CHEMISTRY COMMUNITY

Anne Tsai 1F

Yes, the product has a -1 charge overall.

Anne Tsai 1F

Both oxygens and and the chlorine will be attached to sulfur. One of the oxygens will have a double bond, and the other one will have a formal charge of -1.

Anne Tsai 1F

Professor Lavelle posted this pdf on his website with all of the ligands and their names on his website: https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf

Anne Tsai 1F

Amphoteric means that the substance can act as an acid or base, but amphoprotic means that the substance can donate or accept H+. Amphoprotic substances must have both a lone pair and at least one hydrogen.

Anne Tsai 1F

I believe this is J.12. I think the correct image should be the one with most of the bonds still present; in weak acids, only a small fraction of the HF is deprotonated.

Anne Tsai 1F

I'm not entirely sure, but maybe bisoxalato comes first because C2O4 comes before OH2 in the alphabet. I read older posts on this problem that suggest the parentheses are there to separate water from the other ligands.

Anne Tsai 1F

The ligands should be written in alphabetical order disregarding their prefixes, so I think NH3 should be written first.

Anne Tsai 1F

The outline says "Know the types of hybridization (sp, sp2, sp3, sp3d, sp3d2) and apply this bonding model to inorganic, organic, and biological compounds (molecules, cations, and anions)" and "Describe the structure of a molecule, cation, or anion in terms of hybrid orbitals and sigm...

Anne Tsai 1F

Hybridized orbitals are used to explain the geometric shapes of molecules by combining orbitals into hybridized orbitals (sp, sp^2, sp^3, etc). I found this pdf that might explain it better: http://www.chem.ucla.edu/~harding/notes ... als_01.pdf.

Anne Tsai 1F

When a polydentate ligand binds to a metal with 2 different bonds, it forms a chelating complex, so the NH2 molecules need to be close enough in proximity in order to both bind with a central atom.

Anne Tsai 1F

Coordination compounds are biologically important for catalyzing chemical reactions.

Anne Tsai 1F

A chelate is a coordination compound formed by at least two bonds between ligand and a central metal, resulting in a ring structure.

Anne Tsai 1F

Cisplatin binds to two guanine bases in DNA, allowing a HMG protein to bind and insert a phenyl group into the DNA, which creates a kink in the DNA and causes the cell to die instead of divide.

Anne Tsai 1F

Polydentate ligands are chelating agents with multiple atoms bound to a metal in a coordination complex.

Anne Tsai 1F

I believe it's Bis(2-aminoethyl)amine.

Anne Tsai 1F

You would have to be given an electronegativity table to know the exact electronegativities of each atom, but generally you can follow the periodic trend (electronegativity increases across a row and decreases down a group).

Anne Tsai 1F

I think XeF2 is nonpolar because the fluorines are arranged so that the molecule has a linear shape, and thus there is no dipole moments.

Anne Tsai 1F

The shape of the molecule is tetrahedral, and the chlorine molecules aren't exactly opposite each other (you can search a picture to see), so the dipoles don't cancel out.

Anne Tsai 1F

Although C and F have the larger difference in electronegativity, CHI3 is simply larger, so it has a higher boiling point.

Anne Tsai 1F

CH2Cl2 has a tetrahedral shape, so I believe the dipoles on the C-Cl bonds don't cancel out.

Anne Tsai 1F

I think polarity is determined by the difference in electronegativities between atoms in a molecule. However, symmetry does play a role with a molecule like CO2, which is nonpolar overall despite the charge differences between C and O because the oxygens pull on the carbon in the center equally and ...

Anne Tsai 1F

In LS7A, there's a distinction between temporary dipole moments in van der Waals forces and permanent dipole moments in polar covalent molecules. Does the same apply to chemistry or are they equally grouped under dipole interactions?

Anne Tsai 1F

Yes, this structure would be amphipathic, meaning it is only partially polar where, say, the partially negative oxygen is. The hydrogen would be bound to an atom that is not very electronegative, like carbon.

Anne Tsai 1F

A dipole describes the separation of charges between 2 bonded atoms.

Anne Tsai 1F

Dipole arrows are drawn when there is a difference in electronegativity between atoms in a molecule, and the arrow is pointing towards the more electronegative atom.

Anne Tsai 1F

The de Broglie equation is used for any particle with momentum and wave-like properties.

Anne Tsai 1F

Yes, it's essentially Hund's and Pauli's rules with the additional statement that electrons are added in order of increasing energy.

Anne Tsai 1F

Can someone explain how the UAs suggested to quickly calculate formal charge by drawing a circle and counting lines and dots? And does it work for all Lewis structures?

Anne Tsai 1F

I have trouble with drawing Lewis structures too, but I recall the UAs saying that the order we should follow is:

1. electrons
2. octet rule
3. formal charge

Anne Tsai 1F

During the review session on Friday, the final Lewis structure for ClO4- had double bonds between 3 of the oxygens and Cl but a single bond for one of the oxygens. Why is that and what does it have to do with formal charge?

Anne Tsai 1F

What is the difference between electronegativity and electron affinity, and do they differ in their periodic trends?

Anne Tsai 1F

Because n=2, l can equal 0 or 1. If l=0, then ml=0. If l=1, then ml can equal -1, 0, or 1. In total there are 4 possible orbitals.

Anne Tsai 1F

If you want to see the number of orbitals per subshell visually, you can count the number of elements in one row of a block on the periodic table, then divide that number by 2 because each orbital holds a maximum of 2 electrons.

Anne Tsai 1F

In the d subshell, having a full (d^10) or half full (d^5) subshell is more stable, so for chromium, instead of the electron configuration being [Ar]3d^4 4s^2, one electron in the p subshell rises to the d subshell, making the electron configuration [Ar]3d^5 4s^1. The same goes for copper, but inste...

Anne Tsai 1F

Someone has asked about this already, but I still don't understand how a structure can be a blend of multiple structures. Does it mean that a structure is constantly alternating between all of its possible arrangements?

Anne Tsai 1F

For part c, the question is asking how many orbitals can have a quantum number of n=2. Does this mean to find the sum of all of the possible values for ml if l can equal 0 or 1?

Anne Tsai 1F

You should have gotten 3.37 x 10^-19 J as your answer for part a when calculating the energy of one sodium atom, which you then use to convert to grams and moles in parts b and c.

Anne Tsai 1F

Part a is asking you to convert wavelength to energy. Part b is asking you to take that calculated energy (which is in joules per atom) and convert that into joules per gram, and part c is asking for joules per mole.

Anne Tsai 1F

We know that we are solving for uncertainty in speed, so we rearrange the uncertainty equation in terms of delta v. H bar and the mass of an electron are given values, and delta x is 350 pm or 350 x 10^-12 m because we know that the electron must be traveling within the diameter of the atom. If you ...

Anne Tsai 1F

But the problem asks for the minimum indeterminancy, so why don't you use 5 m/s in your calculation?

Anne Tsai 1F

The mass of an electron is always 9.109 x 10^-31 kg.

Anne Tsai 1F

Frequency is the number of cycles per second, while intensity refers to the number of photons.

Anne Tsai 1F

Another way to think about it is that lines in the Lyman series represent an electron transitioning from an energy of n≥2 to n=1, and that lines in the Balmer series represent an electron transitioning from an energy of n≥3 to n=2.

Anne Tsai 1F

Solve for the frequency by dividing the speed of light by 102.6 nm (converted into meters). Then, using Rydberg's equation, solve for the final energy level (n2) knowing that n1 = 1 because the spectral line is observed in the UV region.

Anne Tsai 1F

The Paschen and Brackett series are in the infrared region.

Anne Tsai 1F

Yes, you would assume that your sample is 100 g, but to convert to moles, you actually have to divide by the molar mass of each element as found on the periodic table (so 12.01 g/mol for C). You don't need to divide 63.15 by 100 because if you assume the sample is 100 g, then 63.15% of 100 would jus...

Anne Tsai 1F

For E21a) in particular, you're converting 0.0981 moles of Al2O3 into molecules because Al2O3 is a molecular compound. If you were dealing with an element, however, like Al, you would be converting into atoms. In both cases though, you would use Avogadro's number to convert.

Anne Tsai 1F

For part b, 55.49 is the number of moles, not the number of molecules in 1000 g of water. To get the number of molecules, you have to multiply by 6.022 x 10^23 molecules per mole, which should equal 3.34 x 10^25 molecules.

Anne Tsai 1F

AKatukota wrote:So formula units just means atoms?

It depends on the problem; formula units is used to describe the mass per mole of an ionic compound, while atoms is used to describe the mass per mole of an element.

Anne Tsai 1F

When you need to use a stoichiometric coefficient that is not a whole number, you can write it as an improper fraction (such as 5/4). Then you will know to multiply the whole equation by the denominator (in this case 4) to get the lowest whole number.

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