CHEMISTRY COMMUNITY

Suraj Doshi 2G

We can't use H+ to balance an equation in basic solutions as adding H+ would decrease pH (Making the solution overall more acidic) and therefore messing up the equation. To balance an equation in basic solution we would have to use OH- and then add waters to the other side to balance everything out.

Suraj Doshi 2G

What is the relationship between Boltzmann Distribution and the Arrhenius Equation?

Suraj Doshi 2G

Can someone explain the difference between adsorption and absorption as it relates to catalysis?

Suraj Doshi 2G

I would assume that we should know the basic idea, but we most definitely have to know the pre-equlibrium approach.

Suraj Doshi 2G

∆S = nR lnV2/V1 From the equation above, I believe you can find that when calculating for the entropy of a system itself, if V2 is greater than V1, the deltaS value will be greater than if V1 > V2. (This indicates expansion). If entropy of the system is increasing, then entropy of the surrounding wo...

Suraj Doshi 2G

The rate constant should still be K as none of the stoichiometric coefficients and concentrations will affect the rate of reaction.

Suraj Doshi 2G

Microscopic reversibility is when a reaction has the same intermediates in both the forward and reverse reactions.

Something along the lines of

A --- B ---> C
C --- B ---> A

(where B is an intermediate)

Suraj Doshi 2G

The degree sign (naught) indicates "at standard conditions" whereas without it conditions could be skewed.

Suraj Doshi 2G

After balancing the states of the compounds used should remain the same.

Suraj Doshi 2G

We must add solid platinum so that the electrons have something to bind to. Whenever no solid is present in the equations given, we have to include platinum.

Suraj Doshi 2G

From the equation deltaG = -nFE, we can determine if a reaction is favored or not.

If E (cell potential) is positive, deltaG is negative and thus will be spontaneous.
If E is negative, deltaG will be positive and therefore non-spontaneous.

Suraj Doshi 2G

This equation comes from separating the variables in the differential rate law and then taking its integral.

Suraj Doshi 2G

For the reaction given, the unique rate would be:

(-1/a)*(d[R]/dt) = (1/b)*(d[P]/dt)

Suraj Doshi 2G

the Nernst Equation relates cell potential with concentrations:

E = E^naught - (RT/nF)*lnQ

E^naught is the cell potential at standard conditions.
R = Gas constant
T = Temp in Kelvin
N = mols of e-
F = Faraday's constant
Q = Reaction Quotient

Suraj Doshi 2G

Galvanic cells are spontaneous reactions because cell potential is positive making deltaG negative (thus spontaneous) while electrolytic cells have negative cell potentials making deltaG positive (therefore non-spontaneous).

Suraj Doshi 2G

The values that are equal to zero in a reversible system are only deltaU and deltaH. (They equal each other)

Work can still have some value (nonzero) when the system is reversible.

Suraj Doshi 2G

An increase in the reaction quotient will lead to E becoming smaller which, I believe means that the more product we have, the cell potential would be decreasing.

Suraj Doshi 2G

If Ecell > E°cell what does this mean in relationship to deltaG. And likewise if Ecell < E°cell, what does this mean to deltaG?

Suraj Doshi 2G

For electrons to pass from one side to another, there must be a positive charge on one end. The salt bridge allows for ions to keep this positive charge to maintain electron flow.

Suraj Doshi 2G

These elements are typically uncharged and therefore do not have a nonzero oxidation number.

Suraj Doshi 2G

Depending on what you are solving for(enthalpy, entropy... etc) find the values for both the products and reactants, making sure to multiply by coefficients if necessary and to find the total, sum the products and then sum the reactants. Subtract the reactants from the products for the final answer.

Suraj Doshi 2G

The Van't Hoff equation is used to determine how temperature is affecting K. There are further derivations of the equation depending on which variables are known and constant. (A different equation for when deltaS is constant and when deltaH is constant)

Suraj Doshi 2G

When will work be equal to Gibbs free energy? (Which variables need to be constant for this phenomenon to happen?)

Suraj Doshi 2G

Is the Van't Hoff Equation only used when deltaG is zero?

Suraj Doshi 2G

The second equation is relating to deltaG when the reaction is at equilibrium. The first equation is used when the reaction is still unstable, or favors one side over another.

Suraj Doshi 2G

Why do more complex molecules have a higher S (as compared to simple molecules) if they are more ordered and structured?

Suraj Doshi 2G

I understand that in any spontaneous process, there is an increase in entropy. When referring to volume in this manner, is it standard that volume would have to increase to keep this statement true?

Suraj Doshi 2G

Can someone explain why entropy is an extensive property as opposed to a state property?

Suraj Doshi 2G

When the total change in entropy is equal to zero, this means that the system is at equilibrium.

Suraj Doshi 2G

It is referring to carbon in its graphite state.

Suraj Doshi 2G

The equation is used to find entropy using degeneracy.

Suraj Doshi 2G

What this is saying is that essentially, since we know that it is an isothermal expansion, the temperature is not changing while volume is increasing. For ideal gases, the change in internal energy is 0, therefore indicating that all the work done is converted into heat with no waste.

Suraj Doshi 2G

Standard enthalpy is describing the enthalpy of a given reaction when the pressure is at 1 atm and the products and reactants are in their standar states.

Suraj Doshi 2G

Standard enthalpy is describing the enthalpy of a given reaction when the pressure is at 1 atm and the products and reactants are in their standar states.

Suraj Doshi 2G

Since q is net heat gain/lost and w is net work done (either on or by the system) we can see that energy will be conserved through a totality of calculations done as either heat or work.

Suraj Doshi 2G

This phase change causes the change in enthalpy to be positive (delta H is positive).

Suraj Doshi 2G

Why does the temperature of a sample remain constant when it goes through a phase change such as vaporization, melting, or sublimation?

Suraj Doshi 2G

If the concentration of a reactant is increased, the reaction should typically proceed to the right (towards products). If the concentration of the products is increased, then typically the reaction will proceed in the reverse direction, towards the left (towards reactants).

Suraj Doshi 2G

A state property means that the value of the variable (in this case enthalpy) is determined by the current state of the substance. Since enthalpy can change, it is referred to as a state function because we must take into account the addition and subtraction that is associated with the calculations ...

Suraj Doshi 2G

All the state change enthalpies must be included. I believe Professor Lavelle was simply mentioning that the table given in the textbook gives enthalpies for gases, however if a reaction has another type of state change we must take that also into account.

Suraj Doshi 2G

High enthalpy indicates that more energy must have been put into a substance, therefore, making it more reactive. A more reactive substance would be relatively unstable therefore high enthalpy actually indicates low stability.

Suraj Doshi 2G

Since temperature is not changing, neither would the Kw. Therefore to find the concentrations of both ions, simply take the square root of the Kw to find the answer.

Suraj Doshi 2G

Inert gases are all the noble gases. These gases do not change the overall reaction and therefore are not included in the Kc equation.

Suraj Doshi 2G

To determine what change in pressure does to a system you have to look at the molar coefficients for each molecule on both sides of the equation. Depending on the change in pressure, if pressure increased, the system moves toward the side with lower total moles and vice versa to make up for the space.

Suraj Doshi 2G

They are calculated similarily in that they both use the [products]/[reactants] ratio. The difference is that for Kb you need to have the [OH-] in the numerator and for Ka you need to have [H30+] in the numerator.

Suraj Doshi 2G

I'm having a bit of trouble figuring out how to arrange the molecules for increasing base strength within problem 13. The problem states: Arrange the following bases in order of increasing strength on the basis of the pKa values of their conjugate acids, which are given in parentheses: (a) ammonia (...

Suraj Doshi 2G

Why does only a change in temperature change Kc whereas a change in pressure and/or volume does not?

Suraj Doshi 2G

K doesn't have units as the actual calculation comes from the chemical activity value. This value is a number without units therefore in the end, K does not have any units associated with it.

Suraj Doshi 2G

Why do we not include solids or liquids in the equilibrium concentration calculations?

Suraj Doshi 2G

What is the threshold that we can calculate for the change of X which makes a difference in the initial values of the reactant or product concentrations?

Suraj Doshi 2G

The only things that are included in the equilibrium equation are compounds/molecules that are either aqueous or gases. Therefore they would be included in the equation.

Suraj Doshi 2G

Weak acids and weak bases can neutralize strong bases and strong acids (respectively) if they are present in concentrations that allow them to do so. The concentrations can be determined by using the Ka equation.

Suraj Doshi 2G

The hypobromite ion would be stronger as it is the conjugate base of a weak acid thus making it a stronger base than morphine. We know that morphine is a relatively weak base as it contains a nitrogen with a lone pair.

Suraj Doshi 2G

A lewis acid will accept electrons whereas a lewis base will donate electrons. The product is generated depending on whether or not the acid and/or base that are reacting are strong or weak. a) PF5 = lewis acid, it accepts electrons from F- (lewis base) b) SO2 = lewis acid, accepts electrons from Cl...

Suraj Doshi 2G

Drawing the lewis structure would help because then we are able to see which atoms have lone pairs and thus we can see where the ligand will bind to the transition metal and how many bonds it will form.

Suraj Doshi 2G

1) Greek Prefix
2) TM cation name with roman numerals
3) Anion
4) Hydrate with proper prefix

Suraj Doshi 2G

When nonmetal oxides react with water, do they form strong or weak acids?

Suraj Doshi 2G

CO3 2- can be either monodentate or bidentate simply because the carbonate can occasionally bond to two metals. The metal that binds with the oxygens will use the lone pairs from two oxygens thus only two metals can bind in total to the oxalate ion. No other metal has fewer electrons that would allo...

Suraj Doshi 2G

Yes, amphoteric compouds must be oxides.

Suraj Doshi 2G

A lewis acid accepts electrons while a lewis base donates electrons.

Suraj Doshi 2G

We should know some of the main strong acids and bases from memory. These molecules completely deprotonate. With this logic, we can see if the molecule falls into one of these categories and if it does not then the molecule does not completely deprotonate.

Suraj Doshi 2G

The coordination sphere is made up of the central transition metal and the bound ligands attached to it. Thus the coordination sphere must include the ligands/bonded atoms.

Suraj Doshi 2G

The coordination sphere contains the ligands along with the central transition metal. It forms due to the geometry of the molecule.

Suraj Doshi 2G

This occurs because we have more s orbitals that end up contributing to electron repulsion which makes the bond angles increase.

Suraj Doshi 2G

SnCl2 should not have a radical as it has a total of 18 valence e-. The molecule itself should therefore not have a radical on it.

Suraj Doshi 2G

The oxygen has three regions of electron density thus we can determine that it will have a hybridization of sp^2.

Suraj Doshi 2G

When discussing repulsion strength between regions of electron density and atoms, how can we determine which repulsion forces (ie lone-lone PR, lone-bonding PR, bonding-bonding PR) are the strongest?

Suraj Doshi 2G

H20 would have 3 locations of electron density as we must take into account the lone pairs on oxygen. These lone pairs are what give water its bent shape.

Suraj Doshi 2G

I believe we have to look at the electronegativity between bonds and if the difference is greater than 0.4, then the bond is polar. If the difference is less than 0.4, then the bond is nonpolar. If there are no polar bonds, then the molecule as a whole should be nonpolar.

Suraj Doshi 2G

Yes, as they can alter the shape of a molecule when present.

Suraj Doshi 2G

The VSEPR formula follows: AXnE where A is the central atom, X is the number of bonded atoms to the central atom and E is the number of lone pairs. From this combination of numbers, we can draw the Lewis structure of the molecule and determine its shape.

Suraj Doshi 2G

I believe that this statement is correct as we would, in turn, have charges unevenly balanced within the molecule.

Suraj Doshi 2G

For the Heisenburg equation, the change is velocity is important because then only can we calculate the change in momentum(p) to eventually solve the whole equation.

Suraj Doshi 2G

We should not see this as the largest orbital possible is f and that has an angular momentum quantum number of 3.

Suraj Doshi 2G

Ionic bonds can have dipole moments.

Suraj Doshi 2G

Angular momentum is denoted by l.

l=0 is the s-orbital
l=1 is the p-orbital
l=2 is the d-orbital
l=3 is the f-orbital

Suraj Doshi 2G

I believe the two elements are commonly boron and aluminum as they need 5e- to complete their octet.

Suraj Doshi 2G

The ground state for Ga is [Ar]3d10 4s2 4p1. For the ion, the electrons are taken out of the s and p subshells as the electrons in these shells are further from the nucleus as opposed to the 3d10 electrons and thus the ion electron configuration for Ga3+ is [Ar]3d10.

Suraj Doshi 2G

Can someone explain what is meant by the idea that electrons in resonance structures are "delocalized"

Suraj Doshi 2G

I believe that specifically for this case, the hydrogen bonds to oxygen due to the strong covalent bond attraction. Since Cl is larger than O, the dipole-dipole attraction is weaker and thus hydrogen does not like to bond with chlorine.

Suraj Doshi 2G

A resonance hybrid is essentially a combination of all the resonance structures for a specific molecule. The correct resonance structure has the lowest formal charge.

Suraj Doshi 2G

I believe that this value is typically given when needed in a problem. It comes from experimentally performed data.

Suraj Doshi 2G

The five valence electrons come from the breakdown:

3e from the p-orbital and then 2e from the s-orbital.

I believe that for antimony the electrons are pulled from the s orbital too as they are further away from the nucleus.

Suraj Doshi 2G

Different resonance structures can and will have different energies associated with them. Stabler structures will have lower energies as opposed to unstable high energy structures.

Suraj Doshi 2G

The neutral electron configuration for Ga is : [Ar] 4d^10 4s^2 4p^1.

To make it Ga^3+, we would have to take away three electrons, thus we would take 1e from the 4p orbital and the other 2e would come from the 4s orbital leaving the configuration to be [Ar]3d^10.

Suraj Doshi 2G

The question is:

Place the following ions in order of increasing ionic radius: S^2-, Cl-, P^3-.

Why do they not all have the same ionic radius if they have the same number of electrons?

Suraj Doshi 2G

Can an two electrons within the same subshell have different energies associated with them?

Suraj Doshi 2G

Why are there two equations related to Heisenburgs indeterminancy?

One being: deltaP = (mass of an electron)*deltaX

The other being: deltaP * deltaX >= h/4pi

Suraj Doshi 2G

For both parts we can use the equation: c = (lambda) * (v-frequency).

The equation for part a turns out to be:
3.00*10^8 = (lambda) * 7.1 x 10^14 Hz.

The equation for part b turns out to be:
3.00*10^8 = (lambda) * 2.0 x 10^18 Hz.
Just be sure to convert to picometers.

Suraj Doshi 2G

When reading, we are exposed to natural visible light which is within the range of 400nm to 700nm. Thus, we can conclude that 600nm is some form of visible light and therefore pertains to the activity of "reading".

Suraj Doshi 2G

Schrodinger's equation allows for us to understand that the wave function of an electron is based on the principle quantum number (which determines energy and shell size), the angular momentum quantum number (which describes the shape), and the magnetic quantum number (which describes orientation).

Suraj Doshi 2G

According to the equation E = hc/(lambda) where E is energy, h is Planck's constant, c is the speed of light, and (lambda) is wavelength, we can determine that Energy is inversely proportional to wavelength. Thus a wave with a larger wavelength would yield a smaller energy and thus would not be able...

Suraj Doshi 2G

The limiting reactant will tell you how much of the final product will be able to form. It also tells you what reactant is in excess (if there is excess).

Suraj Doshi 2G

According to the equation E = hv, we can conclude that Energy (E) is directly proportional to frequency (v). If frequency (v) were to increase, then the Energy (E) would also increase and vice versa.

Suraj Doshi 2G

I just wanted to clarify something:

In the photoelectric effect, is it true that only high-frequency light(as opposed to low-frequency light) has enough energy (within the photon) to eject an electron from the surface it interacts with?

Suraj Doshi 2G

I would think that the molar ratio and the atom ratio are the same, so I do not think that it would be inaccurate. But when creating the molecular or empirical formula, you must have whole numbers denoting the number of atoms in a specific molecule.

Suraj Doshi 2G

I would presume that as a norm we would have to be able to convert from .001 to 1000 in the various calculations regarding mass, length, etc. But I'm not 100% sure.

Suraj Doshi 2G

Yes, it is easiest to use 100g as the sample mass for percent composition.

Suraj Doshi 2G

A medical researcher investigating the properties of intra-venous solutions prepared a solution containing 0.278 m C6H12O6 (glucose). What volume of solution should the researcher use to provide 4.50 mmol C6H12O6?

Would I use the formula MiVi = MfVf to solve this problem?

Suraj Doshi 2G

A student prepared a solution of sodium carbonate by adding 2.111 g of the solid to a 250.0-mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into a flask to obtain (a) 2.15 mmol Na2+; (b) 4.98 mmol...

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