b137efb13b763a.png?revision=1

That link leads to an image which explains the differences of both cells on a diagram. Hope it helps :)

Amir Bayat

I believe that we will be predominantly using the pre-equilibrium method judging by the homework problems.

Amir Bayat

When they touch together, they technically are binding together with weak, longer bonds, but these can sometimes be broken up. When colliding with a higher activation energy, the bonds become stronger, and fusion can occur.

Amir Bayat

Why is it that kinetic control predominates at low temperatures and that the reaction pathway with the lower activation energy will predominate at low temperature?

Amir Bayat

How is the reaction in part B second order? The answer key says it is. 7B.17 Calculate the time required for each of the following second-order reactions to take place: (a) 2 A -> B + C, for the concentration of A to decrease from 0.10 mol*L21 to 0.080 mol*L21, given that kr 5 0.015 L*mol^-1* min^2 ...

Amir Bayat

The rate of formation requires one molecule of the atom versus the rate of formation requiring two molecules of the atom colliding at the same instant for a second order. The exponents of the rate laws will tell you if it is first, second, or zero order.

Amir Bayat

When there is not a solid substance in the cell diagram.

Amir Bayat

When do you place the products in the rate of reaction as the denominator versus when you only place the reactants for the rate of reaction. In the homework problems for 7A, you see the reactants only written in the rate laws, but in the textbook, the rate laws also include products as denominators....

Amir Bayat

How would the pH affect the oxidizing strength of a compound? Like in the problem below: 6.44 State how the oxidizing strength of each of the following oxidizing agents would be affected by raising the pH (stronger, weaker, or no change): (a) Br2; (b) MnO42; (c) NO32; (d) ClO42; (e) Cu21. Justify yo...

Amir Bayat

What is emf and why does it represent the maximum potential difference?

Amir Bayat

What is the formula for calculating Q for these problems?

Amir Bayat

Is corrosion going to be on the test? I do not recall going over it in class.

Also, if it is, can someone explain what occurs in this process?

Amir Bayat

Can someone explain what occurs in galvanic and voltaic cells?

Amir Bayat

Do we have to be able to draw out cell diagrams on the test?

Amir Bayat

If not given which is which, we can tell through whether half-reaction is reduced or oxidized. This can be told through the greater electric standard potential of the reaction, the greater or more positive standard electric potential is the reduction reaction and the other is the oxidation reaction....

Amir Bayat

The net charge is the oxidation number of the element multiplied by the amount of that element available. Therefore the oxidation number is not necessarily the charge, but it can be utilized to find the charge.

Amir Bayat

Maya Beal Dis 1D wrote:Does this mean that material covered before the midterm will not be on test 2 at all?

Test 2 mainly focuses on the material after the midterm, so I doubt that there will be any prior material added to it.

Amir Bayat

Yes, an increase in the oxidation number of an element can be more commonly defined as reduction.

Amir Bayat

5J.15 Calculate the equilibrium constant at 25 8C and at 150 8C for each of the following reactions, using data available in Appendix 2A: (a) NH4Cl(s) ∆ NH3(g) 1 HCl(g) (b) H2(g) 1 D2O(l) ∆ D2(g) 1 H2O(l) In the question above, how would you use the method described in the textbook of with the equat...

Amir Bayat

It usually depends on the units of Rydberg's constant as well. If you want to use an equation where Rydberg's constant is in K, which in most equations it is, make sure to convert, if not, then there is no need to convert. Therefore, always look at the units of Rydberg's constant, this is why is is ...

Amir Bayat

Also,

When is the change in internal energy zero for an irreversible expansion?

Amir Bayat

What are intensive and extensive properties? I know we touched on them during class and in Lyndon's review session, but can someone please state examples of them?

Amir Bayat

Is fusion the same as melting? I am confused, are they synonyms of one another or antonyms?

Amir Bayat

What is the difference between the change in entropy for a reversible isothermal expansion vs an irreversible expansion? Are they exactly the same?

Amir Bayat

How does q(rev) become enthalpy in Lavelle's lecture? I recall the notes and have them written down, but does it not state that heat must be at constant pressure to be the same as the change in enthalpy of the system? A reversible isothermal expansion has a changing pressure.

Amir Bayat

What are the effects of fossil fuels on the environment in terms of the laws of thermodynamics?

Amir Bayat

The temperature, state of matter, and volume all can shift the chemical anatomy of a molecule. This shift in positionally allows for the molecule to have a higher or lower chance of disorganization and thus increasing or decreasing the entropy of the system.

Amir Bayat

Are the final exams still there in Young Hall? And if they are not there, where would they be now?

Amir Bayat

Since there is no change in the temperature of the system, there is essentially no change in the internal energy of the system as well.

Amir Bayat

Isothermal processes are at constant temperature so there is no heat being added or removed from the system. Therefore, the internal energy of the system does not change and then q = -w

Amir Bayat

805097738 wrote:so the surrounding is the universe?

Essentially yes, the surrounding can be the universe. However the system is what we are specifically observing in the universe.

Amir Bayat

State property as there can be a change in U with Ufinal-Uinitial

Amir Bayat

Expansion work is when pressure is applied to the object

Amir Bayat

A closed system can exchange energy with its surroundings, however, an isolated is unable to exchange energy (nor matter) with its surroundings.

Amir Bayat

A Lewis acid is a proton donor while a Lewis base is a proton acceptor.

Amir Bayat

irreversible work has a constant pressure so you can simply take it out of the integral However, reversible work can have a changing pressure, thus the equation changes as both work and the volume change. We must then define pressure in the changing factors it has of nRT, where temperature or the mo...

Amir Bayat

If the stoichiometric coefficients differ from one or there is a pure substance (you would do nothing)

Amir Bayat

You look at the number of moles in addition to the concentrations. If there are 2 moles of a substance, then you need to multiply the "X" value by that number of moles - which is 2 in this case.

Amir Bayat

Use whichever is more convenient to you, if the question does not ask for an explicit type of equilibrium constant.

Amir Bayat

Anything less than 10^-3 is a valid use of approximation if the percent ionization/protonization/deprotonization is less than 5%.

Amir Bayat

Yes, pure substances are the only forms of a substance which are not included in the equilibrium constant. Gases and aqueous solutions are not pure substances.

Amir Bayat

The gas constants are different because they are in different units. When given gas constants, typically utilize the one in which you have the units for.

Amir Bayat

Kw is essentially the Hydronium Ion Concentration times the Hydroxide Ion Concentration. The Ka and Kb values determine involve these concentrations in their products for weak acids and weak bases. Therefore, when the conjugate base or acid pair's K values are multiplied, they cancel out everything ...

Amir Bayat

A smaller K value generally means that the reactants are in favor with the products. If a K value is too large, that means the products are too favored and the reaction needs to keep on going forward to reach an equilibrium state and this makes it harder for it to shift back and forth.

Amir Bayat

They are all equilibrium constants. The only reason that they have different names is to specify what they are determining. Kp is the partial pressure, Kw is the neutral water, Kc is the concentration, Ka is the weak acid, etc.

Amir Bayat

If the percent deprotonization or percent protonization is less than 5%, then the x value is valid. If it is not, then the quadratic formula is required and an estimate is not a safe approximation for the reaction.

Amir Bayat

Test 1 begins January 21st.

The topics that are going to be covered are Acids and Bases and Chemical Equilibrium.

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Solids and liquids are pure substances and therefore do not have concentrations or pressures.

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The stoichiometric coefficients are the powers that the concentration or pressure of the product or reactant are raised to.

Amir Bayat

If K is small (K < 10^-3), then there are more reactants at equilibrium and it sits to the left.
If K is large (K>10^3), then there are more products at equilibrium and it sits to the right.
If K is 1 (which is rare), then neither side is favored.

Amir Bayat

Solids and liquids are not included in the reaction quotient since they are pure substances and do not have pressures/concentrations.

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Angela Patel 2J wrote:What is chemical activity?

Chemical activity is a unit of measurement. It measures the effective concentration of an element in a mixture. It determines the real chemical potential for a real solution rather than an ideal solution.

Amir Bayat

What is the difference between donating a proton vs accepting an electron?

I know this defines the difference between Lewis acids and bases and Bronsted acids and bases, but what is the difference conceptually?

Amir Bayat

Lewis acids also typically have a hydrogen ion in front of the name of the molecule. For instance, HCl or HBr.

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Strong acid: almost all the molecules are deprotonated in the solution
Weak acid: only a small fraction of the molecules or ions are deprotonated in the solution.

Amir Bayat

The ground state generally refers to the ion that is named. Therefore, when calcium ion is given, we write the electron configuration of Ca 2+. For future problems, typically refer to the ion or atom stated in the question.

Amir Bayat

To balance the equations we look at the charges of each ion and use multiples of those ions to make their charges cancel each other out.

For example, since calcium has a (+2) charge and the anion has a (-3) charge, we have 3 Ca and 2 of the anion.

Amir Bayat

Jade Hinds 3G wrote:Amphiprotic= a substance that can both accept and donate a proton (has characteristics of both an acid and a base)

amphiprotic vs. amphoteric:
-a substance is amphoteric when its reaction acts as an acid and as a base
-amphiprotic only applies to protic compounds

What are protic compounds?

Amir Bayat

The many oxidation states allow them to transfer electrons more easily as the difference in energy between the oxidation states is not too high.

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To name a coordination compound you follow the following format: Cation first so ... Greek Prefix - Ligands (the names in alphabetical order) - TM Cation Name - Roman Numeral The prefixes to indicate the ligand names are mono-, di-, tri-, penta-, hexa-, etc Anion second ... The anion has an -o at th...

Amir Bayat

If one atom of a molecule that has the same number of atoms all around has a double bond or more, does it have a larger dipole moment, making the molecule polar? For instance, NO3-? I understand NO3 is an atom, but generally speaking, does the double bond on one of the oxygen atoms make the whole mo...

Amir Bayat

For question 2(b) we are asked to determine the hybridization for the carbon atom in HCOOH. How would one solve this?

Amir Bayat

Could someone please explain how to solve the first problem in Worksheet 6? The problem asks... For the following nitrogen oxide compounds: a. Draw the most stable lewis structure. b. Determine the shape. c. Determine whether the compound is polar or nonpolar. Nitric Oxide (NO) Nitrogen Dioxide ( NO...

Amir Bayat

Yep, electron arrangement is only determined using the # of regions of electron density, while the molecule's shape is determined using the actual number of lone pairs and bond pairs. This means that molecules with different shapes (and different formulas, ex: AX4E for SF4) can have the same electr...

Amir Bayat

Being the central atom, A, does not have subscripts. We look at the shapes of molecules using the central atom and the atoms that it is bonded to. No shape will have an A with a subscript.

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Why is a sigma bond more stable than a pi bond?

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Or more specifically, the regions of electron density can help determine the number of hybrid orbitals.

Amir Bayat

Correct, the atoms in the molecule determine the shape of it. The regions of electron density help us identify its hybridization.

Amir Bayat

In the lecture today, Doctor Lavelle mentioned energy increasing in hybridization. Does the energy of the molecule increase when we hybridize it or is there a required energy input into the molecule required for hybridization to occur?

Amir Bayat

When do we hybridize a molecule? Are all molecules from now on going to contain hybridized bonds?

Amir Bayat

Additionally, molecules with greater surface area allow for stronger intermolecular forces.

Amir Bayat

The arrangement influences how close one atom can get to another atom. The amount of bonds the central atom has also affects how likely it is to interact with other atoms or molecules.

Amir Bayat

How can you calculate the bond angle values for part (c) of the question? The question is stated below. (a) What is the shape of a thionyl chloride molecule, SOCl2? Sulfur is the central atom. (b) How many different OSCl bond angles are there in this molecule? (c) What values are expected for the OS...

Amir Bayat

Doctor Lavelle said that it would take at least a week to grade the midterms due to the vast amount of students in the class and partial credit grading system.

Amir Bayat

A trick for finding nonpolar bonds are diatomic molecules. Since the electronegativity difference is zero between two of the same atom, the bonds are nonpolar and the electrons are equally shared between the two atoms.

Amir Bayat

Always draw lone pair electrons. Question 2a) did not draw them because all the electrons were properly bonded.

Amir Bayat

At what threshold or maximum value can wavelike properties not be detected anymore?

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At what de Broglie wavelength can the wavelike properties be detected?

Amir Bayat

If a certain frequency of radiation is not ejecting electrons from the surface of a metal, is it possible to eject electrons by increasing the intensity of the incident radiation? How would we solve a question such as the question stated above? Does the intensity refer to the wavelength of the radia...

Amir Bayat

Correct, the electronegativity increases to the right and up on the Periodic Table - so do ionization energy and electron affinity.

Amir Bayat

Ionic compounds are drawn through their Lewis Structures with a bracket around the entire structure and the charge on the top right corner.

Amir Bayat

Karyn How 1J wrote:For this week’s homework, I would just do it on chemical bonds outline just to be safe since that’s what we are currently learning.

I agree, it would be safer to do some problems from the Chemical Bonds section to turn in.

Amir Bayat

The Sigma and Pi bonds will not be on the exam. They are chemistry topics that we will learn later on.

Amir Bayat

Do we need to know ions like those in question 2C for the midterm on Wednesday? The question 2C states: Draw the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion, including double bonds in different positions...

Amir Bayat

Thank you

Amir Bayat

The question 2C states: Draw the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion, including double bonds in different positions), for (a) periodate ion; (b) hydrogen phosphate ion; (c) chloric acid; (d) arse...

Amir Bayat

The question 2C states: Draw the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion, including double bonds in different positions), for (a) periodate ion; (b) hydrogen phosphate ion; (c) chloric acid; (d) arse...

Amir Bayat

For part (b), how do you arrange the potassium atoms around the phosphorous atom for the Lewis Structure Diagram? Do they revolve around the phosphorous atom, or can we arrange them separate from the potassium atom?

Amir Bayat

Doctor Lavelle claimed in class that they were electrons that move around, while the atoms do not change position in the Lewis Dot Structure. He also mentioned that we will be going over them later on and they do not pertain right now They are also defined as covalent bonds where two lobes of an orb...

Amir Bayat

In class today, Doctor Lavelle talked about how there are different methods in drawing the Lewis Dot Structures for different molecules like sulfate. How do we know, again, which structure is more stable? Is it when the central atom has a formal charge of 0?

Amir Bayat

For this question and all questions alike, is the notation for the valence-shell configuration the notation that Doctor Lavelle showed in class with the up arrows and down arrows as well, or is it just the orbitals, group numbers, and more like for example 3p^6?

Amir Bayat

Could someone please explain part (a) of this question? Does n increasing pertain to the energy of the atom or the energy of the electron as well?

Amir Bayat

(c) cannot exist in an atom as the g-orbital is not possible with n = 4 as l can only reach up to a maximum of 3. 3 does not pertain to the g-orbital.

(d) is possible as n=6, and thus l = 5. At l = 5, there exists the f - orbital.

Amir Bayat

Since there are two electrons in an orbital, we multiply the orbital by 2 get the total number of electrons in a subshell. a) A p-orbital claims that there are three orbitals, so 2 * 3 = 6 electrons. b) d has 5 orbitals, so 2 *5 = 10 electrons. c) s has 1 orbital, so 2 * 1 = 2 electrons. d) f has 7 ...

Amir Bayat

Black body radiation claims that as the temperature increases, the wavelength of light decreases.

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The Cr and Cu are exceptions as they are not stable with the Cr: [Ar] 3d^4 4s^2 and Cu: [Ar] 3d^9 4s^2 orbital equations.

They only need part of the d-suborbital filled to remain stable.

Amir Bayat

The Rydberg equation can also be seen in the change in energy formula, where energy initial is subtracted from the energy initial.

The Rydberg equation's purpose is to find the change in energy (noted by Doctor Lavelle to be for an H-atom).

Amir Bayat

This statement is accurate, the images online can help clarify this confusion. The symmetry of the orbitals can be seen on the graphs, and it is observed that the s orbital is purely symmetrical while the other orbitals are not. To explain the symmetry aspect (I am confused about the density part as...

Amir Bayat

For part (b) we convert the mg of Na to moles of Na and then multiply by Avogadro's number to get the number of atoms of Na. We then multiply by the energy in part (a) to get how much energy is emitted by 5 mg of Na. For part (c) we multiply the energy from part (a) by Avogadro's number to get the l...

Amir Bayat

The question says: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series or Lyman series, as shown in Fig. 1A.10). What is common to the lines within a series that makes grouping them together logical? How do you go a...

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