CHEMISTRY COMMUNITY

Eunice Lee 1A

Yes, any molecules in the gas phase would be affected.

Eunice Lee 1A

How is ln[R]=-kt+ln[R]0 useful? What does it tell us?

Eunice Lee 1A

I don't really understand what a zero order reaction is. Can someone explain what it is and give an example of one?

Eunice Lee 1A

What is a pseudo-first-order reaction and how do you get one from a second-order reaction?

Eunice Lee 1A

Can someone explain to me why and how to solve 7A.1 from the 7th edition textbook? I looked at the solutions manual but I didn't understand where these formulas and units came from.

Eunice Lee 1A

Does anyone know how to tell which order a reaction is, and what are the differences between the different orders?

Eunice Lee 1A

A greater enthalpy can cause greater entropy.

Eunice Lee 1A

During a discussion session, our TA listed the order that substances in different phases should be written in a cell diagram. Does anyone know the order? (I think it was solids on the outer sides and aqueous on the inner sides of the cell diagram, but I'm not sure.) For reference: I think it was som...

Eunice Lee 1A

For an acidic solution, balance oxygen with water molecules and balance hydrogen with H+. For a basic solution, balance oxygen with water molecules, and balance the hydrogen from those water molecules with water molecules on the other side of the equation. Then, balance oxygen with OH- on the first ...

Eunice Lee 1A

What's the difference between an electrochemical cell and an electrolytic cell?

Eunice Lee 1A

When writing out a cell diagram, is there a specific order the ions should be listed in?

Eunice Lee 1A

Can someone explain what the Daniell cell mentioned in the book is?

Eunice Lee 1A

You can figure out the spontaneity of a reaction simply from whether or not delta G is positive or negative.

Eunice Lee 1A

The book mentions the Clausius inequality, which states that deltaS is greater than or equal to q/T for a reversible process, but then why is there another equation that states that deltaS is only equal to q/T?

Eunice Lee 1A

So I know that you can derive deltaS=nRln(P2/P1) from deltaS=nRln(V2/V1) due to Boyle's law, but how do you get deltaS=Cln(T2/T1)? Where does the C come from?

Eunice Lee 1A

q represents the heat supplied to a system. Delta H represents the change in enthalpy, which is the change in energy as expansion work during heat transfer. When the pressure is constant, the heat supplied to a system is equal to the change in energy, so delta H and q are equal.

Eunice Lee 1A

When do you use w = -Pex(deltaV) vs. w = -nRTln(V2/V1)?

Eunice Lee 1A

Can someone give an example of each of the types of thermodynamic systems? (For example, in discussion, we talked about how a closed thermos is an example of an isolated system)

Eunice Lee 1A

In class, Professor Lavelle talked about how we would only need to know the enthalpies of the bonds involved in the reaction, not the other bonds in the molecules uninvolved in the reaction itself. How do we know which bonds are involved in the reaction? Would we just have to draw the Lewis structur...

Eunice Lee 1A

What's the difference between delta U and delta H? The textbook states that heat transfer at constant volume is delta U and that heat transfer at constant pressure is delta H, but can someone give more detail as to why that is?

Eunice Lee 1A

Do we have to know the equipartition theorem? We haven't gone over it in class, but it's on the syllabus.

Eunice Lee 1A

You would need the enthalpy of each bond in the reaction broken and each bond in the reaction formed. Add these values together to get the total change in enthalpy.

Eunice Lee 1A

Volume would also need to be constant, as pressure and volume are dependent on each other.

Eunice Lee 1A

Since reversing the equation would reverse the chemical process taking place, the sign of the enthalpy would change. For example, if you start with an exothermic reaction, the enthalpy would be negative because the reactants are releasing/losing heat to form the products. If you reverse this reactio...

Eunice Lee 1A

Water isn't included because it's usually the solvent for the equation.

Eunice Lee 1A

For exothermic/endothermic reactions, in which directions do the reactions shift when temperature is changed, and why?

Eunice Lee 1A

The conjugate seesaw states that the stronger the acid, the weaker its conjugate base. The stronger the base, the weaker its conjugate acid.

Eunice Lee 1A

The value of Kc is always constant for a given reaction at a constant temperature. A change in concentration of the reactants or the products will just shift the direction of the reaction.

Eunice Lee 1A

A homogeneous reaction is a reaction with reactants and products that are all in the same phase. In contrast, heterogeneous reactions are reactions with two or more different phases.

Eunice Lee 1A

I know that solids and liquids are not included when considering the equilibrium constant, but are they also not included when calculating the reaction quotient?

Eunice Lee 1A

Protons that are attached farther away on the molecule from the central atom/ion are more likely to be given.

Eunice Lee 1A

When using an equilibrium table to calculate the pH of a salt solution, can we use it for any type of reaction?

Eunice Lee 1A

The conjugate base of an acid would be the product of that acid losing a proton (H+). The conjugate acid of a base would be the product of that base gaining a proton (H+).

Eunice Lee 1A

In addition, say we replace the lone pairs in AX4E2 with bonded atoms, making it AX6. This molecule is square bipyramidal, which has 90-degree bond angles all around. The atoms replaced with the lone pairs aren't necessarily the axial atoms because the molecule is symmetrical in all directions.

Eunice Lee 1A

The axial bonds have a 90-degree bond angle with the equatorial bonds, while the equatorial bonds have a 120-degree bond angle with each other. Since the bond angles of the equatorial bonds are greater than those of the axial bonds, these atoms are replaced with the lone pairs because it gives the l...

Eunice Lee 1A

Lone pairs repulse bonds even more than other bonds do because they belong to the respective atom alone instead of being shared. Because of this, they push on the existing bonds more, resulting in an even more distorted shape. They are not considered when identifying the shape, but they contribute t...

Eunice Lee 1A

Lone pairs affect bond angles and molecular shape since they also have a charge. However, the molecular shape has to do with the shape of the actual molecule, not the electrons, so they are not accounted for in that sense.

Eunice Lee 1A

I've been reading everywhere, and I don't think I really understand what pi and sigma bonds are and what the difference between them is. Can someone please explain?

Eunice Lee 1A

Can someone list some octet exceptions and explain why they're exceptions (if there are reasons)?

Eunice Lee 1A

Though the bonds themselves are what you should consider in terms of what to call the shape of the molecule, lone pairs should also be taken into account as they can change the measurement of the angles in between bonds.

Eunice Lee 1A

The more bonds that are shared in between two atoms, the shorter the bond between them will be. Multiple bonds cause the atoms to have stronger pulls on each other and bring them closer. Therefore, more bonds = less distance.

Eunice Lee 1A

Having zero as the formal charge on an atom is more important, as some elements don't completely follow the octet rule and can have more than eight valence electrons.

Eunice Lee 1A

How do resonance structures affect bond length?

Eunice Lee 1A

The overall charge can be zero, but it doesn't have to be.

Eunice Lee 1A

You can use a double bond to change the formal charge on an atom (if it's not zero/stable) or if there are not enough electrons in the molecule.

Eunice Lee 1A

As stated above, there were four different events listed: reading, getting a dental x-ray, making popcorn in a microwave oven, and acquiring a suntan. Keep in mind that these all have different wavelengths.

Eunice Lee 1A

If the momentum is not provided, you can calculate it with p = mv, where m is mass and v is velocity. Since h is in terms of J, don't forget to convert mass to kg and velocity to m/s!

Eunice Lee 1A

The Einstein equation can only be used for photons, while the De Broglie equation can be used for anything.

Eunice Lee 1A

Often times, the amount can vary depending on the transition metal. Usually, it's just a matter of memorizing which ones tend to lose how many electrons.

Eunice Lee 1A

Atoms of different elements still have their respective number of protons in the nucleus. Properties of elements depend on their nucleus. Electrons mainly affect bonding.

Eunice Lee 1A

In addition to the previous response, the principle quantum number is usually determined by the period the atom is in in the periodic table. For example, an atom ending in 3p will have the principle quantum number 3.

Eunice Lee 1A

A black body is a material that can hypothetically absorb all light frequencies.

Eunice Lee 1A

Light intensity is proportional to the number of protons. The more intense a light is, the more photons it has.

Eunice Lee 1A

Light acts as a particle because it releases in streams of photons, and it acts as a wave because it can be intensified.

Eunice Lee 1A

Can someone explain the importance of the atomic spectrum and what we use it for?

Eunice Lee 1A

Can someone explain what the threshold energy in the photoelectric experiment is?

Eunice Lee 1A

When calculating wavelength, does it matter what the unit is? For example, the speed of light is measured in meters per second, but some wavelengths are given in terms of nanometers. Should I convert it to meters first, plug it into an equation, then re-convert it back afterwards, or does it not mat...

Eunice Lee 1A

For question F9 (7th edition), the question asks for the ratio of C:H:O, given certain mass percentages. Should we answer in the form of an empirical formula, or in the form of an actual ratio (#:#:#)?

Eunice Lee 1A

Avogadro's number isn't just limited to just atoms or molecules, but you can even describe 6.0221 x 10^23 cups as a mole of cups. Avogadro's number can be used for anything!

Eunice Lee 1A

The diatomic molecules are hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. Most of these are located in the upper right corner of the periodic table. You can also think of it as the halogens + HNO!

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