CHEMISTRY COMMUNITY

Trinity Vu 1D

Whenever a molecule has a pi bond, only look at the number of bonding regions in order to determine hybridization. This means that even though there may be 4 bonds, 2 single and 1 double, there are still only 3 binding sites and therefore you only need a sp2 hybridization not a sp3 hybridization. Th...

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The ligand names go alphabetically before the transition metal atom/ion. However when writing the chemical formula, remember to write the metal first since cations are named before anions.

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They're not always on "the right side" of the chemical equation because in an equilibrium equation the reaction goes both "forward" and "backwards" so reactants become products which become reactants etc. The conjugate bases and acids are always opposite from their corr...

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In order to calculate pH you use the concentration of hydronium. Therefore you need to divide mol H3O by L of solution which will give you .025 M H3O. Same for (b) You divide the .005 mol H30 by .250L in order to get the new concentration ([H3O] which gives you .02. Then you can take the -log of thi...

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This is because they refer to the same thing in a chemical equation. When AH dissociates to A- and H+ the H+ ions form bonds with the partially negative O in H2O to form H3O. Its written as [H+] as a shorthand.

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You determine whether or not a ligand is polydentate by identifying how many donor atoms/lewis base sites can be used to bond to a singular central atom. For example H2O is monodentate because it only has 1 binding site (the O atom) in which it can bond to a central atom because H cannot form anothe...

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Even though there are 4 o atoms which would be 4 binding sites, because of the molecular shape of the oxalate molecule, a single metal atom can only bond with 2 o atoms max. The 4 o atoms can form 4 bonds to metal atoms, just not all with the same singular central metal atom.

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Since hybridization only happens when an atom is bonded to multiple other atoms, hydrogen itself is never hybridized because it can only form 1 bond since it only has a 1s orbital.

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Stereoisomers are molecules that have the same formula and bonded atom sequences but have different orientations/arrangements. An example of this would be the trans-2-butane and cis-2-butane examples we went over in lecture. They have the same formula C4H8 and same bonded atom sequences but differen...

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It's a coordinate covalent bond because o2- provides both of the electrons in the electron pair that forms the bond between the o2- atom and the h+ atom. This is because since it's H+ this means that the H atom doesn't have any electrons to "share" with the o2- atom.

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An acid/base is considered strong or weak depending on whether or not it completely ionizes in a solution/water. One way to know is there was a 100% dissociation for an acid for example is by looking at the Ka value. Whenever the Ka is given you can generally assume its a weak acid because this mean...

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Its written as OH2 because depending on the location of the molecule when it is acting as a ligand, the position of the water molecule changes. When a water molecule is a ligand on the right side of the central transition metal atom, the O is what bonds to the central atom, not the H2. Therefore, wh...

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How do you know which orbitals/how many orbitals mix and hybridize for an atom in a molecule? For example, in class we went over CH4 in which C has sp3 orbitals while C2H4 has sp2 orbitals.

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Why are chelating ligands able to bind cations tightly? Does it have something to do with the ring structure?

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Also, transition metals are often the central atom of these coordination compounds because since they have multiple oxidation states, they can easily accept electron pairs thus making them good for electron transfer.

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Also, an example would be a chelate that only has single bonds (sigma bonds) ie NH2CH2CH2NH2 meaning it's flexible and can rotate. Thus it's able to form a ring even though NH2CH2CH2NH2 by itself wouldn't be ring shaped.

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To determine whether something has hydrogen bonds, draw out the lewis structures. Even though C2H5OC2H5 has O and H, none of the H are bonded to the O and therefore cannot form hydrogen bonds.

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Adding on, an example of this distortion as a result of repulsion strength is SO3 2-. Even though S is trigonal pyramidal which has bond angles of 109.5, since there is a lone pair on S, the lone pair exerts repulsion on and pushes down the bonding electrons of the O atoms. Thus the actual O-S-O bon...

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Whenever there is no central atom, you look at the regional shape of each part of the molecule to determine the overall shape. If you look a each region of C2H4 with each C being the central atom of its respective region, both have trigonal planar shapes. Thus the overall molecule's shape is trigona...

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The tetrahedral bond angles become distorted when the central atom has lone pair(s) of electrons. Since the repulsion strength between a lone [air and bonding pair of electrons is greater than bonding-bonding pairs, the lone pair of electrons force the bonding electrons closer together. Thus the bon...

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Dipole-induced dipole interactions occur when a molecule with an induced dipole interacts with a molecule that has a permanent dipole. For example, H2O has a permanent dipole with H being partially positive and O being partially negative. O2 on the other hand in non polar and has induced dipole inte...

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You look for if the molecule can have dipole moments based on the difference of electronegativity between the two atoms. Electronegativity increases across and up the table. However, beware that a molecule can be overall non polar but still have polar bonds. This is because, for example, in a CO2 mo...

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why do boiling points play a role in the forces? Its the other way around. Forces play a role in determining boiling points because different forces have different strengths and thus require more or less energy to break. AsF3 has a higher boiling point because it has dipole-dipole forces while AsF5...

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Dipole-dipole forces is an interaction between two polar covalent molecules such as HF. London dispersion forces are temporary induced dipole interactions that happen between non polar covalent molecules as the electron distribution fluctuates leaving one side of the molecule with more electrons and...

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Polarizability increases the molecule size increases because this means that the electron shells increase and therefore the size of the electron cloud increases. The valence electrons get further away from the nucleus and experience weaker effective nuclear charge thus making them more easily distor...

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Hydrogen bonding is much stronger than dipole-dipole forces and London forces. London forces are the weakest because they are only temporary induced dipole interactions.

Trinity Vu 1D

For part b, although C and Br have an electronegativity difference of about .45, because since C is surrounded by Br atoms and doesn't have any lone pairs, the partially negatively charged Br atoms of other CBr4 molecules cannot have dipole interactions with it. Only the Br molecules have lone pairs...

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What does it mean for a bond to have ionic character and covalent character? For example, C-F and C-Br are both covalent bonds but question 2b on mini Dino nuggets review packet asks which has more ionic character. Is this referring to dipole moment magnitudes? If so, what would covalent character m...

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The answer is [Ar]3d10 because even though the 4s block on the periodic table is seen before the 3d block, 3d is still a shell below 4s and therefor the 3d shell would fill up before you could add any electrons to the 4s orbital. Because Cu+ has 28 valence electrons and you know that it comes after ...

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Yes because +- 3 means that the actual speed can be anywhere from 55 to 61 which is a range of 6. Multiplying by 2 allows you to take into account the + and the -.

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Two atoms will have a longer bond when their electron density region is bigger because due to electron repulsion between the two density clouds, the atoms cannot get as close to one another as opposed to if the density clouds were smaller. Since the atoms can't get as close, the bond length increases.

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This means that the electrons are not fixed to one specific position/atom. For example, in resonance structures, one structure can have a single bond between atoms A and B and a double bond between B and C. However, in another structure, there's a double and between A and B and a single bond between...

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You can see which electrons are delocalized based on the bond pairs are delocalized. These are the bonds that aren't fixed to a specific location and can be drawn in different locations when you draw out the resonance structures.

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Delocalization refers to how electrons in molecules, ions, etc. and thus covalent bonds aren't associated with and limited to a single specific arrangement. This is seen in resonance structures where the covalent bonds are in different positions.

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Delocalized refers to the electrons in a molecule, ion, etc. that aren't associated with and "stuck to" a single specific atom or covalent bond and can have different arrangements. These delocalized electrons result in resonance (ie the benzene example went over in lecture where there are ...

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Shells are divided into sub shells based on the l number and sub shells are further divided into orbitals. For example the shell n=2 can have sub shells l=0 which is 2s and l=1 which is 2p. 2s and 2p are further divided into orbitals which is where electrons can be paired up. For example, 2p orbital...

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Another way to figure out excited vs ground state is if you look at the drawn out electron configuration (the one with the arrows ie its given in some of the book problems) and see if if each orbital in a sub shell contains an electron before electrons begin pairing or if a sub shell orbital (ie 3s)...

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In order to find the kinetic energy of the ejected electron you would use the equation Ek=1/2mv^2 in which m is the mass of an electron (which you can look up on the constants sheet) and v is the given velocity of the electron.

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Since the wavelength of the light is 1850 nm, you can find energy per photon by using the equations E=hv and c=vλ to get the equation E=hc/λ. Plug in the wavelength, constants, and solve to get energy per photon. Since the answer is energy per photon and the bulb emits 11J of energy, divide 11J by #...

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I think it just refers to how you think about the space the electron has to travel in the atom. It's easier to think about it as 1 dimensional because then you only have to think about the uncertainty of position within one plane rather than the three dimensional plane that would involve x, y, and z...

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Those two equations are for electromagnetic radiation (light/photons). You'd use the equations λ=h/p and Δp*Δx≥h/4π for particles ie electrons. This is because particles like electrons have mass whereas photons don't.

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You use different equations depending on if you are calculating values for photons (electromagnetic radiation/light) or particles (ie electrons). Particles have mass whereas photons don't. You would use equations 1 and 2 for photons/electromagnetic radiation calculations (you can also tell because b...

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102.6 nm is the wavelength of the incoming light which can be used to find the frequency of the light. In order to find the energy values of the levels, you use the Rydberg equation En=-hR/n^2. Using this equation and v=ΔE/h you can rearrange the equations to get v=-R[1/n1^2-1/n2^2]. Since the UV re...

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This is because DeBroglie equation refers to moving particles such as a car or an electron. However, light is electromagnetic radiation and therefore you could only apply the electromagnetic equations λv=c and E=hv to photons.

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By using the given wavelength, you can calculate the energy per photon (E=hv and c=vλ). Since the lamp is 32W which means 32 J/s, you know that in 2 seconds the lamp will generate 64 J. Divide 64J by the calculated energy per photon in order to find how many photons are emitted.

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A. You have to balance the equation equations first. Then, convert P4 and O2 into moles. Using those moles you can determine which reactant is the limiting reactant (in this case its O2 because there's .04657 mol P4 which requires .1397 mol O2 to react (since the balanced equation is P4 + 3O2 --> P4...

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You would need to find how many moles of CuSO4 are needed to make the .2M solution. Then using that number of moles you would multiply by the molar mass of CuSO4 5H20 instead of the molar mass of just CuSO4. From part (a) since you know that you need .05 moles of CuSO4, you'd multiply .05 by 249.68g...

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Adding on, increasing the intensity of the light shined on the metal doesn't affect the kinetic energy because the kinetic energy is in regards to the kinetic energy per electron released not total kinetic energy. Increasing the intensity of the light would mean increasing the number of photons and ...

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In order to find how many moles of product is created based on the moles of the limiting reagent, you would first need to make sure the equation is balanced. You would use the stoichiometric coefficients in the balanced equation as the ratio of moles used/produced relative to other reactants and pro...

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You should always save using sig figs for when you get your final answer instead of during calculations. For example, if you had to convert 5.63 g O2 to moles and then to atoms, you would put the answer in 3 sig figs but you wouldn't put the mid-calculation, the moles, in sig figs (just use the exac...

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You should always use as many digits as possible, so 1.008 g H for example, when doing calculations and save rounding for sig figs for when you have your final answer because if you round/use signings prematurely while you're still doing calculations it can affect your final answer. It wouldn't affe...

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Since you've already balanced the equation, you know that for every mole of PCl3 that reacts with an excess amount of water, 3 moles of HCL will be produced. Therefore you would convert 23.6 g PCl3 to mole and multiply that by 3 because that will be how many moles of HCl will be produced. Then you c...

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Unless the numerical value is explicitly stated in the problem and given to you, you don't consider the constant when figuring out how many sig figs to use. This is because, for example, 12.01g/mol C on the periodic table is not an exact measure of the exact number of grams in 1 mole of carbon. It's...

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