CHEMISTRY COMMUNITY

Kimberly 1H

Don't forget that in the form ln( $\frac{k_{2}}{k_{1}}$ )=( $\frac{E_{a}}{R}$ ) $(\frac{1}{T_{1}}$ - $\frac{1}{T_{2}}$ )

to use T₁-T₂ not T₂-T₁

Kimberly 1H

In class, Lavelle explained that the frequency factor of H+H-->H₂ is 1 since the electron configuration is 1s, giving it a spherical shape. Are frequency factors solely dependent on orbital shapes?

Kimberly 1H

Use the data in Appendix 2B and the fact that, for the half-reaction F 2 (g)+2H + (aq)+2e - -->2HF(aq), E=3.03 V, to calculate the value of Ka for HF. The answer key shows that you're supposed to take the square root when you find K of the reaction in order to get K a , but I'm not sure I understand...

Kimberly 1H

In the homework section for electrolysis, it's given that the reduction of water:
2H₂O(l)+2e^--->H₂(g)+2OH^- E=-.42V at pH 7
but in appendix B it lists the reduction potential E=-.83.
Am I missing something or is this a typo?

Kimberly 1H

Can someone please explain how elementary reactions relate to reaction mechanisms? And how do the two terms explain the decomposition of O₃ to O₂?

Kimberly 1H

What is the purpose of knowing the overall order of a reaction?

Kimberly 1H

Is the value of K determined by experimental data using the initial rate/molar concentration?

Kimberly 1H

Can someone please explain what the electrochemical series is and what it has to do with a redox couple?

Kimberly 1H

Is the reason why potassium in potassium permanganate and chloride in iron(iii) chloride not included in the balanced redox reaction because they are spectator ions?

Kimberly 1H

Can someone please explain why for part c the answer key says that KOH(aq) is included in the cell diagram?

Kimberly 1H

What are some exceptions/special rules we should memorize for the oxidation numbers of molecules in order to balance the redox reactions?

Kimberly 1H

Can someone please re-explain what Lavelle meant when he said S isn't actually constant but $\Delta$ S is?

Kimberly 1H

I'm not sure I caught what the purpose of these two are.

Kimberly 1H

Would we use the original Van't Hoff Equation: lnK=- $\frac{\Delta H°}{RT}+\frac{\Delta S°}{R}$ for constant temperatures?

Kimberly 1H

Would we use the original Van't Hoff Equation: lnK=- $\frac{\Delta H°}{RT}+\frac{\Delta S°}{R}$ for constant temperatures?

Kimberly 1H

Can someone please explain why we assume $\Delta$ G is 0 when H and S are given?

Kimberly 1H

On the midterm, the last questions asked for the change in entropy of nitrogen gas that went through a change in temperature and volume. Did it matter if we used the C value of an ideal gas or of nitrogen itself?

Kimberly 1H

Why is molar heat capacity of an ideal gas greater at a constant pressure greater than at a constant volume?

Kimberly 1H

What's the difference between heat capacity, specific heat capacity, and molar heat capacity?

Kimberly 1H

Why are bond enthalpies always positive?

Kimberly 1H

How can you tell when to use $\Delta$ U=w vs $\Delta$ U=w+q vs $\Delta$ U=q?

Kimberly 1H

Why does the reversible process do more work than the non-reversible process?

Kimberly 1H

Why can't the total internal energy of a system be measured?

Kimberly 1H

To add onto it, steam condensing to liquid releases over 40 kJ of heat while liquid freezing into a solid releases around 5 kJ of heat.

Kimberly 1H

What's the difference between $\Delta$ H and Q?

Kimberly 1H

When finding the pH of .055M of AlCl₃, the balanced chemical equation shows that there are 6 water molecules attached to Al and the overall charge is +3 on the reactants side. How come it can't be balanced with just 3 water molecules?

Kimberly 1H

What are some examples of superacids and superbases and what makes them have such a high concentration of H₃O⁺ or OH^–?

Kimberly 1H

Consider the activities of pure solids and liquids as 1. Even when you include them in the calculation for equilibrium constant, they doesn't affect the result.

Kimberly 1H

Why don't catalysts affect the equilibrium composition of a reaction mixture?

Kimberly 1H

For values of K which are less than 10^-3, the reaction favors the reactants and for K larger than 10³ a reaction favors the product. But could someone help me clarify what "not strongly favored" means for intermediate values?

Kimberly 1H

In class, there was an example with N₂, H₂, and NH₃. Lavelle explained that taking away the product would increase product yield, but I'm not sure if I understand why.

Kimberly 1H

Why aren't reactants and products in the liquid and solid phases not included when calculating K?

Kimberly 1H

What should we know in order to "describe the chemical properties of amphoteric compounds"? And how would we draw these compounds if they act as both acids and bases?

Kimberly 1H

Is the term "chelating agent" only used to refer to chelates that remove metal ions out of solutions?

Kimberly 1H

Why is it that the TM with an electron configuration of d⁸ have ligands arranged in a square planar configuration?

Kimberly 1H

Does the coordination number also refer to the total number of ligands in a compound and what is the significance of finding the coordination number?

Kimberly 1H

Will we be required to know how to name the compound or is it more important to know what the compound is made up of from the formula for the final? To what extent will this material be tested on the final?

Kimberly 1H

Each hybrid orbital is formed by the linear combinations of x amount of orbitals, but I don't understand the way they're denoted. In the textbook it lists the one of the 3 sp² orbitals as:
h₁= s+2^1/2p_y

Kimberly 1H

Is it impossible to have more than one sigma bond in a set of bonds? Why or why not?

Kimberly 1H

Are dimers, pairs of identical molecules, only be linked by hydrogen bonds? Or can the other intermolecular forces bind them?

Kimberly 1H

The textbook states that intermolecular interactions depending on the inverse 6th power of separation between molecules are considered van der Waal forces, but are they also under the larger umbrella of london forces?

Kimberly 1H

What is the significance of learning about hybridization and sigma vs. pi bonds? Does it affect the chemical or physical properties of the molecule in any way?

Kimberly 1H

Do all see-saw shaped molecules only have one lone pair of electrons?

Kimberly 1H

If the lone pair-lone pair electron repulsions are the strongest, then why can't the two pairs be situated opposite each other, as in a trigonal bipyramidal shape? One lone pair on top and one on the bottom? Wouldn't this result in a molecular geometry of a trigonal planar shape?

Kimberly 1H

Why do polar and nonpolar molecules not mix well, such as oil and water? Does it have to do with having different shapes or dipole/no dipole moments?

Kimberly 1H

How can Schrodinger's equation be used to predict the distortion of a bond angle caused by a lone pair of electrons?

Kimberly 1H

Is a molecule's geometric shape always determined by the degree of its bond angle? And what some examples of molecules whose bond angle are not "fixed by symmetry"?

Kimberly 1H

Why is the correct electron configuration for tungsten: [Xe]4f¹⁴5d⁴6s² instead of [Xe]4f¹⁴5d⁵6s¹? Why shouldn't the d orbital be filled halfway in this instance?

Kimberly 1H

"Broadly speaking, the wavefunction that describes the resonance structure is a more accurate description of the electronic structure of the molecule than the wavefunction for any single structure alone, and the more accurate the wavefunction, the lower the corresponding energy." I have no...

Kimberly 1H

A formal charge of 0 indicates a low energy structure, however the textbook also states that in some cases, the structure with the lowest formal charge is not the most likely. What are some factors that may contribute to this?

Kimberly 1H

The question follows: In an unusual situation, one nitrogen gas molecule is trapped in an alveoli sac. Alveoli are tiny sacs in the lungs whose average diameter is 1.5x10^-4m. Find the uncertainty in velocity of the nitrogen molecule within the sac. I substituted 1.5x10^-4m into the equation for x, ...

Kimberly 1H

I'm not sure I understand why a pair of low energy s-valence electrons being more difficult to remove during ion formation would result in an ion 2 units lower charge than expected.

Kimberly 1H

Are diagonal neighbor elements as similar to properties of elements in the same group?

Kimberly 1H

If it's not possible for 2 electrons to have the same set of quantum numbers, how do parallel electrons exist in the same orbital?

Kimberly 1H

What is the significance of h/4 $\pi$ in Heisenberg's uncertainty equation?

Kimberly 1H

What is the difference between describing a particle by its wavefunction $\psi$ $_{1}$ (and most likely being found in the center of the box) versus $\psi$ $_{2}$ (found in regions between the center and the walls)?

Kimberly 1H

1.25 Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589 nm. How much energy is emitted by (a) an excited sodium atom when it generates a photon; (b) 5.00 mg of sodium atoms emitting light at this wavelength; (c) 1.00 mol of sodium atoms emitting light at this wavelengt...

Kimberly 1H

Why is it that the kinetic energy of ejected electrons increases linearly with the frequency of radiation?

Kimberly 1H

How was this constant empirically derived? Why is it 3.29x10^15 Hz to be exact, and how does it relate to the hydrogen spectrum?

Kimberly 1H

I understand that intensity is the brightness of radiation and you calculate it by squaring the amplitude, but I'm not sure what units these are measured in.

Kimberly 1H

Extensive properties are dependent on size whereas intensive properties are independent of size. For example, mass and volume are affected by size. However, a substance's freezing point, temperature, or density doesn't change with size.

Kimberly 1H

Yes, the 2 represents the ratio of product that can be formed. In order to find out how much product you end up with, you multiply the ratio of product:reactant, in this case, 2:3.

Kimberly 1H

I'm not sure how to start solving this problem: In medicine, it is sometimes necessary to prepare solutions with a specific concentration of a given ion. A lab technician has made up a 100.0-mL solution containing 0.50 g of NaCl and 0.30 g of KCl, as well as glucose and other sugars. What is the con...

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