CHEMISTRY COMMUNITY

JTieu_1L

Hi,

This post was extremely helpful thank you so much for the extra practice! :))
However, I was wondering if Matthew was able to get 1.3 for 2b. I divided 1/(.35)(.45) and got 6.3. Can someone explain how he got 1.3? Thank you!

JTieu_1L

I have attached my work below :))

JTieu_1L

4.31 Water gas is an inexpensive, low-grade fuel that can be made from coal. (a) Is the production of water gas exothermic or endothermic? The reaction is C(s) 1 H2O(g) ¡ CO(g) 1 H2(g) (b) Calculate the enthalpy change for the production of 200. L of hydrogen at 500. Torr and 65 8C by this reaction ...

JTieu_1L

Does anybody know which problems from 4D to focus on for midterm 1?

JTieu_1L

4D.3 The reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113 8C to 22.799 8C. The calorimeter assembly is known to have a total heat capacity (calorimet...

JTieu_1L

why is it that with lower pKa the stronger the acid?

JTieu_1L

Why is it that for polyprotic acids, all deprotonations are weak and insignificant?

JTieu_1L

6.19 Hemoglobin (Hb) molecules in blood carry O2 molecules from the lungs, where the concentration of oxygen is high, to the tissues where it is low (see the Interlude following Focus 5). In the tissues the equilibrium H3O1(aq) 1 HbO 2 2 (aq) ∆ HHb(aq) 1 H2O(l) 1 O2(aq) releases oxygen. When muscles...

JTieu_1L

6D.5 Calculate the pH, pOH, and percentage protonation of solute in each of the following aqueous solutions: (a) 0.057 m NH3(aq); (b) 0.162 m NH2OH(aq); (c) 0.35 m (CH3)3N(aq); (d) 0.0073 m codeine, given that the pKa of its conjugate acid is 8.21. Did anyone get 1.5% for the percentage protonation ...

JTieu_1L

For question 6D1 in the textbook, am I allowed to use table 6C1 and 6C2? 6D.1 Calculate the pH, pOH, and percentage deprotonation of each of the following aqueous solutions: (a) 0.20 m CH3COOH(aq); (b) 0.20 m CCl3COOH(aq); (c) 0.20 m HCOOH(aq). (d) Explain any differences in pH on the basis of molec...

JTieu_1L

6C.7 Use data from Tables 6C.1 and 6C.2 to place the following
acids in order of increasing strength: HNO2, HClO2, +
NH3OH,
(CH3)2NH2+

I cant seem to find the pka or pkb for the last two, does anyone have the same problem?

JTieu_1L

Why did Lavelle add 10^-10 to 10^-7 in today's lecture? (10/15)

JTieu_1L

Are Outline 1 and Outline 2 going to be the only sections tested in Midterm 1?

JTieu_1L

6A.23 Calculate the molar concentration of Ba(OH)2(aq)
and the molar concentrations of Ba21, OH2, and H3O1 in an
aqueous solution that contains 0.43 g of Ba(OH)2 in 0.100 L of
solution

Why is the concentration of Ba2+ the same as barium hydroxide?

JTieu_1L

Oops, sorry y'all I read the question wrong. I was wondering why X2 --> 2X was endothermic and the textbook states that X is a halogen so I thought endothermic reactions were directly linked with halogens. But in reality, because that molecule is being broken, it requires an input of energy, making ...

JTieu_1L

5.35 The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases. Use this plot to do the following: (a) Write a balanced chemical equation for the reaction. (b) Calculate the equ...

JTieu_1L

Why does increasing temperature increase the products, when not given if the reaction is exo or endothermic? Is it because all the other options do not make sense? Question: Which of the following changes will produce the composition shown? (a) Increasing the temperature. (b) Adding X atoms. (c) Dec...

JTieu_1L

How is it that with a presence of a HALOGEN, the reaction is exothermic?

JTieu_1L

If I get two positive numbers from my using the quadratic formula to find X, how do I know which one to use? Do I have to plug those numbers into the quadratic equation again to see which one is true?

JTieu_1L

If given concentrations of reactants and products and the question asks to calculate Kp why don't you convert those molarity concentrations into bars or atm? I thought that if given concentrations and asked for Kp, you would have to use the Ideal Gas Law. Why don't you?

JTieu_1L

induced dipole induced dipole
- since there are uneven movement of electrons in molecules they create temporary dipole moments

JTieu_1L

latin names only for anions

JTieu_1L

l = 1,2,3,4,5,6

l = 1,2,3,... (n-1)

JTieu_1L

cis on the same side and trans on opposite (molecules with lone pairs) - refer to cisplatin as an example

JTieu_1L

We do not need to know if it's tetrahedral or square planar yet but we do know that myoglobin is made out of a square planar with poryphorin.

JTieu_1L

Hemoglobin is able to transport 4 molecules of oxygen whereas myoglobin transfers one. This is because hemogloblin is made out of four myoglobins.

JTieu_1L

Why is sulphurous acid stronger than carbonic acid?

JTieu_1L

Why does the titration reaction written by lavelle in lecture have the equilibrium arrows? Aren't the really strong acids and bases? Does the one arrow only apply to singular acids and bases?

JTieu_1L

For linkage isomerism, how do you know which preference of interaction is stronger?

JTieu_1L

how would you find the unhybridized orbitals using electron configuration? what would be the pi bonds for CH3CN?

JTieu_1L

Why are there coefficients in front of NH3, H+, NH4+ in the neutralization reaction for the formation of ammonium phosphate?

JTieu_1L

Why is CH3COOH considered to be a weaker acid than HCl? Since it lost its acidic Hydrogen atom, shouldn't that still be considered a strong acid? Does that mean you disregard the fact that there is only one acidic Hydrogen atom in acetic acid and consider all 4 Hydrogen atoms, when looking for depro...

JTieu_1L

How would you identify acids and bases? For example, what would be the explanation for why HNO3 would be an acid?

JTieu_1L

Why are molecules such as CH3COOH willing to donate a H proton compared to molecules such as NH3? Is the CH3COOH not stable in that form?

JTieu_1L

Why is it that with longer bond from Br in Hydrobromic acid makes it stronger compared to HCl? I thought that with longer bond length, the atoms would not be closer to each other and therefore not as strong.

JTieu_1L

How do you know if atoms lie in the same plane? Is it by bond angles? So if they share similar bond angles, they lie in the same plane?

JTieu_1L

In the textbook, it says that terminal atoms such as Cl have not been regarded as hybridized, why is that?

JTieu_1L

How many questions are usually on the final?

JTieu_1L

2F.15 Noting that the bond angle of an sp3 hybridized atom is 109.5 and that of an sp 2 hybridized atom is 120 8, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? Can someone explain why the bond angle would increase wit...

JTieu_1L

Does anybody know if CHEM14B with Lavelle is asynchronous?

JTieu_1L

What is interaction potential energy and why is it negative?

JTieu_1L

Can period 5 elements have the subshell f? Since it can equal to 0,1,2,3,4

JTieu_1L

Why aren't all resonance structures equal?

JTieu_1L

Would we know how to draw lewis structures like (CH3)2SO?

JTieu_1L

do we need to know about hybridization?

JTieu_1L

Why would you draw AlCl3 as a covalent molecule?

JTieu_1L

Do we need to know about diagonal relationships in the periodic table?

JTieu_1L

What does this mean "The reason for the very rapid falling off of the dipole–dipole interaction is that as the distance between molecules increases, the opposite partial charges on each molecule appear to merge and cancel, whereas in the interaction between a point charge and a dipole, only the...

JTieu_1L

Does Midterm 2 cover material up to the lecture on Wednesday of week 6?

JTieu_1L

Why is it that some time later the fluctuating electron density is different?

JTieu_1L

https://pin.it/7L5UBKN

In this problem what does it mean by dominant contribution resonance hybrid mean? How would you go about this problem?

JTieu_1L

Are we required to remember the molecular formula for nitrite, nitrate, phosphate ions?

JTieu_1L

Why are ion and ion interactions stronger?

JTieu_1L

What does Lavelle mean when he says energy is released? Does that mean energy is released when a molecule and another molecule interact with each other? Or does he mean that the energy is positive when trying to break a bond and negative when create a bond?

JTieu_1L

What does the unit debye mean? Is it the charge or strength of the pulling of electrons between the covalent bond? Or the overall charge?

JTieu_1L

Do ions lose their electrons from the s state first or p state or d state?

JTieu_1L

Why does Fe form Fe 2+ and Fe 3+ and why does Cu for Cu+ and Cu2+? I get how iron and copper can form Fe 2+ and Cu 2+ since they have 2 electrons in the s state but why would Fe lose 3 electrons and why would copper lose 1? The book mentioned something about different oxidation states, but I don't c...

JTieu_1L

Does anybody understand the inert-pair effect and why it occurs?

JTieu_1L

Why is the second ionization energy of an atom always higher than its first ionization energy?

JTieu_1L

If the spin state switches from +1/2 to -1/2 in a given orbital, does that mean the atom is in an excited state? For question 1E7, the Nitrogen is shown to have different direction of spins, up, down, up. The question asks if this atom is in excited or ground state.

JTieu_1L

Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron. (b) Value of n. (c) Value of l. (d) Radius of the atom. Which answers would be different for a hydrogen atom and in what way would they be differ...

JTieu_1L

"The experimental electron configuration of chromium is [Ar]3d^54s^1 instead of [Ar]3d^1 4s^2 , and that of copper is [Ar]3d^10 4s^1 instead of [Ar]3d^9 4s^2 . This apparent discrepancy occurs because the half-complete subshell configuration d5 and the complete subshell configuration d10 turn o...

JTieu_1L

Since it is excited to n=6 that means it start either from n =1, 2, 3, 4, or 5. This then means that there will be 5 spectral lines since there are only 5 energy levels to start from. To find the max you would have to start from the highest starting energy level (n=5) to n=6. Use the formula E = -hR...

JTieu_1L

Nitrogen and Fluorine have higher nuclear charge since that have more electrons. This stronger charge makes it harder for them to lose an electron; electrons are more tightly held. This then means that they have lower ionization energy. Additionally they would have higher electron affinity, wanting ...

JTieu_1L

The px, py, and pz is specifying which orbital the electron is at in the p orbital. We know that the s orbital has only one orbital, the p orbital has 3 orbitals which can hold 6 electrons. Those three orbitals in the p subshell is px, py, and pz. If asked to draw the electrons in these subshells th...

JTieu_1L

When the book refers to higher energy or lower energy, does it mean the energy of the electron or the energy of the atom? Or does it refer to energy level? For example, the book mentions energies in orbitals are degenerate in H-atoms, what does the word "energy" mean in this context? Anoth...

JTieu_1L

"r is the distance of electron 1 from the nucleus, r is the distance of electron 2 from 12 the nucleus, and r12 is the distance between the two electrons. The two terms with nega- tive signs (indicating that the potential energy decreases as r1 or r2 decreases when the electron approaches the n...

JTieu_1L

What does it mean by "given off as a photon" in the statement "High energy electrons drop to lower energy level, difference in energy is given off as a photon". I thought the energy of photon is what causes the excitement or transition of energy levels.

JTieu_1L

Where did E=pv and E=pc come from? What are they supposed to be? A part of einstein's equation? What is it trying to prove or associate?

JTieu_1L

Is Rydberg's equation only used for H atoms?

JTieu_1L

Even if the energy of the photon is less than the work function does the energy still get absorbed, regardless if it does not eject an electron? (in photoelectric effect)

JTieu_1L

What is the reason for why 3d goes before 4s other than the fact from how it is arranged in the periodic table?

JTieu_1L

Hi!
I was wondering the difference between Workshops and Step-Up Sessions, do I have to sign up to join a Workshop meeting? And if I do, where?

JTieu_1L

Sapling HW "A red line is observed at 656.3 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line". I understand that since the wavelength is in the visible ...

JTieu_1L

I am not too sure about what Schrodinger Equation means, but to my understanding, is the following statement correct? So, each wave function gives rise to different electron densities. And when you square the wave function (Hamiltonian in the formula) it gives you that specific electron density (whe...

JTieu_1L

Hi,

I was just wondering what numbers in 1D exercises only covers material up to 1D2? (since Professor Lavelle sent an email saying its topics to 1D.2)

JTieu_1L

In Professor Lavelle's lecture, he stated that the intensity is proportional to the number of photons, but I thought it would be the energy in each photon and not the number; since it is a one photon to one electron interaction. Can someone please clarify this for me please?

JTieu_1L

Hi, I don't if I am understanding this correctly, can someone verify if the following statement is true? To my understanding E = h(nu) can only be applied to find the energy in joules of a photon, however, this formula can be applied to find the energy required to remove an electron only if the kine...

JTieu_1L

What does Professor Lavelle mean when he says "waves cancel each other out"?

JTieu_1L

Oh wait, never mind. In Professor's Lavelle website, the "Solutions Manual Error" pdf states that n2 should be n=1.

JTieu_1L

Question 1.A.15: "In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6 nm. Determine the values of n for the initial and final energy levels of the electron during the emission of energy that leads to this spectral line." Should the answer be n2 = 3 and n1 = 1, since...

JTieu_1L

"For the Lyman series, the lower energy level is n=1; for the Balmer series, n=2; for the Paschen series, n=3; and for the Brackett series, n=4." Can someone explain the concept of these series? Does it mean that for the Paschen series, the electron starts at the energy level n=3, then get...

JTieu_1L

What is the difference between a quantitative and qualitative statement?

JTieu_1L

Does anyone know if we have to remember the frequencies/wavelengths of the electromagnetic spectrum? Or will it always be given for midterms?

JTieu_1L

In the post assessment in Photoelectric Effect #28, the work function units given is kJ.mol^-1, does this mean that to find the threshold energy or energy required to remove an electron from the work function, you divide by Avogadro's number?

JTieu_1L

Question: 23. In some experiments electrons display particle-like properties and in other experiments electrons display wave-like properties. True or false?

Why is this "True"?

JTieu_1L

Question 34. "If an electron (mass 9.11 x 10-31 kg) has an associated wavelength of 7.28 x 10-9 m, what is its speed? Is your answer reasonable, why?" A. 1.00 x 10-5 m.s-1. Yes. 1.00 x 10-5 m.s-1 is reasonable for e- as it is less than the speed of light, c = 3.0 x 108m.s-1. B.1.00 x 10-5 ...

JTieu_1L

19. Which one of following is not describing the photoelectric effect?
A. E (photon) – E (remove e-) = E (excess)
B. E (photon) – E (remove e-) = EK (e-) C. hv - work function = 1/2mv2
D. λv = c
E. None of the above

JTieu_1L

CuSO4 is stated to be an aq solution which means that by taking the amount of mol of CuSO4 x H20 you can figure out the mass of CuSO4 x 5H2O. CuSO4 (aq) is the same as CuSO4 x 5H2O, however, CuSO4 is not the same as CuSO4 (aq)

Here is how I figure it out: https://pin.it/2sLkaxX

Hope this helps!

JTieu_1L

Hi! You can always find the mass percentage composition by the mass of each element then dividing the mass of the entire molecule and multiplying it by 100. E.g. Find the mass percentage composition of C,H, O, from C6H12O6. Let's find the mass of the the entire glucose molecule (C6H12O6) 1. You calc...

JTieu_1L

Yes, there is!

Here is the link: https://groupme.com/join_group/62288203/dSSkobMS

JTieu_1L

Use the formula for converting formula units (atoms, molecules, ions, etc.) and moles. N = nNA N: the number of atoms, ions, molecules, objects n: amount of moles in the substance NA: Avogadro's number (6.02 x 10^23) Remember that the length of one atom is equal to its diameter (d = 2r) Here is how ...

JTieu_1L

Here is how I did it: https://pin.it/7A48fBS

Remember the law of conservation of mass. Mass of REACTANTS must equal to mass of PRODUCTS in a chemical equation.

JTieu_1L

Hi!

Make sure you are using the numbers from your calculator and not round as you go.

Here is what I did:

https://pin.it/3XHNgTi

JTieu_1L

He associates this type of chemical reaction that involves, O2 as one of the reactants and CO2 and H2O as the products, to the words "combustion, burning, and oxidation". So if in a question you see any of those three words, you would know how to write the chemical reaction.

JTieu_1L

Hi,
to start off you need to find the molecular formulas of each!
https://pin.it/4BEtNTy

JTieu_1L

Hi Cecilia, the three sig figs from the answer (93.1%) may be based from the amount of sig figs form CO2 (17.5g). Here is the question: When limestone, which is principally CaCO3, is heated, carbon dioxide and quicklime, CaO, are produced by the reaction CaCO3(s) --> CaO(s) + CO2(g). If 17.5 g of CO...

JTieu_1L

I came across this question while doing the Fundamental problems of H and I do not understand how to balance the second stage chemical reaction: "In one stage in the commercial production of iron metal in a blast furnace, the iron(III) oxide, Fe2O3, reacts with carbon monoxide to form solid Fe3...

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