CHEMISTRY COMMUNITY

Saman Andalib 1H

To find the reverse activation energy, you must first be told that the reaction is reversible, as otherwise it may take a completely different reaction pathway during the reverse reaction and the reverse activation energy cannot be calculated. If the reaction is reversible, you also must be given a ...

Saman Andalib 1H

Rank the following species in order of increasing reducing power going from their neutral to second oxidation state: Pt, Pb, Cu. How do we know this? As a general trend, the reducing power of an electrolytic half cell increases as the value of E cell decreases (can be thought of as becoming more neg...

Saman Andalib 1H

Rank the following species in order of increasing reducing power going from their neutral to second oxidation state: Pt, Pb, Cu. How do we know this? As a general trend, the reducing power of an electrolytic half cell increases as the value of E cell decreases (can be thought of as becoming more neg...

Saman Andalib 1H

Hi! The fundamental thing that you have to know is different between a bomb calorimeter and a normal calorimeter is that in a bomb calorimeter, the volume is held constant. This means that there is no work done in a bomb calorimeter, and therefore any change in the internal energy is dependant on th...

Saman Andalib 1H

Cell diagrams frequently follow the structure of solid|liquid|aqueous||aqueous|liquid|solid. If the liquid is H20, you need not include it in the diagram. The solids on the outsides of the diagram also may not be needed if one of the reactants is a solid already, so a conducting metal is not needed.

Saman Andalib 1H

Concentration has a profound effect on cell potential. They are related through the Nerst Equation, which states; E = E deg cell + ((RT)/(nF))lnQ Where E deg cell is the original cell potential, R = gas constant, T = temp, n = number of moles of electrons transferred in the reaction, F = Faraday's c...

Saman Andalib 1H

The unique rate of a reaction (for a reaction in the general form aA---->bB) is -(1/a)(dA/dt)=(1/b)(dB/dt). For that particular question, my guess would be that it is not included because we cannot accurately calculate (dA/dt) or (dB/dt) since we are given average rates of change rather than instant...

Saman Andalib 1H

This means that the reaction rate does not depend on the particular amount of a specific reactant (that is 0 order).

Saman Andalib 1H

You can do this by saturating the concentration of one of the reactants to the point where any subsequent increase in it will no longer affect the reaction rate. This will, therefore, relate any new change in the reactant rate to an increase in the other reactant, creating a pseudo-first order react...

Saman Andalib 1H

You have to be careful when comparing what the slopes signify when comparing the slopes of different order reactions. Remember that for a 0 order reaction, the axes are time and [Reactant] whereas the slopes of a 2nd order reaction graph are time and 1/[reactant]. Direct graphical comparisons are th...

Saman Andalib 1H

I dont expect there to be a question which explicitly asks us to derive a particular rate law, but knowing their derivations may be useful for more applied questions during which you may forget a particular formula. At that point, you could simply derive it and not miss unnecessary points :)

Saman Andalib 1H

The units for a 0th order reaction can simply be determined from setting the normal rate law units = to the rate constant times whatever reactant raised to whatever order the reaction is. For 0 order, [mols*L^-1*s^-1]=k[A]initial^0 (0 order reaction). This would simplify to [mols*L^-1*s^-1]=k(1) The...

Saman Andalib 1H

Cell potentials are a fixed property, so they do not depend upon the stoichiometric coefficients relating the number of electrons in each half reaction.

Saman Andalib 1H

You are correct, Wmax only is equal to -nFE when the temperature and pressure are constant. Remember that Wmax is derived from a reversible reaction, which must occur at conditions of constant temp and pressure.

Saman Andalib 1H

All of the aspects of Gibbs Free Energy including the Van't Hoff equation and other related formulas. I would expect that there may be some interwoven questions related to enthalpy and entropy woven in to the test as well.

Saman Andalib 1H

By Friday of week 7 is when my TA told me we will get them back by.

Saman Andalib 1H

Yes, you are correct. The formula is the summation of the bonds broken minus the summation of the bonds formed.

Saman Andalib 1H

The amount of available energy in a system which is available to do work.

Saman Andalib 1H

It means that temperature is maintained constant and that there is an infinitesimally small pressure difference, resulting in us having to use the integral to solve.

Saman Andalib 1H

When it says that there is work done onto a system, the value is positive. When it says there is work done by the system, the value is negative for the system.

Saman Andalib 1H

A state function is a function which does not depend upon the path taken to reach a particular final point. Observations of the behavior are valid by simply looking at the final and initial point. An example of a state property Entropy

Saman Andalib 1H

The important part of this question is that the block of ice is at 0 degrees Celcius, meaning that any increase in energy inputted would be used towards the melting of ice and the subsequent increasing of temperature of the resulting water.

Saman Andalib 1H

This equation was briefly mentioned in the derivation of the formula for the reversible, isothermic reaction formula to solve for the amount of work done by a system. The more important system to know in-depth is the work formula for a reversible reaction

w=-nRTln(Vfinal/Vinitial)

Saman Andalib 1H

By nature of the formula and the relationship PV=nRT, if the pressure of the system is maintained at a constant value, there can be no fluctuation in the value of V, therefore making delta V 0 and the overal p*deltav term insignificant.

Saman Andalib 1H

They are interchangeable terms only when the pressure of the system in question is constant.

Saman Andalib 1H

The general concept that is used here is heat lost by the copper= -heat gained by the water. In the formula, the only thing that is a little bit tricky is that you have to use (Tfinal-Tinitial) for the variable delta T, then use algebra to simplify the equation to solve for Tfinal.

Saman Andalib 1H

I don't think it should really matter, but for safety, I would be consistent with the units that were presented initially in the problem.

Saman Andalib 1H

Yes, heat capacity is an extensive property because it depends upon the amount of a certain substance there is present.

Saman Andalib 1H

If you are referring to its use in an ICE table, Kp can only be used when all of the values in the molecules represented in the equilibrium expression for that particular chemical equation are in the gas phase.

Saman Andalib 1H

The rule is that if the value of either Ka or Kb is less that 10^-3 so it is fine to disregard x for a value of 10^-4.

Saman Andalib 1H

As Dr. Lavelle depicted in class, the arrow in the chemical equation for any reaction involving a strong acid or a strong base is simplified as being one arrow because of the overwhelming skew it has to one side of the reaction. This does not mean that the reverse reaction is not occurring, but only...

Saman Andalib 1H

If the volume of a container decreases and pressure increases, a reaction will favor the side of the equation which contains less moles of gas because of the equations goal of reestablishing equilibrium.

Saman Andalib 1H

It is built off of the equation that Ka*Kb=Kw and if Kw is a constant, any increase in Ka or Kb respectively will lead to a decrease in the other variable in each case.

Saman Andalib 1H

You don't include liquids in your equilibrium expressions because they occur in such large amounts that they are considered the solvents of the chemical reaction. Any reaction that occurs using a liquid will not provide a large enough change to that liquids concentration so as to require us to inclu...

Saman Andalib 1H

When the volume of the container is decreased, the pressure in the container is therefore increased. This increase in the pressure will cause the reaction to shift towards the side of the chemical equation with fewer moles of gas. Therefore, the equation will shift towards the products. When the tem...

Saman Andalib 1H

The value of Pi and ADP are equivalent to the reduction in the amount of ATP because they are represented with a stoichiometric coefficient of 1 in the equation ATP <--> ADP + Pi. Similar to when we calculated the amount of product created in a limiting reagent problem.

Saman Andalib 1H

It depends upon if the question initially gives you a Kc value, for which you would have to use concentration measurements, or if the problem gives a Kp value, for which you would use partial pressure measurements.

Saman Andalib 1H

They are both measurements of pressure in a system for the equilibrium expression. There is no difference in their usages in the context of a problem, but if you are converting from a concentration to a partial pressure (or vice versa), make sure that the constant R is in the correct units of either...

Saman Andalib 1H

When you are given concentrations, you must use the brackets as the notation. When partial pressures are given, the brackets are not necessary for writing the equilibrium constant expression.

Saman Andalib 1H

Yes, it is very common for Professor Lavelle to ask us to find the oxidation of a particular transition metal in the context of a coordination compound. These can normally be algebraically solved for, but you do need to know the oxidation states of some common ligands.

Saman Andalib 1H

It's important to know that polyprotic acids and bases have the ability to accept/donate more than one hydrogen ion. These polyprotic acids and bases have the ability to have a much stronger effect on the resulting solution pH, as they can greatly influence the hydrogen ion concentration within a pa...

Saman Andalib 1H

If an acid's corresponding conjugate base depicts resonance, it means that the resulting conjugate base is a more stable molecule, thus meaning that the original acid is a strong acid.

Saman Andalib 1H

Both versions can be used, as they simply relate to old and new regulations of naming coordination compounds.

Saman Andalib 1H

I am not sure about the first name that you wrote, but the following two are both accepted and are interchangeable. One is just by older coordination compound naming regulations and the other is not.

Saman Andalib 1H

In this class, we only have to worry about coordination compounds which have a mono-transition metalcore.

Saman Andalib 1H

Yes, it is highly unlikely for an amphoteric molecule to act as both an acid and a base at one time because it would require the simultaneous donation and acceptance of a hydrogen ion by that molecule.

Saman Andalib 1H

A chelate is formed when there are multiple polydentate anions bonding to a transition metal in a ring formation around it. Chelates are formed by polydentates, but not all polydentates contribute to the formation of chelates.

Saman Andalib 1H

A molecule is polydentate when it can bind at 2 or more different locations. These locations are determined if there are lone pair electrons available for coordinate bonding.

Saman Andalib 1H

You name the ligands in a coordination compound in alphabetical order.

Saman Andalib 1H

To denote that the lone pair that is active in bonding is located on the Oxygen atom on H20.

Saman Andalib 1H

Not necessarily. Knowing the hybridization surrounding a particular atom in a molecule tells you the number of regions of electron density around that atom. This allows you to know the initial VSEPR molecular geometry, but you cannot know the exact altered molecular shape unless you also know the nu...

Saman Andalib 1H

The sp2 hybridized orbital would look like this: p _ sp2 _ _ _ Three sigma bonds can be formed within the hybridized sp2 orbitals. The presence of the one excess p orbital allows for pi bonding to also occur. Conceptually, the easiest way to figure out whether sigma/pi bonding will occur is to look ...

Saman Andalib 1H

Since we have only slightly been introduced to this concept in the lectures, I do not believe that we will be asked to draw these on the exams. In spite of this, however, sigma bonds are bonds which are formed when the orbitals bond along a particular bonding plane. Pi bonds are formed when the bond...

Saman Andalib 1H

Correct, when all of the individual dipole vectors of a molecule cancel out, then the overall molecule is nonpolar.

Saman Andalib 1H

Essentially the two terms are opposites. Polarizing power is the ability for a certain cation to distort an anion. More positively charged cations such as Al3+ have a greater polarizing power compared to lesser charged ions. The tendency of the anion to become polarized by the cation is known as its...

Saman Andalib 1H

Whenever there is a lone pair present on the central atom of a molecule, the bond angles will always be reduced due to the repulsion which is now experienced as a result of the lone pair.

Saman Andalib 1H

The VSEPR model is a tool primarily used for the identification of molecular shape and orientation based upon the number of bonding and lone pairs present in a molecule. The tricky part with the VSEPR model is actually memorizing the names of all the shapes and what number of bonding and lone pairs ...

Saman Andalib 1H

Radicals would occur if an atom becomes an ion and has an odd number of electrons. In addition, in the bonding of a particular molecule with an odd number of atoms, radicals frequently occur. It is standard procedure to assign radical electrons to an element in a particular molecule that would lesse...

Saman Andalib 1H

It means that that particular element has empty subshells. The subshells always exist for the n=4 energy level, they just may not always be filled depending on the element.

Saman Andalib 1H

8 questions, each with multiple parts. The test in total is 110 points, accounting for 22 percent of our overall grade.

Saman Andalib 1H

After the first ionization energy, the element has now become a charged ion which has a high attraction between the protons in the nucleus and the electrons. Attempting to remove another electron is much more difficult than removing the first (higher ionization energy) because you now have to counte...

Saman Andalib 1H

No, we are not required to know the charges (valence electrons) of the D-block elements because they have ranging values.

Saman Andalib 1H

All equations in this chapter use kilograms because it is the SI base unit. In addition, in any equation which deals with Joules, kilograms is always used for the mass in order to make sure that the units of both cancel.

Saman Andalib 1H

Electrons always aim to find the lowest energy state in their respective orbitals. Electrons in elements such as Chromium and Copper remove an electron from the 4s orbital and add it to the 3d orbital because having all the orbitals in the d subshell half-full has a lower energy requirement than hav...

Saman Andalib 1H

The shielding effect basically describes the reduced attraction of a nucleus to its electrons the more filled energy levels there are. For example, in terms of electron ionization energy, it would be much easier to remove an electron from Potassium (4s1) rather than Lithium (2s1) because of the grea...

Saman Andalib 1H

Think about simple ratios when dealing with limiting reactant questions. The easiest way is to convert both reactant quantities into moles of the particular product that we are solving for. This will allow you to easily observe which one of the reactants produces the least amount of product and is, ...

Saman Andalib 1H

Light is the most general form through which photons are transmitted. The only necessity for electrons to be emitted from the metal is that they are struck with a ray of a particular FREQUENCY of energy. If that can be transmitted through mediums other than light, then yes. But light is the most cla...

Saman Andalib 1H

As Lavelle stated in the lecture, the experimental design in the experiment included calculations which discounted the velocity which is obtained from the opposite charges attracting the electron to the detector.

Saman Andalib 1H

You can turn in questions that are shown in both outline 1 and 2

Saman Andalib 1H

In short, yes, the two notations mean the exact same thing. Anything raised to the negative 1st power will always go to the denominator, making the two short-hands directly interchangeable. There have been no instances in which I have seen that there makes a significant difference when one notation ...

Saman Andalib 1H

Generally, you want to use exact values through the entire calculation until you reach your final answer. When you get to the final answer, you notate it according to the number with the least number of significant digits in the entire problem. Hypothetical Example: 2.37 x 2.5 = 5.925 Lowest number ...

Saman Andalib 1H

There are many free PDFs of the solution manuals available online that can be found with some deep web hunting. I wouldn't recommend paying the sky-high price of the manual for something you won't even look at for more than a minute at a time. If you need the PDF, let me know.

Saman Andalib 1H

When I begin to balance a chemical equation, I balance elements that only appear once on both sides of the chemical equation first. When there are two unique elements that appear once on both sides of the chemical equation, begin with the gaseous element (when hydrogen is present, balance it last ou...

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