CHEMISTRY COMMUNITY

Zubair Ahmed 1L

k' represents the rate of the reverse reaction and A represents the frequency factor.

Zubair Ahmed 1L

Molecularity only has to do with the reactants of a reaction. It has to do with how many atoms are colliding with each other at the same time.

Zubair Ahmed 1L

Yea we will be given this information in the context of the problem.

Zubair Ahmed 1L

Catalyst is always at the beginning of an equation and then used up while an intermediate is formed during a reaction and then used up again.

Zubair Ahmed 1L

in order to calculate the Ecell of a system, you must use the standard reduction potentials and the formula Ecell=cathode-anode.

Zubair Ahmed 1L

You would only add an inert electrode such as platinum(Pt) when there are no solids present in the reaction.

Zubair Ahmed 1L

The graph of a second order reaction is a positive slope of k when plotted on the graph of1/[A] vs time.

Zubair Ahmed 1L

I usually attend Lyndon's review sessions on Mondays. He provides great insight and detail on all the topics we are currently learning and his worksheets are very helpful as well. Moreover, I normally do all the practice problems on the outlines Dr.Lavelle has on his class website. Those are really ...

Zubair Ahmed 1L

Melody P 2B wrote:Would you add Pt(s) to both sides?

You would add Pt(s) to any side that does not have a solid. This allows electrons to be transferred.

Zubair Ahmed 1L

You will only need to include H+ and OH- in the cell diagram; exclude water.

Zubair Ahmed 1L

Yes, you will need an inert electrode such as platinum when there is a gas and aqueous molecule in the cell diagram because there needs to be a metal present in order for the electrons to be transferred.

Zubair Ahmed 1L

There are many equations in which you can use to solve for delta G. It all depends on what information you are given in the context of the question.

Zubair Ahmed 1L

The anode is is usually placed on the left side while the cathode is placed on the right side. The anode oxidizes the material present and the cathode reduces the material present. Electrons flow away from the anode and into the cathode.

Zubair Ahmed 1L

Yes, delta G is a state function. We can take a similar Hess's Law approach when trying to calculate the Gibbs free energy of a reaction. Another approach we can take to calculate the change in Gibbs free energy is by subtracting the total Gibbs Free energy of the reactants from the products.

Zubair Ahmed 1L

The purpose of a salt bridge/porous disk is for the ions to transfer and help maintain a neutral solution.

Zubair Ahmed 1L

According to Lavelle's email, we should be doing homework problems relating to Gibbs Free energy.

Zubair Ahmed 1L

It is very important to know the difference between. 5/2R is used for constant pressure and 3/2R is used for constant volume. You will have to use either one depending on the context of the question.

Zubair Ahmed 1L

I have never really come across any question where I had to use this equation. It is basically another way to state the fact that delta U=0 for an isothermal, reversible expansion. You might want to learn it just in case.

Zubair Ahmed 1L

Since entropy is a state function, you can simply add the entropy of the change in volume and temperature to find the total change in entropy of the system.

Zubair Ahmed 1L

If the reaction is endothermic, increasing the temperature will lead to an increase in product formation. If the reaction is exothermic, an increase in temperature will lead to an increase in of reaction formation.

Zubair Ahmed 1L

A key difference between reversible and irreversible expansion is that a reversible reaction does more work than an irreversible reaction. Also, in the real world, irreversible reactions are much more realistic.

Zubair Ahmed 1L

The equation "q = nC∆T" refers to the molar heat capacity because it measures the heat required to raise 1 mol of a substance by 1 degree celsius. We can ignore the "n" in the equation for the calorimeter because we are looking for the heat capacity instead.

Zubair Ahmed 1L

Since the question is asking for concentration values, the units for your answer should be molarity, mol/L.

Zubair Ahmed 1L

Dr. Lavelle mentioned on his website that the midterm covers everything we learned so far till the end of entropy.

Zubair Ahmed 1L

Yea we get them back in discussion this week!

Zubair Ahmed 1L

An isolated system juts implies that that there is no exchange of energy or matter with the surroundings. An isolated system could have a constant volume but it is not necessary.

Zubair Ahmed 1L

The pKa and the pH represent two different things. The pKa is the -log(Ka) and can be used to determine the strength of an acid. On the other hand, the pH is the -log(H+) concentration.

Zubair Ahmed 1L

Kc and Kp do not represent the same thing. Kp refers to the equilibrium constant using partial pressures while Kc refers to the equilibrium constant using concentration values.

Zubair Ahmed 1L

Yes, you would ignore the change in acid when the Ka value is less than 10^-3 because it is considered a weak acid and the change in concentration is so small that it can be ignored.

Zubair Ahmed 1L

It is a great to know a common list of strong acids and bases for the test but it is not required. It is important to know that if the Ka/Kb value is less than 10^-3 it is a weak acid/base.

Zubair Ahmed 1L

Le Chatelier's Principle refers to the process of chemical reactions adjusting to minimize the affect of certain changes. Moreover, exothermic means that heat is released as a part of the reaction and endothermic means that heat is required for the reaction to proceed.

Zubair Ahmed 1L

Both Q and K use the same equation during calculation. However, K is used at equilibrium while Q can be used at any point during a reaction. It is important understand the fact that Q can be changed due to changes in pressure and concentration but K does not. K shifts only when there is a change in ...

Zubair Ahmed 1L

Only temperature can affect the K value

Zubair Ahmed 1L

The Kc of the reverse reaction is the reciprocal of the forward reaction. For example, if the Kc of the forward reaction is 5, the Kc of the reverse reaction is 1/5.

Zubair Ahmed 1L

megangeorge-1K wrote:For this week should we be submitting homework from chapter 12?

We can choose Hw questions from either Chemical Equilibria or Acids and Bases outlines.

Zubair Ahmed 1L

ICE Tables are specifically used to find the equilibrium concentration of products and reactants when given the initial concentration. The value of the products will not always be zero. It will be values given from the question.

Zubair Ahmed 1L

The values of the change in concentration of solids and liquids are so small that they can be ignored when solving for the equilibrium constant.

Zubair Ahmed 1L

The Kc is representative of both the forward and reverse reactions because they reaction rates are reciprocals of one another.One way to visually see this is by solving for the K value of both reactions and you will see that the two rates are the inverse of one another.

Zubair Ahmed 1L

K represents the equilibrium constant which is denoted by the concentration of products over the concentration of the reactant. If both of the concentrations are the same, the K value would be one.

Zubair Ahmed 1L

Both have the same formula, but they calculate different things.

Zubair Ahmed 1L

I believe you are. However, you do not need to memorize ligand notations such as edta, ox, en, etc.

Zubair Ahmed 1L

I believe it is that all Bronsted acids and bases are Lewis acids and bases, but not all Lewis acids and bases are Bronsted acids and bases.

Zubair Ahmed 1L

HF is considered a weak acid due to fluorine's high electronegativity. Acids are considered strong when they completely dissociate in water and have longer, weaker bonds.

Zubair Ahmed 1L

Yea we have to memorize them. However, he said that we do not need to memorize notations such as edta, en, ox, etc.

Zubair Ahmed 1L

In order to determine if a molecule is polar or non-polar, you can draw out the lewis structure and identify the dipole moments of the given molecule. If the dipole moments cancel, the molecule is non-polar. If the dipole moments do not cancel, the molecule is polar.

Zubair Ahmed 1L

There are 2 pi bonds and one sigma bond in a triple bond.

Zubair Ahmed 1L

The book uses the "-ido" suffix when naming coordination compounds, but Dr. Lavelle use the suffix "-o". They are both technically correct but I would use the notation Dr. Lavelle uses.

Zubair Ahmed 1L

Either notation is acceptable but Dr. Lavelle mentioned that he prefers the d orbital to placed at the end.

Zubair Ahmed 1L

Dr. Lavelle mentioned that it does not matter which notation you use when writing out the d-block in hybridization, but he did say that he will be writing it as sp^3d in lecture.

Zubair Ahmed 1L

We typically indicate dipole moments by drawing an arrow towards the partial negative end of a molecule. If arrows cancel out, we know hat the molecule in non-polar.

Zubair Ahmed 1L

In a double bond there is one pi bond and one sigma bond. In a triple bond, there is one sigma bond and two pi bonds now due an additional side-to-side overlap.

Zubair Ahmed 1L

I would study both outline 3 and 4 just to be safe.

Zubair Ahmed 1L

Elements that contain a d-orbital can have expanded octets.

Zubair Ahmed 1L

To indicate a dipole moment, you need to draw an arrow pointing towards the most electronegative element.

Zubair Ahmed 1L

Boron is an exception to the octet rule, just like any other element in group 13 such as Aluminum.

Zubair Ahmed 1L

When drawing Lewis structures for ions, it is best of the central atom to have a formal charge of 0 and to place any negative charge on the outer elements because that is when it is most stable.

Zubair Ahmed 1L

Yup, just one more test and then the final.

Zubair Ahmed 1L

Just to reiterate, the central element is typically the least electronegative atom and a good way to check that is to calculate the formal charges of all the elements in the molecule.

Zubair Ahmed 1L

Arlene Linares 3A wrote:For the midterm, does anyone knows how much the units are worth when graded?

I believe both units and sig figs are each worth one point.

Zubair Ahmed 1L

I typically include double bonds to lower the formal charge of the an element. It is important to remember to not exceed 4 bonds per element unless the element can have an expanded octet such as sulfur and phosphorous.

Zubair Ahmed 1L

When I draw out Lewis structures, I count all the numbers of valence electrons in the given molecule and follow the octet guidelines given to us by Dr. Lavelle. I calculate formal charge when I need to draw out the lowest energy Lewis structure.

Zubair Ahmed 1L

Just to reiterate, resonance structures are basically lewis structures that can be written in multiple forms, the difference being the arrangement of the bonds between each resonance structure. The chemical properties are all the same.

Zubair Ahmed 1L

Phosphorous can have 5 bonds since it is in Period 3 and the d-block is included within it. As a result, it has 10 valence electrons and can create 5 bonds.

Zubair Ahmed 1L

When dealing with Lewis structures, the atom with the lowest ionization energy would be used as the central atom. Hydrogen is never the central atom so it would be Carbon in this case.

Zubair Ahmed 1L

Just to reiterate, nonmetals(anions) cannot become cations due to their high electronegativity and lack of electrons in their valence shell. Nonmetals such as chlorine with 7 valence electrons only needs one more electron to complete their octet so they would attract other elements in giving up an e...

Zubair Ahmed 1L

Yes. Basically, know what all the quantum numbers are and what they mean and know how to use them to label a given orbital.

Zubair Ahmed 1L

No, the 3d orbital would still be considered to be at a a lower energy level than the 4s orbital regardless whether or not the 4s orbital is completely filled.

Zubair Ahmed 1L

The De Broglie equations includes the mass and velocity of a given particle while the normal wavelength equation can also be associated with light. You can tell which equation to use in a given situation based upon the parameters listed in the question.

Zubair Ahmed 1L

mostly all the equations we were taught in the quantum world chapter use kilograms as the unit for mass since kg is the SI unit.

Zubair Ahmed 1L

yes, E represents the amount of energy per photon. The units for E is Joules.

Zubair Ahmed 1L

Yea make sure to only do questions from the Quantum World chapter. I asked my TA the same question and he made it very clear to not do problems from the Fundamentals section nor from the Chemical Bonds section because we have not covered it yet.

Zubair Ahmed 1L

Light cannot gain mass when it is stagnant because the particles are always in constant motion.

Zubair Ahmed 1L

In our case, the thing being quantized is energy. When energy is quantized, energy is packaged into small discrete packets of energy called quanta.

Zubair Ahmed 1L

Yea, it should be a whole number. The questions are usually phrased in a way in which the multiple of of the molecular to empirical formula is easy to work with. However, there may be examples where the multiple is "3.99" or "4.02". In this case, you would round to the nearest wh...

Zubair Ahmed 1L

Yes, periodic tables will be provided during the exam.

Zubair Ahmed 1L

I asked him this same question as well! For this quiz specifically, we do not need to know the names of specific cations and anions. He said that the way we will eventually memorize them is over time by practicing questions and solving problems. It will become second nature to us.

Zubair Ahmed 1L

From the equation, c(speed of light, 3*10^8 m/s)=lambda(wavelength, nm)*v(frequency, Hz), you are able to figure out many different variables and understand conceptual topics. For example, the speed of light, "c", is always a constant. This tells us that if that if the wavelength increases...

Zubair Ahmed 1L

As long as you participate in any of the the given discussion topics or ask your own question a minimum of 3 times a week, you will receive a maximum of 3 points for the entire week for 10 weeks. Chemistry Community counts for 30 points of your entire grade for the quarter. The syllabus for this cla...

Zubair Ahmed 1L

I have the solutions manual for the 6th edition textbook and it is very helpful for me. It gives me the ability to check my answers and shows me the steps for certain questions I have trouble figuring out. It is a great way to understand new material as well if you want to get ahead and try new sets...

Zubair Ahmed 1L

For me personally, I start by balancing the gases and then make my way to the solids. It generally works and makes things easier for me.

Zubair Ahmed 1L

Hello,

Towards the end of the syllabus, Dr. Lavelle has a list of problems that need to be completed for homework every week. You can choose any of those seven to complete.

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