CHEMISTRY COMMUNITY

Norman Dis4C

A catalyst is used up and formed or stays intact throughout the reaction.

Norman Dis4C

More molecules have enough kinetic energy, so more collisions happen.

Norman Dis4C

A catalyst is used up and formed and an intermediate is formed and used up.

Norman Dis4C

Does it change with temperature though?

Norman Dis4C

Homogenous catalysts are used up and formed, but heterogeneous is not since the reactants and catalysts are in different states.

Norman Dis4C

Can someone derive this equation for me? Why does K=kforward/kreverse?

Norman Dis4C

They are not part of the overall rate law but the elementary steps.

Norman Dis4C

I believe pressure changes could also induce temperature changes, which indirectly changes K.

Norman Dis4C

I think Dr.Lavelle said we need to explain the mechanisms from its rate of formation but not propose one.

Norman Dis4C

The rate law of formation depends on the slowest reaction, in this case, the first reaction.

Norman Dis4C

For this question, you are just finding the rate of formation for the listed substance, which is the coefficient times the unique rate.

Norman Dis4C

Remember to add a negative sign of the part of the reactant as we always want positive value for rates.

Norman Dis4C

Always use the standard unit if not specified by the problem.

Norman Dis4C

I don't remember Dr.Lavelle saying anything about using units to determine the order, but this seems like a pretty useful approach.

Norman Dis4C

It's essentially the order of the reaction that is determined by the concentration of reactants.

Norman Dis4C

In this reaction, the C and Pt are electrodes that help transfer the electrons but not directly participate in the reaction. It is given by the table as they stay neutral the entire reaction.

Norman Dis4C

Should it be lnK or lnQ when it reaches equilibrium or the two have the same value.

Norman Dis4C

In this question, E is given and F is a constant. The only thing you need to find is n, which is the electron transferred. By breaking down the reaction into two half-reaction, you will know the number of electrons transferred by the change in its charges.

Norman Dis4C

Honestly, it would not matter. If your E is negative, you simply reverse it and the position of reactants and products.

Norman Dis4C

Be aware that since an equation is composed of two half reaction. You only need to know the moles of electron transferred in one group but not adding up that of both reactions.

Norman Dis4C

Will Ecell stays the same as the reactions go on or the value goes to 0 as it becomes equilibrium?

Norman Dis4C

Since K means the equlibirum ration of product over reactant. We use the equation to calculate K.

Norman Dis4C

You use both these equations
∆G° = - RT ln K
∆G° = ∆H° - T∆S°
and derive the van't hoff equation form balancing both side.

Norman Dis4C

It is used to calculate K when delta H and S are known.

Norman Dis4C

Can someone explain to me why we use Delta H naught and S naught for Van't Hoff Equation even though there is a temperature change? Doesn't naught mean standard condition? Thanks in advance,

Norman Dis4C

On the lecture slides, it says both delta H and delta S are constants.

Norman Dis4C

It would be easier if you draw out the graph and compare the value of it. The graph is shown in 4J.4 in the textbook.

Norman Dis4C

It will decompose but not all reaction is rapid, the rapid ones are called labile.

Norman Dis4C

Are you sure that is what Dr. Levelle said? To my understanding, you can still calculate for G using deltaG=-Tdelta Stotal, which left out enthalpy but not entropy.

Norman Dis4C

The state of the substance is determined by its most stable phase. For carbon, it is solid

Norman Dis4C

Can someone explain the idea of the equation U=3/2 nRT and how it is used?

Norman Dis4C

For an isolated system will all values of deltaU=q+w equal 0 or is it just the deltaU that is 0?

Norman Dis4C

but why is the answer not 490J but 9000J?

Norman Dis4C

Can someone explain why the volume of a closed system can change? Any examples would help!

Norman Dis4C

Mine says 8 as well, but it is not the latest edition, so 28 should be the right answer.

Norman Dis4C

For this type of question, do we assume the condition is constant pressure or is there any hint in the question?

Norman Dis4C

Yes, because steam contains more heat that is absorbed during the phase change. So it releases the heat when condensing on our skin.

Norman Dis4C

Yes, the opposite of these process is condensation, freezing, and deposition respectively, which are all exothermic.

Norman Dis4C

Since it is the most stable form of an element being turned into the most stable form, it is essentially the same substance on both sides of the reaction. The energy change is therefore 0.

Norman Dis4C

Heat is just like work, it is pathway-dependent, so you must take into account how much heat goes in and out of the system. Enthalpy, on the other hand only accounts for the initial and final stage of the reaction.

Norman Dis4C

It's both 1 atm for gas and solution, but solution has to be 1M as well.

Norman Dis4C

How is K different from Kc? In the textbook, it listed out both K and Kc values and I'm wondering which one I should use for calculation.

Norman Dis4C

Since being protonated is accepting H+, we know that it will appear on the right side of the equation as being the protonated product of the reactant.

Norman Dis4C

You could use these two interchangeably since Ka * Kb = Kw, it's just a matter of conversion and what you're looking for.

Norman Dis4C

For the second question where you mention determining whether it's acid or base by looking at pH<pKa and pH>pKa or pKb, is that mentioned in class? I don't remember Lavelle saying that.

Norman Dis4C

You can only determine the pH with the acid and base concentration. determining whether the acid is strong or weak, you have to analyze its formula or even draw out its structure.

Norman Dis4C

Total pressure is the sum of all gas's partial pressure. Since we only have to solve for the gas used in the reaction, we use the partial pressure instead.

Norman Dis4C

Thanks! These notes are really helpful! I wonder if we have access to Lavelle's slides by any means.

Norman Dis4C

The equilibrium constants do not change as long as the temperature stays the same.

Norman Dis4C

Pressure changes that cause volume change can also affect where the equilibrium sits since the concentration is different.

Norman Dis4C

The reaction sits to the right when Q<K since there are more reactants than the products. To achieve an equilibrium state, more products are formed.

Norman Dis4C

you could also measure the formal charge of the site with lone pairs.

Norman Dis4C

Chelating is basically any polydentate ligand, and denticity is number of bonding sites.

Norman Dis4C

for polydentate, you have to add those prefix in front of the ligands.

Norman Dis4C

NO2 + H2O --> H2NO3, SO3 + H2O --> H2SO4

Norman Dis4C

I recommend you read this
https://chem.libretexts.org/Courses/Mou ... _and_Bases

Norman Dis4C

Are transition metal cations acidic since they accept electrons from ligands?

Norman Dis4C

Can someone define acid and base? Is the compound only considered acid and base when dissolved? For example, is SO4 acidic since it forms H2SO4 in the water?

Norman Dis4C

Are we supposed to memorize the names of the ligands or the general rule naming rules of the coordinate compound instead?

Norman Dis4C

The atom that is linked to the metal atom is often written first to emphasize the bonding sites. You could also underline the bonding atom to indicate.

Norman Dis4C

Smaller cations should have more polarizability because it exerts a stronger attraction force to nearby electrons.

Norman Dis4C

Since each myoglobin binds to one O2. 4 myoglobin, which is hemoglobin, should bind to 4 O2.

Norman Dis4C

I think the term Lewis acid or base only describes the atom or molecule that gives or receives the electrons. So even metal cations are considered lewis acid.

Norman Dis4C

The ability to form coordinate covalent bonds allows the molecule to form a complex structure, thus the shape of the compound makes it biologically significant.

Norman Dis4C

Can someone explain to me why tetradentate is less common than the others?

Norman Dis4C

Both size and electronegativity affect the result, but since the size of atom follows the same trend as that of electronegativity, PF should have longer bonds.

Norman Dis4C

For both molecules, the electronegative force cancels out, but since AsF5 has more electrons, it has a higher boiling point.

Norman Dis4C

Polarizing power is the tendency of ions to cause large distortion, cations that are small have higher polarizing power, and anions that are larger are more "polarizable". Polarizability follows the trend of electronegativity and it applies to covalent compounds.

Norman Dis4C

Can someone explain to me why double bond is just slightly stronger than single bond? Why does not the strength between the two atoms double?

Norman Dis4C

A covalent bond is stronger than ionic bond because ionic bonds dissolve in water

Norman Dis4C

The number of bonds have nothing to do with electronegativity. Electronegativity is defined as the tendency to attract electrons in a covalent compound.

Norman Dis4C

Increasing sizes or molar mass results in stronger attractive interactions. Stronger attractive interactions have lower interaction potential energy since the equation of interaction potential energy has a negative sign.

Norman Dis4C

For covalent compounds, it really depends on how polarized the substance is. Polar covalent compounds also dissolve in water.

Norman Dis4C

All you need to know is the relationship between the different variables. There is no calculation on the test.

Norman Dis4C

Can someone explain the equation -(alpha1 alpha2)/(r^6) to me? What does the negative sign have to do with attraction force?

Norman Dis4C

Molecules with electronegativity difference >1.5 but <2 are considered ionic or covalent?

Norman Dis4C

Dispersion, induced dipole induced dipole, London, and Van der waals all mean the same thing.

Norman Dis4C

atoms with the lowest ionization go in the middle with the exception of H. H is never central!

Norman Dis4C

Can somebody explain to me why the additional electron added to phosphorous goes into the 3d orbitals instead of 4s? Doesn't 4s orbital have lower energy until both 3d and 4s are occupied?

Norman Dis4C

Hey, can somebody explain how resonance structure look like visually? How can an electron be divided or separated into different multiple bonds or is resonance structure just conceptually viable?

Norman Dis4C

I think the term valence electron is the # of electrons in the outermost shell (at the molecule's ground state). So it should be less than 8.

Norman Dis4C

I think delocalized electrons occur not because of similar electronegativity but a molecule having more than one acceptable lewis structures.

Norman Dis4C

Any atoms that have orbitals higher than 3S can break the octet rule.

Norman Dis4C

Can someone explain the difference between these two terms?

Norman Dis4C

Can someone explain this sentence to me: Electrons in an s-orbital are more effective than those in other orbitals at shielding other electrons from the nuclear charge because an electron in an s-orbital can penetrate to the nucleus of an atom. What does it mean to penetrate to the nucleus of an atom?

Norman Dis4C

Convert anything to meter first before you convert it to another unit. For example, one nanometer is 10^-9 meter, which is 10 Angstrom.

Norman Dis4C

The answer is the Photoelectric effect. Since one photon interacts with one electron, the only way to knock off the electrons from the metal is to increase the frequency, which subsequently increases the energy per photon. If photon behaves like waves, then you should be able to increase the intensi...

Norman Dis4C

Can we also find the frequency of the object using the DeBrogile Equation after we find the wavelength?

Norman Dis4C

What does the term "hidden variable" mean in the context of Copenhagen interpretation and how is it different from Heisenberg Indeterminacy equation?

Norman Dis4C

I got tricked by the unit as well... There is one question on the textbook that requires you to convert Kev to Joule before calculation.

Norman Dis4C

17. In an atomic absorption spectrum what does one line (one wavelength) represent? A. It represents the wavelength of light emitted by the gas sample. B. It represents the wavelength of light absorbed by the gas sample. C. It represents the frequency of light emitted by the gas sample. D. None of t...

Norman Dis4C

Atoms only absorb and release lights with a specific wavelength. The frequency of the light determines how much energy the photons have, so it only emits energy when the light's energy matches ΔE between energy levels. Therefore, light is not continuous and we can only see groups of spectral lines o...

Norman Dis4C

Increasing the amplitude or intensity of a wave increases the energy that bounces back, but , for light, it doesn't. Instead, you have to increase the frequency of the light. From the equation E=hv, we derived that whenever frequency(v) increases, the energy of the photon(E) also increases.

Norman Dis4C

I think it has to do with hydrogen having only one electron making it one of the easiest to observe. For molecules, orbits will overlap with each other, creating hybrid orbitals. This makes molecules much harder to observe since you're now dealing with new orbitals created by two or more atoms.

Norman Dis4C

Why does the gap between different shells decrease as the level goes up?

Norman Dis4C

"Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this question, suppose that you prepare a solution of a supposedly active substance, X, with a molarity of 0.10 mol/L. T...

Norman Dis4C

First, you balance the equation and find out the ratio. Then, you compare the ratio you get from the equation to the mole ratio you actually have. Start from here, it becomes obvious.

Norman Dis4C

A cation is positive. Electron is negatively charged. So it loses electrons.

Norman Dis4C

Start with the element that appears the least number of times on both sides. If more than one compound from the same side of the equation have the elements, it would be harder to balance because there will be two coefficient.

Norman Dis4C

You only have to imagine there is 100 grams when %composistion is given but not the mass. (the number of grams you used is not fixed, you can use whatever you want as long as you keep the calculation simple and clear, but usually, 100 grams is the most straightforward and simple)

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