CHEMISTRY COMMUNITY

Ziyan Wang 3J

When SO3 dissolves in water, it becomes H2SO4, the sulfate acid. For c and d, if they react with acidic matter, they can act as a base. If they react with basic matter, they can act as an acid.

Ziyan Wang 3J

Yes, Ag+ + e- -> Ag, it can accept electron to be back to original state,. By definition, it is a Lewis acid.

Ziyan Wang 3J

Why is not NH3 both a Bronsted acid and base? I think that it can both gain an H to form NH4+ and lose an H to be NH2-, so it should be amphoteric.

Ziyan Wang 3J

Why is [Co(CN)5(OH2)]2- aquapentacyano cobaltate(Ⅲ) instead of aquapentacyano cobalt(Ⅲ)

Ziyan Wang 3J

Why is [Fe(CN)6] 4- hexacyanoferrate(Ⅱ) instead of hexacyanoiron(Ⅱ)?

Ziyan Wang 3J

Organic acids and bases are usually weak.

Ziyan Wang 3J

Bronsted acid: hydrogen donor,
Bronsted base: hydrogen acceptor

Ziyan Wang 3J

Since Cl has larger radius, which means that the attraction between H and Cl is weaker, so HCl is more easily to lose the proton.

Ziyan Wang 3J

pKa = -log[Ka], pKa usually have a range of 0 to 14

Ziyan Wang 3J

Yes, you can regard strong acids to dissociate completely.

Ziyan Wang 3J

My answer is that for first C: sp3,109.5,4 sigma, 0 pi, for second C: sp, 180, 2 sigma, 2 pi

Ziyan Wang 3J

I did it. My answer is that for first C: sp3,109.5,4 sigma, 0 pi, for second C: sp, 180, 2 sigma, 2 pi

Ziyan Wang 3J

In hybridization theory, lone pairs and bonding pairs are the same.

Ziyan Wang 3J

It always occur if the atom has more than one electron domain.

Ziyan Wang 3J

Yes, it's basically the same rule as the one without lone pairs. 2 electron domains -> sp, 3 -> sp2, 4 -> sp3, 5 -> sp3d, 6 -> sp3d2

Ziyan Wang 3J

In order to fulfill octet rule, there must be two lone pairs of electron around O (since bonding pairs only account for four electrons), thus O have 4 electron domains and its bonding angle is 109.5 (similar to tetrahedral).

Ziyan Wang 3J

I think it will be similar to test1.

Ziyan Wang 3J

Linear: 180
Trigonal planar: 120
Tetrahedral: 109.5
Trigonal bipyramidal: trigonal bond angle: 120, axial bond angle: 90 and 180
Octahedral: 90 and 180

Ziyan Wang 3J

Arrange the anions Cl-, Br-, N 3-, and O 2- in order of increasing polarizability. What's the general rule of polarizability?

Ziyan Wang 3J

Why is the shape of IF4 - is square planar, instead of octahedral?

Ziyan Wang 3J

Electronegativity is larger when you move close to upper right corner of the periodic table (F is the largest).

Ziyan Wang 3J

Speed is constant (3.00*10^8 m/s), and it equals to wavelength*frequency.

Ziyan Wang 3J

How to draw the Lewis structure for N5+? (N is connected in a chain)?

Ziyan Wang 3J

What is the general principles of when we should conform octet rule and when not?

Ziyan Wang 3J

I don't quite understand how to draw the Lewis structure of ICl2 +, ICl4 -, ICl3, ICl5

Ziyan Wang 3J

Valence electrons just refer to the electrons at the outermost shell. It increases down the group.

Ziyan Wang 3J

Kristina Rizo 3K wrote:Do you have a question regarding how to figure out the ground-state electron configurations?

Yes, I don't quite understand which electrons to remove.

Ziyan Wang 3J

Why can we say some species with odd number valence electrons are radicals? Is the converse-negative statement also true? (Does species with even pair of electrons necessarily mean that they are not radicals?)

Ziyan Wang 3J

I don't quite get when we draw the Lewis structure, how do we know which atom is in the middle.

Ziyan Wang 3J

Give the ground-state electron configuration expected for each of the following ions: (a) Cu+ (b) Bi 3+ (c) Ga 3+ (d) Tl 3+

Ziyan Wang 3J

Give the number of valence electrons (including d electrons) for each of the following elements. (a) Sb (b) Si (c) Mn (d) B.

I wonder why the answer for (a) is 5 but that for (c) is 7.

Ziyan Wang 3J

Cations are smaller because it reduces the energy level of valence electron by 1.

Anions are bigger because the repulsion force between electrons pushes electron outward.

Ziyan Wang 3J

I think we are not required to calculate Schrodinger's function, but only need to know s-, p-, d-, f- orbitals (it's one of the conclusions of Schrodinger's function).

Ziyan Wang 3J

It doesn't matter which orbit of x,y,z the electron actually is in because it's symmetric. You can define your x axis according to your own wish. It's just a convention to write x before y and z.

Ziyan Wang 3J

The 4 quantum numbers describe a specific electron in a specific atom/ion. For each electron in atom/ion, it has a different quantum number.

Ziyan Wang 3J

Yes, electrons with higher energy level are always removed first, and always in -f -p -d -s order

Ziyan Wang 3J

Because for some objects (such as photon), they have no mass, but they have momentum. It will be non-sense to write it into delta x * m * delta v>= h/4pi for those objects.

Ziyan Wang 3J

Energy per photon=h*c/lambda=6.63*10^-34*3.00*10^8/(420*10^-9)=4.74*10^-19
Total energy= 32*2=64
# of photons= Total energy/energy per photon=64/(4.74*10^-19)=1.35*10^20

Ziyan Wang 3J

Energy per photon=h*c/lambda=6.63*10^-34*3.00*10^8/(420*10^-9)=4.74*10^-19
Total energy= 32*2=64
# of photons= Total energy/energy per photon=64/(4.74*10^-19)=1.35*10^20

Ziyan Wang 3J

It just depends on what is given in the problem and what does the problem ask you to do. For example, given frequency, you can use lamda=c/v to get wavelength or E=hv to get energy.

Ziyan Wang 3J

Yes, electrons have its own wavelength and frequency, just as everything, its wavelength is determined by De Broglie equation. But don't mess it up with energy level. After absorbing energy of a photon, the electron jumps to a higher energy level.

Ziyan Wang 3J

(Cu)2+ (aq) + 2(OH)- (aq) ==> Cu(OH)2 (s). Because Na+ and NO3- are always ions, they don't participate in the reaction.

Ziyan Wang 3J

Rydberg equation states that the energy of energy levels equals to hR/n^2 (n=1,2,3...), h is planck constant(6.63*10^-34 Js), R is Rydberg constant (3.29*10^15 Hz)

Ziyan Wang 3J

Thank you!

Ziyan Wang 3J

Does anyone know what will be tested tomorrow? Any topics on quantum world?

Ziyan Wang 3J

Could anyone explain that why decreasing frequency of light leads to the decreasing extent of change of electromagnetic radiation?

Ziyan Wang 3J

H.1 It appears that balancing the chemical equation Cu + SO2-> CuO + S would be simple if we could just add another O atom to the product side: Cu + SO2 -> CuO + S +O. (a) Why is that balancing procedure not allowed? (b) Balance the equation correctly.

Ziyan Wang 3J

Epsom salts consists of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15g? (c) How many moles of water molecules are in 5.15g of Epson salts?

Ziyan Wang 3J

(a) Write the formula for nitric acid. (b) Without doing a calculation, estimate which element in nitric acid occurs with the greater mass percentage.

Ziyan Wang 3J

A molecule of human DNA was found to contain 2.1 * 10^9 atoms of carbon. Calculate the chemical amount (in moles ) of carbon atoms in the molecule of DNA.

Ziyan Wang 3J

E.1 The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144pm, into one of these fibers by encapsulating them in carbon nanotubes. How long would the fiber extend?

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