CHEMISTRY COMMUNITY

SnehinRajkumar1L

For 1st order reaction: ln[A] vs time is linear
For 2nd order reaction: 1/[A] vs time is linear
For 0th order reaction: [A] vs time is linear

SnehinRajkumar1L

Order of a reaction is the power dependence of the rate on the concentration of the reactants. Molecularity refers to the number of reactants present (unimolecular, bimolecular, etc.)

SnehinRajkumar1L

Based on concentration, one side acts as the anode and the other as the cathode. Thus, one of them is reduced and the other is oxidized, depending on which has a higher concentration and produces a current.

SnehinRajkumar1L

Oxidation numbers tell you which species is being reduced or oxidized. You determine the loss of electrons when you balance the half-reactions accordingly.

SnehinRajkumar1L

Yes, you can assume that. The volume and pressure return to the initial state.

SnehinRajkumar1L

You add platinum as an electrode when the reactants/products are not conductive solids.

SnehinRajkumar1L

Usually, you would add them to the side that needs oxygens. For example, reactions that involve MnO4 or Cr2O7, typically require the addition of water to the other side so that the number of oxygens are balanced. Use OH- when dealing with basic solutions. You would still add it to the side that need...

SnehinRajkumar1L

The rate-determining step would have the highest activation energy, so that would have the largest hump. I am not too sure how to differentiate between the other two steps.

SnehinRajkumar1L

You can still solve it using the same method. However, you would most likely need to know the order of the other species to solve for it or would need more algebra to go through the problem.

SnehinRajkumar1L

In your rate law equation, you'd multiply out the units of the reactants to find the units.

SnehinRajkumar1L

I believe they are given at the bottom of the equation sheet.

SnehinRajkumar1L

They are both the same thing. They turn chemical energy into electric energy.

SnehinRajkumar1L

For this question, you would want to find the least reduction potential as that implies that it is better as an oxidizing agent and thus will be better at reducing other compounds. What was your method for trying to solve this problem?

SnehinRajkumar1L

If you are talking about solubility, there are lists you can find online. I don't remember the pneumonics to know this, but certain metals such as silver and mercury do not dissolve in water.

SnehinRajkumar1L

Yes, I believe so.

SnehinRajkumar1L

Because he extended it, I think he will tell us in class what to study until. It will most likely still be the end of Outline 5 and all of the electrochemistry material.

SnehinRajkumar1L

When writing out a diagram, the || means a salt bridge and a | means an interface between phases or a porous disc. The hydrogen cell is on the left, so you'd first write the hydrogen cell portion: H2 (g) | H+ We use the bar here because both phases are interacting. Because Pt is used as the conducto...

SnehinRajkumar1L

A battery will always do work because it's potential must be positive for it to provide energy to do work in the first place. Energy leaves a battery when it is being used.

SnehinRajkumar1L

The Nernst equation relates the energy of a cell outside of standard conditions when the concentrations of the products and reactants change to energy in standard conditions. So, when there is a change in concentration, use the Nernst equation.

SnehinRajkumar1L

Yes, that is the convention when representing galvanic cells.

SnehinRajkumar1L

For irreversible expansion, the only thing that changes is the values of Stotal and Ssurr. In irreversible expansion, the change in entropy of the system is the same as Stotal. Calculate S using the equations for changes in volume, but Stotal = Ssystem because Ssurr is 0.

SnehinRajkumar1L

The pressure of a system and the ratio of products to reactants affects how much energy can be produced.

SnehinRajkumar1L

Maximum work refers to when a system is undergoing reversible expansion. that is when the maximum amount of work is done.

SnehinRajkumar1L

I think it has to be when entropy is 0, and q = -w. So, there is no change in internal energy and no change in entropy.

SnehinRajkumar1L

You would calculate it using the known oxidation states of elements. For example, O is typically -2, C is typically +4, etc. You can use this to calculate this by equating it to the total charge.

SnehinRajkumar1L

SnehinRajkumar1L

Delta U is the change in internal energy, whereas delta H is the change in enthalpy. I believe delta H is the total energy change, whereas delta U only accounts for the kinetic and potential energy of a system.

SnehinRajkumar1L

No, you must add the heat of phase changes. q = mC(Tf - Ti) only calculates how much energy it takes to increase a mass of a substance by a certain amount of degrees.

SnehinRajkumar1L

Say you have an exothermic reaction. If you increase the temperature, that means there is heat available to favor the endothermic reaction as that reaction requires heat. So, it will shift to the right side. If you decrease the temperature, that means that the heat lost needs to be replaced, and thu...

SnehinRajkumar1L

A calorimeter is an apparatus that measures heat involved in a chemical reaction. To calculate the heat of reactions, you can use heat capacity and the relationships between heat absorbed and lost.

SnehinRajkumar1L

You should assume constant pressure.

SnehinRajkumar1L

Equilibrium by definition means something is reversible and happens in both directions. In terms of thermodynamics, we are talking about internal and external pressure being equal.

SnehinRajkumar1L

Degeneracy refers to the possible states an object can have. So, the greater the degeneracy, the greater the entropy of the system.

SnehinRajkumar1L

Reversible expansion always does more work than irreversible expansion. Additionally, the internal and external pressures are equal in reversible expansion.

SnehinRajkumar1L

Since enthalpy involves reactions, volumes are bound to change.

SnehinRajkumar1L

Standard Reaction Enthalpy is the heat given off or taken up during reaction. Enthalpy of formation is difference between the standard enthalpies of products and reactants.

SnehinRajkumar1L

yes. Additionally, temperature and pressure should be at 25 C and 1 atm respectively.

SnehinRajkumar1L

The pressure of gases are at 1 atm and the temperature is 25 C

SnehinRajkumar1L

An increase in temperature leads to a change in enthalpy. Increasing temperature increases enthalpy, and vice versa.

SnehinRajkumar1L

There are 3 methods he described in class. You can add the bond enthalpies between the molecules and do broken - formed. If you have 2 reactions, you can add up the enthalpies to find the enthalpy of reaction for the combined one. Finally, you can use the enthalpy of formation to find it (products -...

SnehinRajkumar1L

State functions do not care about the process to get the value. As Lavelle said in class, because this doesn't matter, you can add them up since they are specific points.

SnehinRajkumar1L

I believe it is conjugate base/acid divided by the original compound.

SnehinRajkumar1L

A lot of it is the same. However, there will be a lot of working backwards (ex. using a Kb to find Ka for acid dissociation). Otherwise, most of the steps are essentially the same. If anything, you will have to write out the reaction yourself, requiring knowledge of common acids and bases and their ...

SnehinRajkumar1L

It is such a small quantity of the acid that there is not enough to completely change its pH.

SnehinRajkumar1L

I believe if the Ka for the second dissociation is small enough, you can ignore the second one because little to no acid will deprotonate.

SnehinRajkumar1L

Yes, sometimes. This goes back to 14A where we looked at bond length and electronegativity (for binary acids like HI and HF and bases like LiOH and NaOH), and the number of oxygens to compare oxoacids.

SnehinRajkumar1L

Le Chatlier's principle shows us how to evaluate where equilibrium lies in a reaction. It is qualitative and helps us determine whether products or reactants are favored.

SnehinRajkumar1L

Solids and liquids are typically in excess and thus tend to not change much in equilibrium.

SnehinRajkumar1L

No, because solids and liquids are always in excess. Thus, removing or adding it would not affect equilibrium.

SnehinRajkumar1L

K is the ratio of products to reactants. There are numerous ways to increase the rate of reactions, such as increasing temperatures.

SnehinRajkumar1L

I don't think higher pressure means that the equilibrium constant is larger. The constant is always set for a specific reaction regardless of pressure.

SnehinRajkumar1L

In order for it to form a coordinate compound, it has to be bonded to a transition metal.

SnehinRajkumar1L

No, the speed of protons cannot be the same as the speed of light. It is physically impossible for this to occur.

SnehinRajkumar1L

Well, in the case of the question, we can look at part a. You know that n = 2 and l = 1, meaning that it is in the p orbital. So, the orientation of the p orbitals doesn't matter and thus, there are 3 possible orbitals. For part b, there is only one that can have those three quantum numbers because ...

SnehinRajkumar1L

Trichloroacetic acid is stronger. The Cls bonded to the molecule in place of the hydrogen has a greater electron-withdrawing power contributing to anion stability when it loses the proton.

SnehinRajkumar1L

No. Strong acids and weak acids are determined by bond length for binary compounds and electron-withdrawing power. An exception to the trend you noticed is H2SO4, which when it dissociates, becomes HSO4-, but is still a strong acid.

SnehinRajkumar1L

Nitrogen is monodentate. The Nitrogen's lone pair is considered.

SnehinRajkumar1L

The longer the bond, the stronger the acid.

SnehinRajkumar1L

Bases produce conjugate acids and acids produce conjugate bases. If the acid is a strong acid, its conjugate base is a weak base and vice versa.

SnehinRajkumar1L

They react with fatty acids on the surface of your skin and produce the soapy feeling.

SnehinRajkumar1L

Are there any examples of a compound that is a Bronsted acid/base but not a Lewis acid/base and vice versa?

SnehinRajkumar1L

Yes, I think it is still cation before anion.

SnehinRajkumar1L

Basically, a chelating ligand is one that can bond multiple times to the central metal ion by forming a ring with it. This is a result of the ability to rotate about sigma bonds so that the ligand can conform its shape to create that structure.

SnehinRajkumar1L

In organic acids, the hydrogen is bonded to an oxygen which is bonded to a carbon. So, the electronegativity of the oxygen is decreased because it is also sharing electrons with carbon, and thus, the hydrogen is harder to remove. With inorganic acids, the hydrogen is bonded to a highly electronegati...

SnehinRajkumar1L

I think the ones he went over in class will be good to review and know for tests, as he did go over them in-depth (cisplatin and myoglobin).

SnehinRajkumar1L

Strong acids and bases completely dissociates in water. Additionally, Ka and Kb (their respective equilibrium constants) will be really high because of this complete dissociation.

SnehinRajkumar1L

You can look at the electronegativity of the atoms and molecular shape/geometry.

SnehinRajkumar1L

Yes, H-bonds are a type of dipole interaction.

SnehinRajkumar1L

Molecules with dipole-dipole bonds have polarity on both molecules. However, with dipole-induced dipole bonds, the polarity of another molecule causes a temporary dipole to occur in another molecule. It is possible for a molecule to have both kinds of forces, it just depends on the orientation of th...

SnehinRajkumar1L

The molecular shape does not account for lone pairs of a molecule, but geometry does.

SnehinRajkumar1L

A --> Central Atom
Xn --> number of bonding electrons
En --> number of lone pairs

SnehinRajkumar1L

Any molecule can induce a dipole on another molecule. So, any molecule can have these dispersion forces.

SnehinRajkumar1L

C4H9OH forms hydrogen bonds with each other b/c of the OH group at the end of the molecule, and thus has a stronger bond between the molecules. CHI3 is more polarizable and thus has a stronger IMF.

SnehinRajkumar1L

Given the energy for exciting one electron, divide the energy absorbed by that value.

SnehinRajkumar1L

I don't think you can find the maximum wavelength. however, you can find the minimum wavelength by equating the energy of the light to the work function and solving for wavelength using the speed of light.

SnehinRajkumar1L

Yes, that is correct. The first one treats each bond as 1 electron, the other treats it as 2.

SnehinRajkumar1L

Yes, you can use it to calculate energy changes across energy levels.

SnehinRajkumar1L

Polarity is how charged an atom is. Polarizability is how likely it is to induce a dipole with another molecule. So the more polar a bond is, the more likely it is to polarize another molecule.

SnehinRajkumar1L

You can look at the rows they are in to determine which one is more electronegative.

SnehinRajkumar1L

The half-filled p orbital is more stable than the p orbital of oxygen. It is easier for an oxygen atom to lose/gain an electron to fill up the remaining unpaired shells as it is in a more unstable form.

SnehinRajkumar1L

One exception is for the ionization energy of group 15 and 16 elements. Although it typically increases across a row, the ionization energy of group 16 elements is actually less than group 15 elements because the half-filled orbital is more stable, and harder to remove an electron.

SnehinRajkumar1L

l corresponds to one of the s, p, d, or f subshells. So, based on that, you can determine the number of orbital.

SnehinRajkumar1L

It means that the electrons in bonds are not set. For example, with benzene, the double bonds in the ring are not set. There are other configurations of it, and so you shouldn't see it as one set bond arrangement.

SnehinRajkumar1L

Do problems from chemical bonds.

SnehinRajkumar1L

The number of valence electrons is 7 for manganese. It includes the 3d orbital electrons because the difference in energy between the 3d orbital and 4s is very small, so they essentially are in the same energy level. However, transition metals can have multiple valence states, so technically 2 or 7 ...

SnehinRajkumar1L

If I understand this scenario correctly, I would assume that the beam of light is ejecting an electron from the lithium and it is detected by the sensor. This essentially is the photoelectric effect, as you have light pointing at a metal that is causing an electron to be ejected. You are dealing wit...

SnehinRajkumar1L

It depends on which energy level the electron is in as well as the convention the problem uses when listing l values. The plane will correspond to the appropriate electron plane. I recommend watching the corresponding module for this lecture as he shows an example where he does just this.

SnehinRajkumar1L

You would solve this using the delta E equation. Substitute hv (Planck's constant * frequency) for delta E and set up the other side using the difference in energy (-hR/n^2-(-hR)/n^2). Plug in the appropriate numbers and solve. Don't forget to inverse and square root properly and you should get the ...

SnehinRajkumar1L

For this problem, you need two separate equations to answer both parts. For part a, the net ionic equation represents only the ions that participate in the reaction to form the precipitate. So, you would have one with copper and hydroxide on the reactant side, and on the other, the precipitate by it...

SnehinRajkumar1L

Calculate the frequency first using the wavelength of the light. Then, use that frequency to calculate the energy of an individual photon. Divide 32 by that value and multiply by 2 to get the number of photons emitted in 2 seconds. For the second part, divide by Avogadro's number to get number of mo...

SnehinRajkumar1L

Use the De Broglie wavelength equation to solve for the wavelengths of both. Then, divide the wavelength of the neutron by the proton's so that you get the percentage.

SnehinRajkumar1L

T is metric tons and it is 1,000 kilograms or 1,000,000 grams.

SnehinRajkumar1L

Catalysts typically lower the activation energy of a reaction so that it can happen faster. I assume that the catalyst does the same in that reaction.

SnehinRajkumar1L

What happens when the energy of the photon is equal to the work function? How is the electron emitted if there is no excess energy to be converted into kinetic energy?

SnehinRajkumar1L

2.9995 would be correct because you round to the appropriate number of sig figs.

SnehinRajkumar1L

Yes, the calculations would be for that. There might also be problems where they have you solve for the energies of a quantum level given the change in energy and the final or initial energy or solve for wavelengths, frequencies, etc. You can also look at the homework problems for the corresponding ...

SnehinRajkumar1L

First, you must solve for the new concentration after the florist dilutes it with 3 more liters of water. Using this molarity, you can calculate the number of moles each plant receives in the 100 mL. Now, for every mole of fertilizer, there are 2 moles of nitrogen. So, using this ratio, you can solv...

SnehinRajkumar1L

This equation demonstrates that initial and final moles are always equal when diluting a solution. So, yes, when you do multiply it out, the units for volume cancel out, but you are left with the number of moles. This equation helps us calculate volume needed for dilutions or new concentrations usin...

SnehinRajkumar1L

Net ionic equations only show the reactants that participate in the reaction. Since the reaction produces a copper hydroxide, the only reactants that matter are the copper and hydroxide. The sodium dissociates in the solution and does not contribute to the precipitate.

SnehinRajkumar1L

Hydroxide has a -1 charge. Group 2 elements (including calcium), always have a +2 charge. So, for the charges to balance you would need 2 hydroxide molecules for the calcium ion. This applies to Group 1 elements where they always have a +1 charge. Elements in group 13, 14, 15, 16, and 17 have a +3, ...

Search found 101 matches