CHEMISTRY COMMUNITY

Aman Sankineni 2L

The molecularity of a reaction is defined as the number of molecules or ions that participate in the rate-determining step.

Aman Sankineni 2L

Absorption is the process in which a fluid is dissolved by a liquid or a solid (absorbent). Adsorption is the process in which atoms, ions or molecules from a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent.

Aman Sankineni 2L

As you increase the temperature the rate of reaction increases. As a rough approximation, for many reactions happening at around room temperature, the rate of reaction doubles for every 10°C rise in temperature.

Aman Sankineni 2L

The pre-exponential factor (A) is part of the Arrhenius equation, which was formulated by the Swedish chemist Svante Arrhenius in 1889. The pre-exponential factor is also known as the frequency factor and represents the frequency of collisions between reactant molecules. Although often described as ...

Aman Sankineni 2L

The equation ln(k2/k1)=-Ea/R*(1/T2-1/T1) should be able to be used.

Aman Sankineni 2L

I think this should help in explaining it.

https://www.chemguide.co.uk/physical/ba ... enius.html

Aman Sankineni 2L

Since both K and Cl would dissolve in the water, they wouldn't be present in the half-reactions.

Aman Sankineni 2L

I think you need to use 10^-14 because that's where you would compare ph 14 and 1. If you use that in the denominator and numerator you should get +.828 and -.828, respectively.

Aman Sankineni 2L

Catalysts are present as reactants in the very beginning and products at the end. Intermediates, on the other hand, are not present in the initial reaction but are produced within one of the steps and then consumed within another step. Also, catalysts are used throughout the reaction. So according t...

Aman Sankineni 2L

I think this explains it well:
https://chem.libretexts.org/Bookshelves ... rown_et_al.)/19%3A_Chemical_Thermodynamics/19.7%3A_Free_Energy_and_the_Equilibrium_Constant

Essentially they are all linked through an equation.

Aman Sankineni 2L

I think the reason why O2 and H+ are on the same side is because the reaction would not be oxidizing if it was either
H+ -> O2 or
O2 -> H+
The equation has to be H2O -> O2 + H+ because then the reaction will be oxidizing for H in H2O -> H+

Aman Sankineni 2L

Whenever the anode/cathode has no solids in its half-reaction.

Aman Sankineni 2L

The phases are usually given in the equation. You can use those same ones in writing the cell diagram.

Aman Sankineni 2L

This is more of a conceptual question. The chapter itself talks about it in the last section, so we probably just have to understand the general idea.

Aman Sankineni 2L

We use k vs k' to differentiate between the rates for forward and reverse reactions.

Aman Sankineni 2L

5G.21 Calculate the equilibrium constant at 25 8C for each of the following reactions, by using data in Appendix 2A: (a) the combustion of hydrogen: 2 H2(g) 1 O2(g) Δ 2 H2O(g) (b) the oxidation of carbon monoxide: 2 CO(g) 1O2(g) Δ 2 CO2(g) (c) the decomposition of limestone: CaCO3(s) Δ CaO(s) 1 CO2(...

Aman Sankineni 2L

The standard state is 298 K or 25 degrees C.

Aman Sankineni 2L

Concentration cells are of two types: 1. Electrode concentration cells: In these cells, the potential difference is developed between two electrodes at different concentrations dipped in the same solution of the electrolyte. For example, two hydrogen electrodes at different gaseous pressures in the ...

Aman Sankineni 2L

An oxidizing agent is the substance that causes the oxidation in another substance. Common oxidizing agents include oxygen, hydrogen peroxide and halogens. A reducing agent is a substance that causes another substance to reduce. So to identify an oxidizing agent, simply look at the oxidation number ...

Aman Sankineni 2L

The standard Gibbs free energy of molecules is 0 for any element in its standard state.

Aman Sankineni 2L

No work is being done at equilibrium so the delta G value is 0.

Aman Sankineni 2L

The difference between the two is that delta G naught is at standard conditions. The reason Professor Lavelle emphasized it is because delta G naught is always the same because it is referring to when the reactants/products are at standard temperature/pressure. As the rxn goes towards equilibrium, d...

Aman Sankineni 2L

Yes, since entropy is a state function, the second law can be applied to irreversible reactions.

Aman Sankineni 2L

The difference between the two is that a regular calorimeter is simply a "thermally insulated container" while in a bomb calorimeter, the reaction takes place in a sealed metal container that is immersed in water in an insulated container.

Aman Sankineni 2L

Calculating the Q value with partial pressures gives you an answer without units. Therefore, it isn't necessary to convert the values in bars.

Aman Sankineni 2L

How do we tell if a reaction does expansion work or not?

Aman Sankineni 2L

Yup, both would be negative.

Aman Sankineni 2L

C in C∆T is heat capacity, while C in mC∆T is specific heat (Cs). C = mass x Cs, so those two equations are essentially equivalent. You use heat capacity when you don't have a total mass. That is if you know the total mass of the system, you can use the specific heat capacity. In most problems where...

Aman Sankineni 2L

Heat transfer to a system is positive, and heat transfer from a system is negative. W is positive if work is done by the system, and negative if work is done on the system.

Aman Sankineni 2L

I think the table on this page does a good job of answering your question, though it also depends on temperature:

https://opentextbc.ca/introductorychemi ... erature-2/

Aman Sankineni 2L

To get energy density in kJ/L from kJ/L, you divide the amount of energy with the mass of one mole of TNT and multiply it by the density of TNT. The answer should be 23.9 x 10^3 kJ/L.

3292 / 227.13 x 1650=23.9 x 10^3 kJ/L

Aman Sankineni 2L

I got 490 J as well. I believe the answer in the book is wrong.

Aman Sankineni 2L

I found this online: "Degeneracy plays a fundamental role in quantum statistical mechanics. For an N-particle system in three dimensions, a single energy level may correspond to several different wave functions or energy states. These degenerate states at the same level are all equally probable...

Aman Sankineni 2L

The heat of the reaction is equal to the negative heat of the calorimeter because the calorimeter is gaining heat from the reaction. Hence to calculate heat gained by the calorimeter, we use C(delta T). The question asks for the internal energy change for the reaction of 1.00 mol CO. We are given 1....

Aman Sankineni 2L

Basically, because hydroiodic acid is a strong acid, it dissociates completely in an aqueous solution. This means that the hydronium concentration is equivalent to the initial molarity of the acid. The back of the book represented this value in micromoles, so instead of just writing it as 6.0x10^-5,...

Aman Sankineni 2L

That is correct the O2 and N2 are diatomic gases in their most stable form and thus their standard enthalpy of formation is zero. Using the enthalpies of formation we calculate that CO2 requires -393.51 kJ/mol while H20 requires -241.82. Given TNT's enthalpy of formation we calculate: 28(-393.51 kJ/...

Aman Sankineni 2L

q is the amount of heat transferred to a system whereas is used to describe the change in enthalpy. Enthalpy is the total potential energy of a system, which is associated with the heat transferred to/from a system (q). However, at constant pressure which can make it difficult to see the difference ...

Aman Sankineni 2L

Enthalpy is equal to the system's internal energy plus the product of its pressure and volume. In a closed system, the heat absorbed or released equals the change in enthalpy.

Aman Sankineni 2L

Yup, you assume that its a cylinder.

Aman Sankineni 2L

a. 343 degrees K
b. 373 degrees K

Aman Sankineni 2L

As long as pressure is at 1 atm and the temperature is 25 degrees Celsius, the reaction is in standard state.

Aman Sankineni 2L

The standard enthalpy of formation is the change in enthalpy that accompanies the formation of one mole of the compound from its elements. The standard enthalpy of reaction occurs in a system when one mole of matter is transformed by a chemical reaction.

Aman Sankineni 2L

To start this problem, you would need to convert the pH into molarity by using 10^-4.60. Then, set up an ICE table with the molarity found as the H3O+ equilibrium concentration. Set the initial condition of HClO to x then subtract the molarity found from that, which will be the final equilibrium of ...

Aman Sankineni 2L

A change in pressure or volume will result in an attempt to restore equilibrium by creating more or less moles of gas. For example, if the pressure in a system increases or the volume decreases, the equilibrium will shift to favor the side of the reaction that involves fewer moles of gas.

Aman Sankineni 2L

If buffer questions were covered in either the chemical equilibrium or acids/bases outlines, then we probably have to know them.

Aman Sankineni 2L

Yup, temperature is the one thing that would affect the K value.

Aman Sankineni 2L

B) C) D) are weak so you can calculate their pH using a regular ICE box.

A) is a strong acid so its pH is simply -log(0.00005)

Aman Sankineni 2L

Q, which is the reactant quotient, is used to identify the direction of the reaction. By comparing the Q value, which is found with the same equation as the K value, with the K value, you can identify the direction. If Q < K then the reaction proceeds forwards but if Q > K then the reverse reaction ...

Aman Sankineni 2L

Q is mainly used to determine the favored reaction direction. It doesn't necessarily signify that the reactants or products have a higher or less concentration than one another.

Aman Sankineni 2L

A large equilibrium constant favors the products of dissociation, which means F2 would tend to split apart into two F and is therefore unstable. So, in comparison, Cl2 is more stable.

Aman Sankineni 2L

The equilibrium constant would be smaller with a higher concentration of reactants since the reactants make up the denominator of the formula.

Aman Sankineni 2L

By definition, the equilibrium constant has no units, as we're supposed to be using active masses instead of the molarity/ concentrations of the respective substances.

Aman Sankineni 2L

Any element beyond Na would have the exception.

Aman Sankineni 2L

I think it depends on your TA.

Aman Sankineni 2L

Yup, bent and AX2E

Aman Sankineni 2L

I hope he ends up curving the class.

Aman Sankineni 2L

Why does the lewis structure for ClF4+ place a formal charge of -1 on the central Cl atom when you could double bond one of the F atoms and move the formal charge of -1 to one of the non-central atoms?

Aman Sankineni 2L

The definition of amphoteric is a species that is able to act as both a base and acid, which means it should be able to accept and donate a proton when need be. The easiest way to remember is if the elements in question are part of the metalloid oxides section of the periodic table as opposed to the...

Aman Sankineni 2L

He will probably ask questions about acid/base strength based on the list given. As long as you know how to find strength, you would be able to answer the questions based on those 7.

Aman Sankineni 2L

Acids and bases containing carbon are known as organic. Acids and bases that DO NOT contain carbon are known as inorganic.

Aman Sankineni 2L

A coordination complex is the product of a Lewis acid-base reaction in which neutral molecules or anions (called ligands) bond to a central metal atom (or ion) by coordinate covalent bonds. Compounds that contain a coordination complex are called coordination compounds. Ligands are Lewis bases - the...

Aman Sankineni 2L

EDTA is used for chelation therapy. Chelation means "to grab" or "to bind." When EDTA is injected into the veins, it "grabs" heavy metals and minerals such as lead, mercury, copper, iron, arsenic, aluminum, and calcium and removes them from the body. It is used to treat...

Aman Sankineni 2L

Is SO3(2-) polar or nonpolar?

Aman Sankineni 2L

Molecular size determines intermolecular interaction strength. Since Iodine is a larger atom than Fluorine, it has stronger intermolecular strength and therefore a higher melting point.

Aman Sankineni 2L

The questions on the syllabus from 3F, 2E, and anything that covers sigma and pi bonds, so 2F.1 will cover topics on the test.

Aman Sankineni 2L

If the formal charges should be on the atom with the greatest electronegativity, then shouldn't the double bonds be to one oxygen and one sulfur? Then the other two oxygen would both have a formal charge of -1.

Aman Sankineni 2L

That would create a formal charge of -1 on both the single-bonded oxygen and sulfur. If you put double bonds on all of them, it would create a formal charge of -2 on the central sulfur. Isn't that identical in terms of formal charge?

Aman Sankineni 2L

What is the lewis dot structure for a thiosulfate ion? I drew it with a Sulfur in the middle with double bonds to three oxygen and the other sulfur. This would give the central sulfur a -2 formal charge.

Aman Sankineni 2L

CO has 10 valence electrons in total. A triple bond would be 6 electrons and a lone pair on both the C and the O would add another 4, making 10 total while also fulfilling the octet rule for both.

Aman Sankineni 2L

CCl4 has a tetrahedral shape that is symmetrical. Therefore, the bond polarity is canceled out.

Aman Sankineni 2L

How does the rotation of various energy orientations work in dipole-dipole forces? Essentially, what does the explanation for figure 3F.5 mean?

Aman Sankineni 2L

Why does the strength of the interaction in dipole-dipole forces depend more heavily on distance than the strength of interaction in ion-dipole forces?

Aman Sankineni 2L

Does a larger extent of hydration mean a stronger intermolecular attraction?

Aman Sankineni 2L

What do you do for exceptions? Such as in an atom consisting of N and O, which would be the central atom? O technically has the lower ionization energy than N. Does the number of desired bonds matter when considering the central atom more than the electronegativity? I believe the atom with the lowe...

Aman Sankineni 2L

Also, is test 2 worth the same amount as test 1?

Aman Sankineni 2L

The viscosity of a fluid is a measure of its resistance to deformation at a given rate. Liquids with high viscosity have more of a resistance to deformation.

Aman Sankineni 2L

Polarizing power follows the same trend as electronegativity while polarizability follows the trend of atomic radius.

Aman Sankineni 2L

Giving electrons is a lot stronger than sharing electrons.

Aman Sankineni 2L

What's the way Lavelle taught us how to solve it?

Aman Sankineni 2L

Ionization energy: the energy required to remove an electron from a neutral atom.
Electronegativity: the ability of an atom in a molecule to draw bonding electrons to itself.

Aman Sankineni 2L

The answer is 3956 m/s.

Aman Sankineni 2L

How can you tell that the transition is in the Lyman series from the fact that it is in the ultraviolet spectrum of atomic hydrogen? Lyman series are the only series found in the ultraviolet spectrum of atomic hydrogen. By knowing that the transition is in the ultraviolet spectrum allows us to know...

Aman Sankineni 2L

SammiOrsini_1B wrote:I think i am a little confused too. I thought there were 10^-9 meters in a nanometer and 10^-12 meters in picometer.

This should be right. Use dimensional analysis with these numbers in order to convert from meters to nanometers/picometers.

Aman Sankineni 2L

If we're writing a larger p-orbital values, can we use a noble gas to substitute? Ex. [Ne]3s^1

Aman Sankineni 2L

The double bond consists of two types of bonds, the pi bond and the sigma bond. The sigma bond is stronger than the pi bond which results in a shorter bond length. As for a triple bond, there are two pi bonds and one sigma bond, which results in an even shorter bond length. What is the difference b...

Aman Sankineni 2L

I don't exactly know what questions will be asked about the two but they are different. Ionization energy refers to the amount of energy necessary to remove the outermost electron of an atom or molecule. Electron affinity refers to the amount of energy necessary for a neutral ion to gain an electron...

Aman Sankineni 2L

Nathan Rothschild_3D wrote:I would recommend doing it on the chemical bonds section but since part of this last week included the quantum realm, it should still be okay to do some problems from that section.

From what I've seen, this is right. It should be okay to do problems from either section.

Aman Sankineni 2L

504939134 wrote:Covalent bonds can only be formed by nonmetals, and metals are more likely to form ionic bonds. Remember that metals often times become cations because it is easier for them to give up electrons. Non metals have high ionization energy.

Nonmetals can also form ionic bonds, right?

Aman Sankineni 2L

I believe they are used in more complicated experiments and more detailed chemistry, but in terms of this class, we probably won't be going over them since those elements don't come up.

Aman Sankineni 2L

When two electrons are parallel, both will be having the same spin or both going up/going down. When two electrons are paired, they will have opposite spins, one going up and one going down. If two electrons are in the same orbital they will always have opposite spins (paired). If they are in two di...

Aman Sankineni 2L

"Exceptions are based on the fact that half-full or full shells or subshells are more stable than partially filled ones. When the difference in energy levels between two subshells is small, an electron may transfer to the higher level shell to fill or half-fill it. The electron occupies the hig...

Aman Sankineni 2L

Ohhhh, just got it. Thank you!

Aman Sankineni 2L

b) First, you convert mg to g 5.00 mg * (1g/1000mg) = 5.00 x 10^-3 g of Na Since, it's asking for the how much energy is emitted by an excited SODIUM, you use the molar mass of Na 5.00x10^-3 g Na * (1 mol Na/ 23g Na) * (6.022 x10^23 atoms Na/ 1 g Na) = 1.31 x10^20 atoms of Na (1.31 x10^20 atoms Na)...

Aman Sankineni 2L

You can find your grades on the study list on myUCLA. Next to each class is a link to your grades for that class.

Aman Sankineni 2L

Getting a good night's sleep is important and helps me with anxiety before tests.

Aman Sankineni 2L

Velocity is a product of wavelength and frequency in terms of wavelength.

Aman Sankineni 2L

Is it usually safe to have four decimal places for calculations and answers?

Aman Sankineni 2L

How often do I tell chemistry jokes? Periodically!

Aman Sankineni 2L

Yup, that's what I got too.

Aman Sankineni 2L

Because it is just the percentage of mass of oxygen, then the original mass of 8.61g copper(II) chloride tetrahydrate doesn't matter. No matter how many grams of the sample you have the percentage mass of oxygen should always be the same because of the molar ratios. Correct me if I'm wrong! Yup, th...

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