CHEMISTRY COMMUNITY

Nicholas Le 4H

A catalyst can be found in the beginning of the reaction, while an intermediate is found in the later steps.

Nicholas Le 4H

The units for k change depending on the order so that it can produce the correct units for the rate which is always in molarity per second.

Nicholas Le 4H

The rate constants are different from the actual rate of the forward and reverse reaction. Also, the rate constant does not necessarily correspond to the rate of the reaction as it also depends on the concentrations and the order of the species.

Nicholas Le 4H

What exactly is a half-life? I do not understand the concept behind this.

Nicholas Le 4H

Microscopic reversibility basically says that the reaction has the same path for both the forward and reverse directions.

Nicholas Le 4H

Yes, it is applicable to all first order rate reactions.

Nicholas Le 4H

You can find help in the class resources section. Also, you just need to understand the concepts behind it and how to use the final equations that are produced by calculus.

Nicholas Le 4H

When do we use platinum metal in the cell diagram, and why do we use platinum as the metal?

Nicholas Le 4H

You must balance the elements other than oxygen and hydrogen first. Thus, you can do both.

Nicholas Le 4H

Yes, n is the number of moles of electrons transferred and can be found through the oxidation or reduction half reactions.

Nicholas Le 4H

A positive cell potential means that the reaction is spontaneous, while a negative cell potential means that the reaction is not spontaneous.

Nicholas Le 4H

The cathode is the reduction half reaction, while the anode is the oxidation half reaction. Basically, whichever chemical species being reduced will be the cathode and whichever chemical species being oxidized will be the anode.

Nicholas Le 4H

A galvanic cell and voltaic cell are essentially the same and are interchangeable.

Nicholas Le 4H

Yes, you raise it to the number of Avogadro's constant if they ask you to use one mole of a substance.

Nicholas Le 4H

You use the value for Cv when the volume in the problem is constant, and you use the value for Cp when the pressure in the problem is constant.

Nicholas Le 4H

Yes, you can use this when pressure is constant since the change in enthalpy is equal to q when pressure is constant.

Nicholas Le 4H

Closed systems can have constant or changing pressure or volumes.

Nicholas Le 4H

The first equation would only be used for questions that deal with reversible expansion, while the second equation of w=-PdeltaV would only be used for irreversible expansion.

Nicholas Le 4H

Delta U would be 0 due to the fact that it is an isolated system. Since it is isolated, the internal energy will remain the same.

Nicholas Le 4H

Yes, the change in internal energy of an isolated system is 0.

Nicholas Le 4H

Most likely not as we will be expected to already know how to draw Lewis structures from chem 14A.

Nicholas Le 4H

A closed system can only exchange energy with its surroundings, while the isolated system cannot exchange anything with its surroundings.

Nicholas Le 4H

When referring to surroundings in chemistry, we usually mean everything outside the system that we are looking at. This means there really is not a boundary that exists for how far the surroundings can go.

Nicholas Le 4H

Why does the temperature not change during a phase change even though more heat energy is being added?

Nicholas Le 4H

Heat capacity is the amount of heat needed to increase the temperature of one gram of a substance by one degree. It has a state property because it is independent of how the substance was prepared.

Nicholas Le 4H

Steam causes a more severe burn than that of boiling water even when they are at the same temperature due to the fact that steam holds more heat energy as becoming a vapor from a liquid requires a large amount of heat before it can change phases.

Nicholas Le 4H

Sitting to the left just means that the reactants are being favored over the products. Thus, if it is shifting left, the reactants are being favored to reach equilibrium.

Nicholas Le 4H

Why does the equilibrium constant change when the temperature changes?

Nicholas Le 4H

We leave out solids and liquids because they do not affect the equilibrium. We only account for species in the aqueous and gas phases when calculating equilibrium.

Nicholas Le 4H

If an expression for an ice table becomes cubic and is no longer quadratic, how exactly would we solve for the x value to find the concentrations of the species?

Nicholas Le 4H

You can calculate the C expression by combining the initial and change together. Then to find the value of the variable x in the C expression, you set all the expressions in the C category into the equilibrium constant form where products is over reactants and set it equal to the equilibrium constan...

Nicholas Le 4H

Both Kc and Kp are both equilibrium constants except that Kc is for molar concentrations while Kp is for partial pressures.

Nicholas Le 4H

Why is HBr a stronger acid than HF?

Nicholas Le 4H

Yes, in most cases in which we work with NH3, it is considered in the terms of bronsted base.

Nicholas Le 4H

You would draw the lewis structure in terms of ionic compounds as it is not covalent, so thus you would draw K with a plus charge next to OH with a negative charge while showing the paired shared and lone electrons on and between the O and H. KOH is considered a strong lewis base and is usually not ...

Nicholas Le 4H

HCl is a strong acid as the most of the halogens in group 7 except flourine form strong acids due to the fact that they pull the electron density from hydrogen, and as it goes down the group the bond gets weaker and thus increases the strength of the acidity.

Nicholas Le 4H

NaOH is a strong base because any hydroxides bonded to group 1 elements are considered strong bases.

Nicholas Le 4H

It should be written as OH2 when you want to demonstrate that the oxygen is bonding to the central transition metal.

Nicholas Le 4H

Can someone explain to me the difference between Lewis(acids and bases) and Bronsted(acids and bases)?

Nicholas Le 4H

You should write it without spaces just to be safe and yes you add an O to anionic ligands.

Nicholas Le 4H

You calculate the oxidation state of the transition metal by first finding the overall charge of the ligands attached to it. After you have found that, you will want to look at the overall charge of the whole compound. You should then be able to find the oxidation state of the transition metal as it...

Nicholas Le 4H

How come hybridization does not occur when forming pi bonds, but it does occur when forming sigma bonds?

Nicholas Le 4H

Yes, double bonds consist of one sigma bond and one pi bond.

Nicholas Le 4H

Yes, sigma bonds are longer than pi bonds since pi bonds have a larger electron density and thus have greater attraction between the electrons and the nucleus's protons. Thus, pi bonds are shorter than sigma bonds.

Nicholas Le 4H

The test will be on everything after the midterm to now. Essentially, you must understand the last concepts in chemical bonding, intermolecular forces, and both VSEPR and valence bond theory.

Nicholas Le 4H

Do we need to understand how to draw the molecular shape in which it shows how the atoms are in different dimensions using techniques, such as dotted lines?

Nicholas Le 4H

Yes, they are just considered one electron density.

Nicholas Le 4H

As the s-character of a hybrid orbital increases, the bond angle increases.

Nicholas Le 4H

Yes, you are correct the angle is actually less than 90 degrees due to the electron repulsion from the electron lone pair.

Nicholas Le 4H

How exactly does a dipole induce another dipole onto a neutral atom if the neutral atom only has London dispersion forces?

Nicholas Le 4H

Since they actually exist as a hybridization resonance structure, the true bond lengths exist between 120 and 140. We need further experimental data to get a more accurate answer of the true bond length.

Nicholas Le 4H

A larger bond results in a weaker bond due to the fact that there is more distance the bond is covering. Using coulomb's law, F=(K(q1*q2))/r^2, as distance, r, increases, the force becomes weaker as it is inversely proportional to force.

Nicholas Le 4H

Dispersion forces increased as we go down the periodic table due to increased electrons which lead to more London dispersion forces as there is more temporary interactions between electrons. As these forces increased, atoms are held more tightly together, which leads to states, such as liquids and s...

Nicholas Le 4H

Is the central atom in the Lewis structures based off of which atom has the lowest electronegativity or which atom has the lowest ionization energy?

Nicholas Le 4H

Yes, the oxygen carries the formal charge due to the fact that it is the most electronegative. Also, because bromine can only have one shared bond pair, which forces oxygen to hold the negative charge.

Nicholas Le 4H

A shortcut you can use when dealing with larger molecules, such as CH3NH2, is that you split up the molecule by the different compounds within it. In this case, you place the carbon with the three hydrogen atoms and the nitrogen with the 2 hydrogen atoms as there are two separate compounds within it...

Nicholas Le 4H

Hydrogen atoms can only form one bond known as a duet as it cannot form an octet. In covalent bonding, a central atom must have enough available electrons to form at least two bonds.

Nicholas Le 4H

Why does the second ionization energy of the alkali metals increase so dramatically after the first ionization energy?

Nicholas Le 4H

An element like Argon is used as it is the closest noble gas that can be used for writing short-hand ground state electron configurations based off of noble gases.

Nicholas Le 4H

Valence electrons can be determined by looking at their group number at the top. For, example chlorine is in group 7, so thus it has 7 electrons. In cases of ions like Ag+, one should write out the ground state electron configuration to figure out the valance electrons as they differ from the regula...

Nicholas Le 4H

Removing the second electron from an atom is more difficult due to the higher ionization energy required to remove it. This is due to the fact that the nuclear charge has a stronger pull on the remaining electrons as there is now one less electron. Thus, with a stronger attraction due to a positive ...

Nicholas Le 4H

The atomic radius would not increase across a period due to the fact that the quantum number stays the same and that there are now more protons, which essentially produces a larger effective nuclear charge on the electrons.

Nicholas Le 4H

To what extent of the Shrodinger Equation will we have to understand for the upcoming test on quantum? Do we just need to understand the concepts behind it or must we understand how to calculate solutions using the equation as well?

Nicholas Le 4H

Adding on, you can use the formula E=hR(1/n^2(final)-1/n^2(initial)) to find the energy difference in one step. Then plugging it back into the equation E=hv to find frequency and then using C=wavelength(frequency) to find wavelength.

Nicholas Le 4H

A nodal plane is a plane in space where the electron probability reaches zero. Usually, there exists nodal planes at the nucleus. The s subshell is the only subshell that is symmetrical and thus does not have a nodal plane.

Nicholas Le 4H

The solutions manual suggests that A=Na B=Cl C=Na ion and D=Cl ion based off the diagram given, but chlorine should have a smaller atomic radius than that of sodium at ground state. So is this a typo and if not can someone explain to me how they got that answer?

Nicholas Le 4H

Is there any element that actually incorporates g and h orbitals and is it even under the scope of our class that we must learn this?

Nicholas Le 4H

C is a constant value for the speed of light which is 3.00X10^8 meters/second.

Nicholas Le 4H

Most likely there is not a maximum for the length of a wavelength. We most likely will not have to deal with this as it is probably outside the scope of which this class teaches as it was not mentioned in lecture.

Nicholas Le 4H

Adding on to the earlier response before me, the formula, Ke=1/2mv^2, is just a physics formula we used to find the kinetic energy of a system. In this case, we are trying to find the kinetic energy held by the released electron that is left over after subtracting the energy given by the light sourc...

Nicholas Le 4H

I was confused when to use the equation M1V1=M2V2 vs the equation molarity=moles/volume when doing dilution problems?

Nicholas Le 4H

Some of the solutions in the back of the textbook have different significant figures in their answers than what was given. An example would be that the given has three significant figures, while the solution in the back has four significant figures. Why is that if anyone knows?

Nicholas Le 4H

It might appear on the test just as an equation to be used for another topic like limiting reagents.

Nicholas Le 4H

You can do any seven questions out of all the categories as long as it is on the topics that we have already covered in class.

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