CHEMISTRY COMMUNITY

Katie_Duong_1D

Katie_Duong_1D wrote:can someone please explain how to get the equilibrium constant for 1d in Gibbs free energy/worksheet 6? I keep getting 1.014.

I forgot to convert delta G from kj/mol to j/mol to match units. Now I get the correct answer 1.663 x 10^6.

Katie_Duong_1D

can someone please explain how to get the equilibrium constant for 1d in Gibbs free energy/worksheet 6? I keep getting 1.014.

Katie_Duong_1D

How do you get the largest E cell? Standard reduction potentials are given for a set of species.

Katie_Duong_1D

What is the trend for increasing reducing power/increasing oxidizing power? How can you tell by looking at standard reduction potentials?

Katie_Duong_1D

The graph looks like a horizontal asymptote at equilibrium. This is because the concentration flattens at equilibrium.

Katie_Duong_1D

You include H+, OH-, and water when balancing equations, then cancel if they are on both sides. H2O is a pure liquid, so only include aqueous OH- and H+ are included.

Katie_Duong_1D

The more negative a reduction potential is, the stronger the reducing agent. The less negative/more positive a reduction potential is, the stronger the oxidizing agent.

Katie_Duong_1D

A unique rate is the rate of appearance/disappearance of a chemical species, divided by the stoichiometric coefficients. The unique rate changes over time as the reaction continues.

Katie_Duong_1D

n is the change in moles in the balanced redox reaction. For example, if one side has 22 electrons and the other side has 25 electrons, n = 3.

Katie_Duong_1D

The salt bridge allows for ion transfer between the anode and cathode.

Katie_Duong_1D

2Cl- means that the -1 charge of Cl- is multiplied by 2.

Katie_Duong_1D

Gibb's free energy is the energy available to do work. delta g = delta h - t*delta s. A negative delta G means the reaction is spontaneous. we do not have to worry about it yet; it is not on the midterm.

Katie_Duong_1D

The midterm covers everything up to before Gibb's free energy!

so acids and bases, equilibrium, thermodynamics (1st, 2nd, 3rd laws)

Katie_Duong_1D

A cup of tea is an open system because energy and matter can exchange with the surroundings. You can add more/less tea (matter), and tea can become hotter/colder (energy).

That's the tea, sis

Katie_Duong_1D

We are fully in the thermochemistry unit of the class. These are the homework problems for this unit, pasted from the syllabus: 7th Edition: Focus 4A-4D.5; 4E3 Problems4A:1,3,5,7,9,11,13; 4B:1,3,5,7,9,13; 4C:1,3,7,9,11,13,15;4D:1,3,5,7,9,11, 15, 17, 19, 21, 23; 4E: 5, 7, 9; and 4.1, 4.5, 4.7, 4.15, ...

Katie_Duong_1D

I think of heat as a form of energy (thermal energy). However, energy can be more than just heat (e.g. work)

Katie_Duong_1D

The heating curve of water has heat absorbed on the horizontal axis and temperature on the vertical axis. There is a steep slope from solid to melting; the horizontal line for melting is the shortest because it takes the least energy to change from solid to liquid phase. The slope from 0 to 100 degr...

Katie_Duong_1D

An inert gas has no effect on the reaction because partial pressures of reacting gases stay the same.

Katie_Duong_1D

The heat being used to change phases is only used to break the bonds because it takes a lot of energy to do so. This is shown by the horizontal line on the water heating curve. Temperature only increases during solid, liquid, and gas phases.

Katie_Duong_1D

You can calculate Q exactly how you would calculate K. Q = [products]/[reactants]. If Q<K, the reaction shifts right to reach equilibrium. If Q = K, the reaction is at equilibrium. If Q >K, the reaction shifts left.

Katie_Duong_1D

An endothermic reaction is when delta H is positive and energy is absorbed, so the surroundings cool. An exothermic reaction is when delta H is negative and energy is released, so the surroundings are warm. Applying Le Chatelier's principle, if heat is added to an endothermic reaction, the reaction ...

Katie_Duong_1D

pH is -log(H3O+ concentration). pka is -log(ka).

H3O+ concentration can be calculated by "undoing" the log. 10^-pH. From there, you can do an ICE table to find ka. ka is equilibrium concentrations for products over equilibrium concentrations for reactants.

Katie_Duong_1D

Q is the reaction quotient. K is the equilibrium constant. Q can be calculated at anytime during the reaction, while k is only at equilibrium. If Q<K, then the reaction shifts right to reach equilibrium. If Q>K, then the reaction shifts left to reach equilibrium.

Katie_Duong_1D

Adding an inert gas has no effect because the partial pressures remain the same, so the system is still at equilibrium. If you reduce volume, that increases pressure according to the ideal gas law, PV = nRT. To determine whether the system shifts left or right, first determine whether there are more...

Katie_Duong_1D

Le Chatelier's principle states that there is a tendency for systems in equilibrium to shift left or right to return back to its normal state. A decrease in SO3 would cause amounts of NO to increase because SO3 is a product like NO. If a product is decreased, then the forward reaction is preferred t...

Katie_Duong_1D

kp = kc (RT)^ ((c+d) - (a+b)).
c+d - a+b is also known as delta n

The equilibrium constant for pressure is equal to the equilibrium constant for concentration times (gas constant R times temperature T (in K)) to the power of the mole change.

Katie_Duong_1D

Live Love Lavelle <3 Thanks for being the most caring and wholesome teacher! Your smile at the beginning of each class made my days. I always looked forward to your informative and interesting lectures. I really appreciate all the work that went into organizing many office hours, workshops, and 24/7...

Katie_Duong_1D

Why can it only occur with N O and F? Hydrogen bonding only occurs with N O F because these are very electronegative elements. N O F have more electron pulling power, creating a partial positive on the hydrogen and a partial negative on N O F. The electrostatic attraction between H and N O F is str...

Katie_Duong_1D

Yes, I think this is a possible question. Finding concentration from pH is basically undoing the log. concentration = 10^-pH

Katie_Duong_1D

CH2O is trigonal planar, AX3, so there are 3 regions electron density. Hybridization regions = regions of electron density, so there are 3 hybridization regions. This corresponds with sp2.

Katie_Duong_1D

Both are correct. However, Lavelle has a personal preference for sp3d because it looks more uniform when listed with other hybridizations (sp, sp2, sp3, sp3d2)

Katie_Duong_1D

AX2E2 would have a bond angle of less than 109.5 degrees. A molecule with this VSEPR formula has 4 regions of electron density: 2 shared and 2 lone pairs. The electron geometry is tetrahedral, but the molecular geometry is bent because the 2 lone pairs on the central atom would slightly bring the at...

Katie_Duong_1D

Any element period 3 and below can have an expanded octet because they can also have d orbitals (10 valence electrons). For example, Phosphorus can have an expanded octet because it is in period 3, while Nitrogen cannot have an expanded octet because it is in period 2.

Katie_Duong_1D

The number of electron densities should equal the number of sigma pi bonds. If there are 4 regions of electron density (AX4, for example), then the sp hybridization would be sp3.

Katie_Duong_1D

An ion is any atom with a nonzero charge. A positive ion is a cation. A negative ion is an anion. You would use ion in naming if the atom or compound is nonzero in charge.

Katie_Duong_1D

Hydrogen bonds and covalent bonds can happen at the same time because hydrogen bonds are within the same molecule (H with N,O,F) whereas covalent bonds are nonionic bonds between different molecules.

Katie_Duong_1D

Can an octahedral also be classified as square bipyramidal? In the same way that a trigonal bipyramidal is named fittingly for its shape, couldn't an octahedral be named this? The octahedral shape corresponds to VSEPR formula AX6, meaning there are 6 bonding regions. However, the name is octahedral...

Katie_Duong_1D

If there are 5 regions of electron density, hybridization is sp3d. If there are 6 regions of electron density, hybridization is sp3d2.

Katie_Duong_1D

Molecular geometry does not consider lone pairs as areas of electron density. An example would be a molecule with VSEPR formula AX4E2. There are 6 bonding regions, 4 bonding pairs and 2 lone pairs. AX4E2 is square planar (molecular geometry). The electron geometry of this molecule would be octahedra...

Katie_Duong_1D

XeF4 has a molecular geometry of square planar (AX4E2) because there are 4 bonding pairs and 2 lone pairs on the Xe central atom. XeF4 has an electron geometry of octahedral (AX6) because there are 6 bonding regions. AX6 is called octahedral because an octahedron has eight faces.

Katie_Duong_1D

Be is an exception to the octet rule; it only needs has 2 valence electrons. Since Be bonds with Cl on both sides, it already has 2 valence electrons, so there is no need for additional lone pairs on the Be. BeCl2 is AX2 and linear.

Katie_Duong_1D

delta v would be 10 because that Is the entire spread of uncertainty in velocity. +- 5 means that the uncertainty in velvety is to a magnitude of 5 in both directions.

Katie_Duong_1D

Atoms in period 3 and greater can have an expanded octet (more than 8 valence electrons) because they also have d and f sub shells, so the can accommodate more than 8 electrons.

Katie_Duong_1D

H20 has hydrogen bonding and the bond length is short, so it takes more energy to break the bonds. H2S is not hydrogen bonding and the bond length is longer, so it takes less energy to break the bonds.

Katie_Duong_1D

VSEPR stands for valence shell electron pair repulsion. Electrons are negatively charged, so they do not want to be near each other. The Lewis structure and AXE notation of a molecule can determine its best molecular shape.

For example, AX3 is trigonal planar. The bond angle is 120 degrees.

Katie_Duong_1D

It is much easier to do Lewis structure of glycine if you memorize the basic structure of an amino acid. There is a central carbon; there is an R group (just another H in this example) bonded on top and another H bonded on the bottom. One side of the central carbon is an amino group (NH2), with N b...

Katie_Duong_1D

It is much easier to do Lewis structure of glycine if you memorize the basic structure of an amino acid. There is a central carbon; there is an R group (just another H in this example) bonded on top and another H bonded on the bottom. One side of the central carbon is an amino group (NH2), with N bo...

Katie_Duong_1D

Electrons in the outer shells are the first to go. The first 3 electrons to go in In would be 1 electron in 5p1 and 2 electrons in 5s2 because they are farther away from the nucleus.

With this three electrons gone, In3+ = [Kr]4d10

Katie_Duong_1D

Hello! For question 3, I keep getting 37.2 g NO for my answer, not 31.7g NO. Is this an error in the solutions, or did I do something wrong? Equation: 4NH3 + 5O2 --> 4NO + 6H2O (21.1 g NH3/17.04 g/mol NH3) x (4 mol NO/4 mol NH3) (30.01 g/mol NO) = 37.16 g NO, rounded to 37.2 g NO. Please let me kno...

Katie_Duong_1D

Hello! For question 3, I keep getting 37.2 g NO for my answer, not 31.7g NO. Is this an error in the solutions, or did I do something wrong? Equation: 4NH3 + 5O2 --> 4NO + 6H2O (21.1 g NH3/17.04 g/mol NH3) x (4 mol NO/4 mol NH3) (30.01 g/mol NO) = 37.16 g NO, rounded to 37.2 g NO. Please let me know...

Katie_Duong_1D

All the released midterm exams in the old course reader show free response questions. Professor Lavelle said there would be 8 questions in total, with multiple parts to each big question. Calculations are the biggest component, but there should also be some conceptual questions.

Katie_Duong_1D

l = n-1 refers to the max value of l. This means that the value of l can be lower than n-1, but not higher. For example, the 3p orbital is n=3 and l=1. The l value can either be 0, 1, or 2. Since n=3, l max is l=3-1=2, so for n=3,the possible orbitals are 3s, 3p, 3d.

Katie_Duong_1D

The atom with the lowest ionization energy should be the central atom. Since C has the lowest ionization energy, it should be the central atom. Carbon is also tetravalent, so being the central atom makes it easier for carbon to get its four bonds.

Katie_Duong_1D

Resonance structures are a "blend" of all the different ways a certain molecule can bond together. Resonance structure have the same overall charge and composition, but the formal charges of each constituent atom may be different.

Katie_Duong_1D

The octet rule is a guideline that atoms have 8 electrons surrounding it. However, there are exceptions to this rule.

Katie_Duong_1D

Hi Haley! An ionic bond is between a cation (nonmetals) and an anion (metals). Positive and negative ions attract each other and form an ionic bond; nonmetals are stronger and get electrons from the metal. A covalent bond is between two electromagnetically similar nonmetals. Neither nonmetal is stro...

Katie_Duong_1D

Electron affinity has a less periodic trend (i.e. no rule for increasing across period/going down a group). Generally, high electron affinity elements are in the top right of the periodic table.

Katie_Duong_1D

Each electron has a -1 charge. Cations are made when electrons are removed from atoms.

To get copper (I), remove 1 electron. For copper (II), remove 2 electrons.

Katie_Duong_1D

In sub shell notation, n refers to the coefficient. For example, a. n = 5, l = 2 would be 5d. This is because n=5, so the coefficient would be 5, and l = 2 corresponds with d. There are 5 possible electrons with that quantum number because l=2, so the possible electrons would be -l and +1 (-2, -1, 0...

Katie_Duong_1D

In a Balmer series, n1=2 and n2=7. We can find n2 by using the equation V = R(1/n1^2 - 1/n2^2). V = 3.29 x 10^29 Hz (Rydberg's constant) x (1/4 - 1/39) = 7.55 x 10^14 Hz. Then we can plug v into c = lambda x v and solve for lambda to find wavelength. lambda = c/v = (3.00 x 10^8 m/s)/(7.55 x 10^14 s^...

Katie_Duong_1D

A nodal plane is a region with zero probability of electron density (no electrons). The s orbital is spherical and has no nodal planes The p orbital has 2 lobes on either side of the nucleus and there is a nodal plane. The d orbital has nodal planes. 3 shapes have 4 lobes along the xy-yz-zx planes. ...

Katie_Duong_1D

l, orbital angular momentum, shows the shape. l = n-1.

l values also correspond to an orbital shell.

l=0 is s
l=1 is p
l=2 is d
l=3 is f

Katie_Duong_1D

All elements emit a different wavelength. Analysis of a specific wavelength can help identify the element because each element because the specific wavelength might only correspond to one specific element. For example, hydrogen has three lines with wavelengths of 434 nm, 486 nm, and 656 nm.

Katie_Duong_1D

Robert Millikan could not measure a single quantum of charge; that value is too small. Instead, he measured the charges of many oil drops, then noticed a pattern in the charge value. He realized that all these values were divisible by 1.602 10−19 coulomb, a single unit of charge. positive charge = 1...

Katie_Duong_1D

Hello Sydney! 1 Hertz (Hz) is a SI derived unit to measure frequency. 1 Hz is equal to 1 cycle per second (1 cycle/1s). S^-1 is equal to 1/s because a negative exponent is a division. The unit s^-1 makes more sense in the context of c (m/s) = wavelength (m) x frequency (s^-1) because the units on th...

Katie_Duong_1D

The most basic combustion reactions involve a hydrocarbon and oxygen to create water and carbon dioxide. In this case, oxygen is the oxidant. Example H1 asks to balance the combustion reaction of C6H14. I would start off with C6H14 + O2 --> H2O + CO2. From there, balance the carbons; since there are...

Katie_Duong_1D

Molarity (M) represents moles of solute (mol) per volume of solution (L). M = mol/L. Because molarity is expressed in terms of moles and liters, it is much easier to keep units consistent, so you can cancel out units when cross multiplying. If the volume is given in millimeters (mL), I would convert...

Katie_Duong_1D

Hello! g/mol and g * mol^-1 mean the same thing. They are just written out a little differently. g/mol is dividing unit mass (g) by unit mole (mol). g * mol^-1 is also a division, but written as a multiplication. Mol is raised to the power of -1, so mol is treated as a denominator. I personally like...

Katie_Duong_1D

You: Laurence Lavelle
Me, an intellectual: Lawrencium (Lr) LaVelveetaCheese

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