CHEMISTRY COMMUNITY

Edwin Liang 1I

You can go through the Board Index to find topics that correspond to each course. Clicking on a topic will lead to a subsection with many questions and answers about that topic. You can click "Post a Reply" to answer a question on a post.

Edwin Liang 1I

We are allowed to approximate 1 bar = 1 atm! There is a very small difference, though.

Edwin Liang 1I

I think it would be much later in the series, or in upper-division courses.

Edwin Liang 1I

Each value of R is different because different units are used. Use the value of R that corresponds to your problem.

Edwin Liang 1I

Kc is used for problems with molarity and Kp for calculating pressures of gas.

Edwin Liang 1I

Hi! -ate is used when there is an overall negative charge

Edwin Liang 1I

This is really confusing. I think it is because of the three oxygens attached.

Edwin Liang 1I

Yes, it would be best. Sapling provides a very concise list of these acids and bases.

Edwin Liang 1I

As mentioned in lecture, cisplatin is one of them.

Edwin Liang 1I

The coordination number is the amount of atoms bonded to the transition metal atom, so in this case, it would be 4.

Edwin Liang 1I

The work function determines the amount of energy to remove an electron from a surface. The threshold frequency is the minimum amount of radiation needed for the work function

Edwin Liang 1I

It will most likely follow a similar format to the previous midterms

Edwin Liang 1I

My TA said that there would be more of an emphasis on topics we spent more time on.

Edwin Liang 1I

Yes, memorizing them would most likely benefit greatly

Edwin Liang 1I

It is because the oxygen is much more electronegative

Edwin Liang 1I

Resonance is where a molecule's Lewis structure could be expressed in multiple ways. This is due to interchanging double bonds or triple bonds.

Edwin Liang 1I

The lone pairs want to be in the areas where there is least electron repulsion, so the two lone pairs on H2O try to be furthest away from each other

Edwin Liang 1I

Electronegativity increases from the lower left side of the table to the top right and the ionization energy increases as you go from the bottom left to top right.

Edwin Liang 1I

Drawing the molecule and seeing whether there is a difference in dipoles helps too

Edwin Liang 1I

The two are both essentially the same type of force!

Edwin Liang 1I

I don't think the order matters, as long as we can identify the bonds.

Edwin Liang 1I

For most d-block elements in period 4, you would add have [Ar] 4s2 and some number of electrons in 3d orbital. As you go along the d block, add one electron to 3d. There are exceptions, such as Cr and Cu in which the 4s orbital is missing one electron. Cr is [Ar]4s1 3d5 and Cu is [Ar]4s1 3d10

Edwin Liang 1I

The De Broglie Equation is used to find wavelengths with a mass while E=hv finds the energy of a photon at a given wavelength

Edwin Liang 1I

Dr. Lavelle will hopefully curve the grades, but it would be dependent on the final grade distribution.

Edwin Liang 1I

Dr. Lavelle will most likely discuss it in the upcoming weeks, but I believe it is cumulative. My guess is that it might have an emphasis on material after Midterm 2

Edwin Liang 1I

I think the lectures are recorded again because it saids "Online - Recorded"

Edwin Liang 1I

Hi,
In combustion reactions, the Oxygen is usually in excess unless its specific amount is given

Edwin Liang 1I

I personally quiz myself on the trends of atomic radii, ionic radii, etc by looking at different elements. I find that it helps identifying trends after short practice.

Edwin Liang 1I

Many metal cations are also able to be in Lewis reactions

Edwin Liang 1I

I think it has to do with the charge of the cation(+1, +2, +3) and the electron density of the anion. There would be a higher distortion as the anion becomes larger as the electrons in the outer shell are held weakly compared to the inner shells. The greater the charge would mean a higher attraction...

Edwin Liang 1I

Those three elements are exceptions to the octet rule. It's because of their d-orbitals.

Edwin Liang 1I

Double bonds are stronger than single bonds, so it pulls atoms closer together

Edwin Liang 1I

Hello! I started off with De Broglie's Equation, plugging in the speed of H for v and Planck's constant. To find the mass, multiply the mass of hydrogen(1.008 g/mol) by two, as it is a diatomic. Multiply this by Avogadro's Number and divide by 1000 to get Kg.(Kg is better because Planck's Constant h...

Edwin Liang 1I

I believe you mistook two separate equations for De Broglie's. Lambda = h/mv would be the equation.

Edwin Liang 1I

Avogadro's number is 6.02214 * 10^23 units. These units tell us the amount of "stuff" in a mole. For example, there are 6.02214 * 10^23 atoms of Nitrogen in a Mole of Nitrogen.

Edwin Liang 1I

For this problem, utilize the De Broglie Equation. λ = h/mv. Insert Planck's Constant and the velocity of the diatomic fluorine for h and v, respectively. Mass could be found by multiplying the atomic mass of fluorine(18.998) by 2, then multiplying that by Avogadro's number. Then you would solve for...

Edwin Liang 1I

Hello,

You would use the equations E = HV and c= λv. Convert the 2.4 μm to meters and insert that into c= λv for λ. Isolate for v, then use that to solve the E = HV equation

Edwin Liang 1I

I do not believe so as the midterm is completely MCQ.

Edwin Liang 1I

The equation Ek = HV - Φ represents the kinetic energy of the ejected electron. This is determined by finding the initial energy of the photon subtracting the threshold energy of the metal, which is the minimum energy required to eject an electron from the metal.

Edwin Liang 1I

Those equations work for photons. De Broglie's equation is for electrons.

Edwin Liang 1I

The question will most likely ask for specific units. Dr Lavelle has said either is fine unless specified.

Edwin Liang 1I

Since frequency and wavelength are directly related to one another( c = λ * v ), the slope on a wave with high frequency will be more than that with a lower frequency. This means the "extent of change" (slope) decreases as frequency decreases.

Edwin Liang 1I

Yes I believe so. Run it through with the TA first ofcourse.

Edwin Liang 1I

I don't think so. Understanding basic principles that support what we have learned is enough I think.

Edwin Liang 1I

E=hv is only usable for electromagnetic radiation.

Edwin Liang 1I

Hi! I think Professor Lavelle meant ionizing atoms, not electrons. To my understanding, ionizing atoms and electrons are different procedures.

Edwin Liang 1I

The unexpected outcome of the photoelectric experiment was that increasing the intensity of a given light would not eject electrons from a metal surface. However, increasing the wavelengths(frequency) of the light would eject electrons. This is significant because it shows the wave-particle duality ...

Edwin Liang 1I

Wave-particle duality means that electronics are both waves and particles at the same time. It has properties of both. In response to your question, there would be no particle-like behavior in long wavelengths and no wave-like behaviors in short wavelengths, so it wouldn't make sense.

Edwin Liang 1I

The threshold energy and the work function are the exact same, only with different names. In the photoelectric effect experiment, the threshold energy is the amount of energy required to displace an electron from the metal.

Edwin Liang 1I

I think a periodic table will be given during exams, but understanding certain properties and elements of the table would be beneficial.

Edwin Liang 1I

Converting from grams to moles can be done by dividing the grams of substance divided by the molar mass of the substance. For the millimoles to moles, I think multiplying by 1000 would work

Edwin Liang 1I

Yes, the empirical formula gives us the ratio of moles between each atom in the molecule, so converting the grams of products to moles would simplify it.

Edwin Liang 1I

For rough estimates, 16 is fine, but for precise calculations, 15.999 is best.

Edwin Liang 1I

Which question in the textbook are you looking at? You could take the moles of Na divided by the final volume of the solution of sodium carbonate to find the molarity.

Edwin Liang 1I

Dr. Lavelle spoke of partial credit for some problems during discussion, so there seems to be written and multiple choice questions for the exams.

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