CHEMISTRY COMMUNITY

Ronak Naik

The transition state theory states there exists a state between the reactants and products where the compound is in its highest energy form called the activated complex. This is different from the collision theory as it states that the more frequent collisions the reactants go through the faster the...

Ronak Naik

The order of a reaction signifies how the rate is dependent on the concentration of a reactant. Thus, a zero-order reaction means there is no dependence between rate of a reaction and concentration of a reactant.

Ronak Naik

I'm assuming we will have to print and then scan and send back as the problems will likely be free response. It would be very unlikely that he only asks for the final answer to be entered onto ccle. My guess is we will have to print it out and then scan and submit online so he can grade for partial ...

Ronak Naik

Electromotive force is a difference in the potential of two reactions that give rise to an electric current. This concept was given in the first lecture of electrochemistry.

Ronak Naik

1st: ln[A] = -kt + ln[A]o

2nd: (1/[A]) = kt + (1/[A]o)

0 order: [A] = -kt + [A]o

Ronak Naik

I had to look up the equations for an aluminum-air fuel cell because I couldn't find the cell equations, in the following pages after Focus six. anode: 6OH-(aq) + 2Al(s) --> 2Al(OH)3 (aq) + 6e- cathode: 3H2O(l) + (3/2)O2(g) + 6e ---> 6OH- (aq) overall: 3H2O(l) + 2Al(s) + (3/2)O2(g) --> 2Al(OH)3 (aq)...

Ronak Naik

at pH=1, the denominator in the K should be 1x10^-14 M, which will give you the right answer.

pH=1: RT/nF (lnK)= .025693 V ln(1.0 mol.L^-1/ 1.0 x 10^-14 mol.L^-1)= +0.828V

Ronak Naik

Borate is a polyatomic ion with a charge of negative one and thus we can assume that there is a transfer of only one electron and thus in the formula n=1.

Ronak Naik

I believe it is called tetramolecular; however, since the simultaneous collision is needed for the reactants to go forward with the reaction, it is very unlikely to have a tetramolecular reaction as four reactants colliding together is very rare.

Ronak Naik

Psuedo rate law means one that has been modified to fit a certain order that was not already in its desired order, to begin with. For example, a pseudo-first-order reaction is one that was not originally first order, but the concentration of the reactants is altered in order to make it a first-order...

Ronak Naik

The proportion of rate to concentration is the difference. In a first order reaction, the rate is proportional to the concentration. In a second order reaction, rate is proportional to the concentration raised to a power of two. Lastly, a third order reaction, the rate is proportional to a concentra...

Ronak Naik

Usually, the final redox reaction will have H+ in the reactants or products. When using the Nernst equation, set up the ratios of products to reactants for lnQ. Then, substitute given values for the reaction quotient but leaving [H+] as it is to solve for. Isolate [H+], and then take -log [H+] to ge...

Ronak Naik

Electromotive force is a difference in potential, for example, reduction potential that gives rise to some sort of electric current that can be used to do work.

Ronak Naik

The .0592 is used along with logQ, but the .025693 is used with lnQ. Both will give the same answer in the end.

Ronak Naik

Yes an ICE table is needed in part b. Once you find the moles of each substance using the given moles, use an ice table to find equilibrium concentrations.

Ronak Naik

Dispersal of the matter is the idea that in a system energy will be spread over many particles rather than being concentrated, thus, if the substance can be dispersed into particles it will be in order to follow the laws of energy and spread it out over a greater area. Since KNO3 is an ionic compoun...

Ronak Naik

I think for this one we should know that both H+ and O2 are on the same side of the reaction because together they form water which is the desired product on the right side of the equation. If either H+ or O2 was on the other side, the chemical reaction would not have made sense.

Ronak Naik

You have the numbers correct. but should double-check the arrangement of the final equation you are using to solve. Should be like this...

Ecell = E cathode - E anode (solving for E cathode...)
E cathode = E cell + E anode
E cathode = -.698V + .34V = -.349V

Ronak Naik

Higher cell potentials will indicate a greater level of spontaneity; however, spontaneity is a thermodynamic concept. It does not relate to kinetics, and thus, will not tell us anything about the speed of a reaction.

Ronak Naik

I believe you can assume that the cathode will always be on the right. But, just to double-check when you assume this, at the cathode the reaction that takes place is always reduction. Thus, we should see a gain of electrons on the right side of the given statement. In this one, Ag+ goes to Ag.

Ronak Naik

When we balance half-reactions, I'm confused on the order in which we should balance them. Do we add H+ or H2O first?

Ronak Naik

b) you simply use the equation deltaGf = -RTlnK. In the problem it should look like this

deltaGf = -RTlnK = -(8.314 J/K mol)(298K)ln(1.1E-12) = 68 kJ/mol
--K was given in the problem

Ronak Naik

A half-reaction is a partial breakdown of a full chemical redox reaction that shows each individual species being oxidized (loss of electrons, electrons on the product side) or being reduced (gain of electrons, electrons on the reactant side).

Ronak Naik

a) the delta G of formation for water is -228.57 kJ/mol.This should get you the correct answer when using it in the -RTlnK equation.

b) maybe recheck that you are using the correct delta G of formation values
CO2 --> -394.36 kJ/mol
CO --> -137.17 kJ/mol

Ronak Naik

I am not exactly sure, but the equilibrium constant, K, is a ratio of the products over reactants raised to the power of their respective molar coefficients. Thus, the moles of the product are already accounted for in the natural log of the equilibrium constant.

Ronak Naik

I think anytime there is no temperature we assume 25C (298K).

Ronak Naik

I think anytime there is no temperature we assume 25C (298K).

Ronak Naik

I believe because in the case of heat, as heat leaves the system entropy decreases which is absorbed by the surroundings. In general, what is lost by one is gained by the other part of a system.

Ronak Naik

Intensive properties are ones that depend on the size or amount of variables involved. Heat capacity depends on heat and temperature, both of which do not change in response to size of the system or amount of material. However, specific heat capacity depends on grams of a substance and molar heat ca...

Ronak Naik

When you solve for the moles given from the .113g you get 1.45x10^-3 mol. However, the chemical equation starts off with 2 mol of C6H6 and thus you must use stoichiometry to convert to the proper number of moles to get the accurate deltaH in the end.

Ronak Naik

It's fairly simple. The class is made up of homework points, discussion posts on chemistry community, and then the exams (Test 1, Midterm, Test 2, Final). The final grade has no weighted categories so it is simply how many points you earn out of all the total points possible in the class. The syllab...

Ronak Naik

The SI unit for entropy is J/K.

Ronak Naik

A compound can take many forms in which the atoms can have different placements. Each of the different positions the atoms can take makes up different microstates which all have the same energy.

Ronak Naik

Kinetics is the study of the rate of reactions and how they are dependent on certain factors such as heat and time. Thermodynamics relates more to looking at the initial conditions and final conditions of a reaction.

Ronak Naik

Delta G° represents the standard free energy of a reaction, which is the gibbs free energy, or the energy available to do work, at the standard conditions of a reaction. The other Delta G is at any other point in the reaction which can be increased or decreased depending on how much products or reac...

Ronak Naik

A state property is a quantity that is independent of how the substance was prepared. For example, pressure and volume are both state properties that do not have anything to do with how a sample is prepared. Heat would not be a state function as it is dependent on what type of reaction takes place.

Ronak Naik

Anytime you switch from celsius to Kelvin you must always use the conversion K=C + 273.

Ronak Naik

Titrations are used to find the concentration of an unknown acidic solution by adding known concentrations of a basic solution, or vice versa. The base is added to the solution while there is an indicator added to the acid so that when the acid and base reaction reach equilibrium, moles of acid equa...

Ronak Naik

The final solutions should be posted on his website but on the previous 14A website. I'm not sure if we have access to his 14A website anymore.

Ronak Naik

I think this may be a typo as the given concentration does not say X 10^-3. We can ask Lavelle or TAs in class tomorrow.

Ronak Naik

If the problem says a certain molarity of an acidic or basic solution it is referring to its initial concentration. If it was the equilibrium concentration, it would have definitely specified.

Ronak Naik

Since the values are given as gas pressures, you would just have to calculate Kp without converting it to Kc.

Ronak Naik

Le Chatelier's encompasses all three mentioned in relation to adding a stress or removing a reactant or product, whether it may be concentration or pressure. If a stress is added to a reaction, according to LeChatelier's principle, the reaction will move away from that stressor to regain equilibrium...

Ronak Naik

Yes that is correct. The higher Ka and Kb, mean that more of the acid or base dissociated, which indicates a higher strength. Due to the math, (log function), the pKa becomes the inverse and lower pKa and pKb values correspond to a greater strength.

Ronak Naik

I believe when considering LeChatliers principle, you must take into account all reactants and products. But, when writing the equilibrium constant equations, liquids and solids are not accounted for.

Ronak Naik

I think there is no official reason why it is 5%; however, the approximation check is used to make sure that X is such a small number that it allows to consider it insignificant when add or subtracting to another number.

Ronak Naik

I attached a picture of my notes.

Ronak Naik

The gas law is an expression that relates P and V to concentration. Thus it allows you to convert between partial pressures and concentration of a reactant or product that is in equilibrium during a reaction.

Ronak Naik

Solids and liquids are not used in equilibrium because they do not affect the reactant amount at equilibrium and therefore should not be expressed in the equilibrium constant.

Ronak Naik

Q and K are both calculated the same way — products/reactants. K is specifically referring to when the chemical reaction is in equilibrium. Q describes the reaction at any other point in time other than equilibrium.

Ronak Naik

In the problem, they will either give you the partial pressures of some of the reactants and products, which you would use to solve for Kp. If they give you the concentrations of the components of the reaction, then solve for Kc. Both are calculated the same way, products/reactants.

Ronak Naik

This principle states that if a side of a equation increases in concentration, then the reaction will shift toward the other direction. For example, if the concentration of the reactions is increased, the forward reaction will be favored to produce more product to maintain equilibrium. Likewise, if ...

Ronak Naik

Yes, sig figs is still used in pH and pOH calculations. However, the rules are slightly different. For pH and pOH sig figs are started to be counted after the decimal. For example, 6.5 pH is only 1 sig fig.

Ronak Naik

Looking at the chemical formula, pay attention to the anion. If the anion, is larger that means the bond between the elements is weaker. If the bond is weaker that means the acid will dissociate more, thus indicating it is a strong acid.

Ronak Naik

I don't think we will be expected to know solubility rules as none of the problems nor his lecture mentioned anything about knowing precipitation rules. Just to make sure, maybe we should clarify with him tomorrow.

Ronak Naik

The weaker the bond is the easier it is to break apart into ions and dissociate. We know that the more an acid dissociates the stronger it will be; thus, the fact that HCl has a weaker bond it will be able to dissociate easier making it the stronger acid. Similar to bases, the weaker bond the base h...

Ronak Naik

Yes this is correct. Any time the coordination complex has a negative charge you add -ate to the end of the name.

Ronak Naik

We don't neccessarily use one or the other to define them. A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. A Lewis acid is a electron acceptor and a lewis base is an electron donor.

Ronak Naik

We don't neccessarily use one or the other to define them. A bronsted acid is a proton donor, and a bronsted base is a proton acceptor. A Lewis acid is a electron acceptor and a lewis base is an electron donor.

Ronak Naik

I believe both of the examples you have given might be incorrect. The Cl is the anion and thus must be written outside of the big brackets.

Ronak Naik

When looking at the chemical name, the ligand will be the one that is written inside the parenthesis.

Ronak Naik

It would be really hard to distinguish from only the formula you would need to draw the lewis structure to find out if it has lone pairs.

Ronak Naik

Yes, there should be an online code that came with the book purchase. But, there was an exchange for the code you got for a new one. Check with the textbook renting center in ackerman to get some help with that.

Ronak Naik

Yes, the ion ion interactions could be on the test, but the main forces are dipole-dipole interactions, London Dispersion forces, and hydrogen bonding.

Ronak Naik

The molecule will be bent with bond angles slightly less than 120 degrees. Looking at the Lewis structure will tell you that this molecule has 2 bonding atoms and 1 lone pair, thus it is bent. If the molecule had 3 bonding atoms and 0 lone pairs, it would have been trigonal planar.

Ronak Naik

Steric # and coordination # are the same thing as they both refer to the number of bonded atoms and lone pairs around an atom.

Ronak Naik

If there is only one, simply writing just the letter X or E is enough. The subscript of 1 is redundant.

Ronak Naik

I'm almost certain the binding site will be on a protein of some sort.

Ronak Naik

You have to be careful because Lewis structures are not meant to be drawn to an accurate representation of the shape of a molecule. Although a Lewis structure may be drawn as symmetrical, we must first consider the VSEPR shape first. If we were to use the shape and symmetry of the VSEPR structure, t...

Ronak Naik

For an atom to have 120-degree bond angles, the molecule must be identified as trigonal planar. For this shape, the molecule must have one central atom and three surrounding bonded atoms. The molecule you have described only has two surrounding molecules and thus is not a trigonal planar with 120-de...

Ronak Naik

Yes, the presence of lone pairs usually renders a molecule to be polar since the atom with the lone pairs will be a more negative charge. Another example would be water!

Ronak Naik

Hi, let's take a trigonal planar molecule for example. As per your comment, if all the dipoles are facing outward meaning the more positive atom is on the center, then this symmetrical distribution of dipoles will render the molecule nonpolar. If even one of the dipoles was facing the opposite direc...

Ronak Naik

You have to predict its shape first using the rules we learned in the lecture. Then, you will know the bond angles. If the molecule is linear, then the angles will be 180 degrees. Trigonal planar - 120 degrees. Tetrahedral - 109.5 degrees.

Ronak Naik

There are no electronegativity exceptions to my understanding. Electronegativity increases going up a family and also increases going down a period towards Fluorine.

Ronak Naik

Yes, the d-block allows the elements that are at the far right of the periodic table to extend their octet as they will put the extra electrons in the following d orbitals.

Ronak Naik

If the molecule consists of two atoms and the electronegativity of one atom is significantly higher than the other, the molecule can be considered polar. For molecules with 3 or more atoms, drawing the structure and then writing the dipole arrows will allow you to assess if the molecule is polar.

Ronak Naik

Hello, when talking about single bonds, a greater difference in electronegativity is directly related to the strength in bonds. But, as you said, a double bond is stronger than a single bond, and thus, a triple bond is stronger than a double bond due to increased attraction between each atom.

Ronak Naik

Hello, compounds with Hydrogen bonded to N, O, F always have a hydrogen bond due to the high electronegativity from the anions. The electrons are pulled toward the anion and create a partial positive on the hydrogen atom. The partially positive hydrogen bond the bonds to the partially negative anion.

Ronak Naik

I am sure we will only need to write the formal charges if the problem asks which model is more favorable if there are resonance structures.

Ronak Naik

One of the TA's had mentioned a past exam question stating what is the probability of finding an electron in the center of a p orbital? The probability of this is 0 because a p orbital has 1 node (as well as a d orbital). Electrons cannot be found at the nodes only in the orbital space.

Ronak Naik

Oxygen only needs two more electrons to fill its valence shell and therefore it means that it has a high power to attract electrons in order to complete its final energy shell. Fluorine is the most electronegative atom since it only requires one more to fill its shell.

Ronak Naik

You would draw each ion separate in brackets next to each other. For example, the lewis structure for ammonium chloride would be as follows:

[*lewis structure for NH4+] [Cl-]

Ronak Naik

Hi, since Cl already has 7 valence electrons and O is more electronegative, the unpaired electron will be on the oxygen atom.

Ronak Naik

Chromium's d orbital technically rests in 3d4, however, due to electron stability, the element is more table when an electron from the s orbital is transferred into the d orbital to make the configuration 3d54s1. A half d orbital is more stable and therefore the s orbital will lose an electron that ...

Ronak Naik

Yes that is correct.The correct structure would be the one with the lowest formal charges. The other oones can be drawn to show your reasoning in order to prove that the lowest formal charges are the correct answer. However, the one to report as your final answer should be the one with the lowest fo...

Ronak Naik

Hi, I believe the online modules were only for week 1 and 2 material and nothing further than that.

Ronak Naik

Hi, when writing the electron configuration 3d actually comes first before 4s since 3d electrons are at a lower electron shell level.

Ronak Naik

Why does the trend going across a period start from bigger radii to smaller, and then once you hit the anions it again returns to a big radius and then decreases to small?

Ronak Naik

Yes, the R constant can only be used when dealing with Hydrogen as the constant was determined based on experimental data for H.

Ronak Naik

F orbitals have 3 nodal planes.

Ronak Naik

Yes, that is correct, the numbers do not play an important role in this situation. The only thing we need to pay attention to is the sign indicating the spin, the 1/2 value does not matter.

Ronak Naik

We would use this equation in questions that ask us about a change in energy levels (n1 to n2). i.e. How much energy is required to excite an electron from energy levels 1 to 4? If ##J energy were used to excite an electron off of ground state, what will be the final energy level of the electron?

Ronak Naik

When an atom is in the ground state it means it is in its lowest electron shell and has not been excited to a higher energy level. The way to get it out of the ground state is to excite the atom with a photon or heat.

Ronak Naik

Yes, that is exactly correct. The intensity of light is directly related to the number of photons not the common mistake of thinking about energy. Once enough energy from the photon has been put in, the electron will be ejected with a kinetic energy of 1/2mv^2. Each photon will eject one electron if...

Ronak Naik

The mass also has to be in kg because whenever doing a calculation it should always be done in SI units which for mass is kg.

Ronak Naik

Increasing light intensity will increase the number of photons. If the energy in the photon is sufficient enough to eject an electron then increasing the intensity will increase the number of photons, and therefore will excite a greater number of electrons.

Ronak Naik

IN the textbook, it talks about Balmer series as well as others. Each of them are given an "n" value. What does the n represent?

Ronak Naik

When a photon is shot at a metal surface, if there is sufficient energy the electron will be removed with a kinetic energy equaling 1/2 x (mass of e-) x (velocity of e-)^2.

Ronak Naik

Formula Units are used to denote an ionic compound. In an ionic compound, 1 mole of the compound has 6.022x10^23 formula units. In this problem. first find the moles of MgSO4 and then use Avogadro's number in a stoichiometric conversion to find the number of formula units.

Ronak Naik

Yes, they are similar. M and c both refer to the number of moles of solute divided by the total volume in Liters.

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