CHEMISTRY COMMUNITY

Jonathan Zhao 4H

Most of the time, you will have to find the order of the reaction by testing the different graphs given in lecture and seeing which one is linear.

Jonathan Zhao 4H

If you look at the class website, you can find videos and links that will help with the math/calculus portion of this topic.

Jonathan Zhao 4H

Whether or not the rate law depends on the concentration of reactants depends on the order to the reaction.

Jonathan Zhao 4H

Yes, for my version, increasing the temperature led to a basic solution.

Jonathan Zhao 4H

Yes, correct. The more positive the E value, the stronger the oxidizing power.

Jonathan Zhao 4H

For the pH question, I think you had to use the Van't Hoff equation, which was given on the equation sheet. This equation relates the change in the equilibrium constant with the change in temperature. Using this equation, you can find the new equilibrium constant as a result of the change in tempera...

Jonathan Zhao 4H

In my opinion, just know the common ones, such as group 1 metals and group 2 metals, which are +1 and +2, respectively. Also, know that oxygen is generally -2 and chlorine is generally -1. Not sure if we will need to memorize the others.

Jonathan Zhao 4H

A reaction is considered spontaneous if the Gibbs free energy is negative. Knowing only the change in enthalpy or entropy cannot determine spontaneity.

Jonathan Zhao 4H

A salt bridge maintains the electrical neutrality of a battery. Negative ions would flow into the left compartment while positive ions would flow into the right compartment.

Jonathan Zhao 4H

Yes, essentially the third law of thermodynamics is saying that at 0 degrees K, there is no vibrational, rotational, or translational entropy. The only possible entropy results from positional and residual. Thus, knowing the Boltzmann equation would come in handy when asked a question about the resi...

Jonathan Zhao 4H

Yes, the system vs. surrounding should not be something you have to memorize. As mentioned before, the system is simply the situation in question, such as a piston. Since the first law of thermodynamics states the conservation of energy, a change in energy of the system means a resultant change in s...

Jonathan Zhao 4H

I believe you mean for Test 2?

Jonathan Zhao 4H

Enthalpy has the letter "h" in it, so it corresponds to H. Not sure if that helps much, but usually, you should be able to differentiate between entropy and enthalpy based on what the problem is asking.

Jonathan Zhao 4H

Since he said up to entropy, it is up to the "Second and Third Laws of Thermodynamics", but only part of Chapter 9.

Jonathan Zhao 4H

Yes, you can check "Important Midterm Information" on his website.

Jonathan Zhao 4H

Yes, use the conversion ratio which should be given to us, either in the problem or on the formula sheet to convert.

Jonathan Zhao 4H

This equation describes an ideal gas, which is essentially a simplified model of real gases to help us in calculations. Since there are 4 unknown's in this equation, we can use this equation when we have three givens, which then can be used to calculate the final unknown.

Jonathan Zhao 4H

Yes, we should still be able to do thermochemistry problems for HW.

Jonathan Zhao 4H

The standard enthalpy of formation is the net change in enthalpy, or in simpler terms, the net change in heat, for one mole of a substance in standard state to be formed from its pure elements. A standard enthalpy of formation of 0 means that the substance is already in standard state.

Jonathan Zhao 4H

Essentially, the change in internal energy of a system, deltaU, equals the net heat transfer into the system, Q, plus the net work, W, done on the system. This is the first law of thermodynamics.

Jonathan Zhao 4H

Carbon and Hydrogen cannot have a triple bond because a hydrogen atom only has one valence electron.

Jonathan Zhao 4H

A small Ka essentially means a large Kb, since they are inversely proportional. The larger the acid or base equilibrium constant, the stronger the acid or base.

Jonathan Zhao 4H

Protonation and Deprotonation is simply the acceptance/donation of a proton as a result of a reaction. For weak acids/bases, since it is not complete disassociation, there is a percentage that remains an acid/base as a result of equilibrium. Percent protonation is the change in concentration for the...

Jonathan Zhao 4H

Usually, if the problem gives you initial concentrations of the reactants and asks for the equilibrium concentrations of each molecule, you can most likely use an ICE table to solve the problem.

Jonathan Zhao 4H

No, you do not need to include solids and liquids when calculating the equilibrium constant.

Jonathan Zhao 4H

Yes, you could easily convert between partial pressure to concentration by using PV=nRT.

Jonathan Zhao 4H

Yes, it is also equivalent to 100 kPa, if that helps.

Jonathan Zhao 4H

Yes. For instance, oxygen is often displayed without its lone pairs, so we must account for them when determining hybridization.

Jonathan Zhao 4H

Although S has a higher electronegativity leading to stronger dipole-dipole interactions, Se has a larger atomic mass, resulting in stronger London dispersion forces which are more stronger than the dipole-dipole interactions. Thus, H2Se has a higher boiling point.

Jonathan Zhao 4H

The electron density shape would be based off the trigonal bipyramidal shape. The three lone pairs will take the three equatorial positions, leaving the two axial positions for the atoms. This would result in a symmetrical linear molecular shape.

Jonathan Zhao 4H

Higher electronegativity allows for easier dissociation. A strong acid completely dissociates in water, so the higher the electronegativity, the stronger the acid.

Jonathan Zhao 4H

Yes, a Bronsted acid donates a hydrogen ion (H+).

Jonathan Zhao 4H

I believe it is asking for the lewis structure with the greatest contribution to the resonance, so essentially the most stable structure.

Jonathan Zhao 4H

To my knowledge, not all compounds containing period 3 or below elements are hypervalent compounds as the expanded octet is not always necessary.

Jonathan Zhao 4H

Essentially, an equatorial lone pair is generally the lowest energy because it is only strongly interacting with the two axial electron pairs, whereas axial lone pair strongly interacts the three equatorial electron pairs.

Jonathan Zhao 4H

Nitrogen would be the central atom in this case. If the chemical formula was given as OCN-, then carbon would be the central atom.

Jonathan Zhao 4H

For instance, the electron density geometry for H2O is tetrahedral, since there are 2 bonded pairs and 2 lone pairs. The molecular geometry of H2O is bent, since only 2 atoms are bonded with the central atom.

Jonathan Zhao 4H

I'm not exactly sure about ClO2+, but generally, you would want the formal charge for the central atom to be 0, and the outer atoms with the charge.

Jonathan Zhao 4H

Lone pairs are considered as an electron density when regarding shape of a molecule. It has a larger repulsion when compared to bonded pairs of electrons.

Jonathan Zhao 4H

Water is a dipole as the oxygen is electronegative, causing O to be more negative than the H's. If a water molecule (dipole) was nearby a N2 molecule (nonpolar), the N closest to the O would have a slightly positive charge, causing the other N to have a slightly negative charge, creating a dipole. T...

Jonathan Zhao 4H

Essentially, the larger the atom (the more electrons), the easier it is for electrons to become distorted, since the pull on the outer electrons is less for larger atoms.

Jonathan Zhao 4H

The electronegativity of oxygen causes water to be polar, leading to hydrogen bonding. Because of hydrogen bonding, H2O requires more energy needed to break the bonds, thus it has a much higher boiling point/melting point than that of H2S.

Jonathan Zhao 4H

You would have to find the formal charges of each atom in each structure. You would want to find the structure with the least formal charge (lowest energy).

Jonathan Zhao 4H

Hund's rule states that every subshell must be singlely occupied by one electron before it can be doubly occupied. For instance, you know the electron config of Ga, which is [Ar]3d10 4s2 4p1. There is one unpaired electron in this case, because there is one electron in the 4p orbital. For Se, the el...

Jonathan Zhao 4H

I think just to be safe, you should follow the sigfig guidelines.

Jonathan Zhao 4H

To my knowledge, it does not matter which side you put the dots, as long as you follow Hund's rule where electrons fill the available subshells before pairing up to have the lowest energy state.

Jonathan Zhao 4H

Yes, definitely use meters per second. And in this case, using the KE = (1/2)mv^2 then using the E = (planck's constant)(frequency) would be easiest to solve this problem.

Jonathan Zhao 4H

The uncertainty in momentum is inversely proportional to the uncertainty in wavelength, meaning a larger uncertainty in momentum will lead to a smaller uncertainty in wavelength, and vice versa.

Jonathan Zhao 4H

I'm not quite sure of the difference between atomic absorption vs. atomic emission spectroscopy, but I do know that the lines on the spectrum represent the different energy levels that the electron can be on.

Jonathan Zhao 4H

I believe just the drawing of the box is sufficient. But, you could include the wavelength of the electron if you want to.

Jonathan Zhao 4H

I believe we discussed Coulomb's law mainly to demonstrate the effects of shielding on electrostatic attraction.

Jonathan Zhao 4H

Using nanometers would be better for wavelength.

Jonathan Zhao 4H

For me, it helps to draw the diagram that Lavelle draws in the lectures. This helps me visualize the electron going from its "excited" state to "resting" state and also the change in energy, which results in the release of photons.

Jonathan Zhao 4H

Technically, all matter has wave-like properties, but they can only be noticed in moving objects with small mass.

Jonathan Zhao 4H

Is there a list of all the common ions that we should know? I know a few but I'm not sure if there are more that I am missing.

Jonathan Zhao 4H

To determine maximum production, you need to know the number of moles of each reactant. The number of moles of the limiting reactant should determine maximum product via the molar ratio given. In this example, you would need more information in order to solve this question.

Jonathan Zhao 4H

Start by finding the number of moles of each reactant that you have. To do that, you need the molar mass, which can be found using the periodic table. After knowing how many moles of each reactant you have, compare these numbers to the molar ratio given in the equation to find out which particular m...

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