CHEMISTRY COMMUNITY

Connor Chappell 2B

The wording is key. if the concentration of one of the electrode solutions is increased, then the concentrations between the two cells are more different (i.e. further away from equilibrium). However, increasing the mass of the electrode does not necessarily increase the concentration, in fact, incr...

Connor Chappell 2B

The first order and zero-order integrated rate laws are designed to create a linear plot, using a different y-axis depending on the order of the reaction. While the two graphs can look similar in that they are both decreasing lines, the clue to what order the reaction is is in the y-axis. If it is f...

Connor Chappell 2B

yes, the instantaneous rate is always its maximum value in the initial stages when you have your initial concentrations of each reactant and are ready to conduct the experiment. As the reaction approaches equilibrium, the instantaneous rate of the reaction decreases, and the rates of the forward and...

Connor Chappell 2B

yes, since when both concentrations of both reactants are doubled, this results in a doubling of the overall rate, both reactants are first order independently. Thus, when adding together n and m from k[A]^n[B]^m, 1+1=2, so it is overall a second-order reaction.

Connor Chappell 2B

Within the scope of this class, we will be asked to find the order of reactions based on experimental data, which is the example with multiple experiments where the concentrations of each reactant varied between each experiment and this resulted in a differing rate of the overall reaction.

Connor Chappell 2B

If a substance is reduced or oxidized but does not change state (i.e. Fe3+(aq) reduced to Fe2+(aq) by gaining 1e-), then a solid Pt(s) conducted should be used. C(gr) could also be used.

Connor Chappell 2B

You can combine different values (i.e. pressure and concentration) because K is a unitless value. Therefore, if you're given concentration of some solution and pressure of a gas, you can use both to calculate Q, if they are involved in the equation for such calculation.

Connor Chappell 2B

Liquid is placed in between s and g in the cell diagram.

(s)|(l)|(g)|(aq)||(aq)|(g)|(l)|(s)

Connor Chappell 2B

Pt should be used in the cell diagram when there is either the oxidation or reduction of some substance without a change in phase/state. (i.e. if Fe3+ is reduced into Fe2+ by gaining an electron, but both are in solution, a Pt electrode would be placed in the solution to conduct the electron into so...

Connor Chappell 2B

Standard Free energy change units are either Joules per mole or Kilojoules per mole.

Connor Chappell 2B

You can derive these half-reactions by the change in oxidation states of both of the species in the reaction. You notice that in the reaction given, Br is neither oxidized nor reduced, and Ag is being both oxidized and reduced in the reaction. Therefore, Ag is both the oxidizing and reducing agents,...

Connor Chappell 2B

The process of choosing which side the reaction will occupy in the cell diagram is the same regardless of the type of cell whether it is Galvanic or Electrolytic. However, conceptually, it is important to note that an input of energy will be needed for electrolytic cells regardless because they are ...

Connor Chappell 2B

I believe it depends on who your TA is. If they are on Chem community often, they may check at certain weekly deadlines but others may just check to see if you met 50 posts at the end. The best advice would be to ask your TA in particular.

Connor Chappell 2B

Reactions that are carried out quickly (i.e. those with short reaction times) are said to be kinetically controlled while those carried out over longer periods of time are said to be thermodynamically controlled.

Connor Chappell 2B

It should be based on state, so it should be s|g|aq||aq|g|s

Connor Chappell 2B

Many of the compounds that we deal with in redox reactions contain oxygen, hydrogen, and/or a transition metal, as well as common group 1 elements. Memorizing that Oxygen is 2- and the group 1 elements are +1 can help you identify the oxidation states of the other elements in the compound.

Connor Chappell 2B

Usually, a compound that contains both hydrogen bonds and loan pairs can go through autoprotolysis, as this is the proton transfer between two of the same molecules.

Connor Chappell 2B

A single line between compounds on the same side of a double line indicates a change in the physical oxidation state of the compound. For example, solid Fe being oxidized into Fe^2+ in solution would be denoted as { Fe(s)|Fe^2+|| }.

Connor Chappell 2B

J/C is used to indicate the potential difference because a Columb is defined as the amount of charge in 6.24x10^18 electrons. Therefore, the potential difference is defined as the energy transferred between two compounds per Coulomb of charge.

Connor Chappell 2B

It would most likely be safer to indicate the oxidation state of the compound especially in the instance of dealing with metals.

Connor Chappell 2B

When work is done on the system, work is positive. This is due to the fact that the reaction's capacity to do work has INCREASED. The same can be said for a reaction where work is done on the surroundings and the sign is negative because the reaction has lost energy to its surroundings in the form o...

Connor Chappell 2B

An adiabatic process is one in which no heat is transferred between the reaction and the surroundings (i.e. q=0). This is not the same as an isothermal process, in which the change in temperature is 0. Simply because there is no change in temperature, this does not indicate that there was no heat tr...

Connor Chappell 2B

Multiplying a reaction by some constant is the mathematical equivalent of raising the power of the Kc of said reaction to that same constant.

Connor Chappell 2B

If the change in gibbs free energy is negative, the reaction is spontaneous. If it is positive, it is not. It the change in gibbs free energy is equal to 0, the reaction is in equilibrium.

Connor Chappell 2B

We did not cover any new material on Monday. Lavelle decided to review 3 past exam questions in preparation for the midterm exam.

Connor Chappell 2B

Under constant pressure, some of the heat can go into doing work in order to expand or compress against the surroundings. Under constant volume, no work can be done.

Connor Chappell 2B

Basically, a reversible process is one in which the pressure of the system is equal to that of the surroundings. THIS HAS IMPLICATIONS when we describe the system using thermodynamics. When pressure is equal in a system and its surroudings, any infinitesimally small change in either the internal or ...

Connor Chappell 2B

Work done on a system by its surroundings is positive. Work done by the system on its surroundings is negative. This has to do with the fact that when a system does work, it loses energy (negative), and when work is done on a system, its energy increases (positive).

Connor Chappell 2B

There is a constant on the equations sheet on Lavelle's class website that has the conversion between Joules and L.atm

Connor Chappell 2B

When work is done on the surroundings, work is negative. The negative sign is used to indicate that the system is losing energy to the surroundings through doing work (you get tired when you constantly have to push against something that is pushing in on you). When work is done on a system by the su...

Connor Chappell 2B

Closed systems can be changed by changing either the temperature, pressure, or volume of the given closed system. No matter can flow in and/or out of a closed system, but energy can still be transfered between the system and its surroundings.

Connor Chappell 2B

No, technically we are still talking about topics in the realm of thermochemistry, and 4f is focused on topics that lay in thermodynamics. So no, we have not covered the material necessary to complete those problems.

Connor Chappell 2B

These are considered to be fundamentally differnet constants, given and acquired through different sets of conditions. Cvm is under constant volume, while Cpm is under conditions of constant pressure.

Connor Chappell 2B

I feel that he used the integral as a conceptual device to be able to reveal the idea he was trying to portray with the sum of infinitesimal changes in volume. Under constant pressure, P can be pulled out of the integral as a constant, and the change in V will be left as the product of the integral ...

Connor Chappell 2B

Heat capacity is the amount of heat needed to change the temperature of a substance by 1 degree C. The specific heat capacity yields the heat needed to raise the temperature of 1g of a substance by 1 degree C.

Connor Chappell 2B

Reducing the reactant induces the reaction to produce more of the reaction in order to balance out the system and achieve the same ratio at equilibrium.

Connor Chappell 2B

Ka is the acidity constant, and Kb is the basicity constant.

pKa = -log(Ka)
pKb = -log(Kb)

Connor Chappell 2B

The problem given on the tests gives you the chemical equation and the delta H value (change in enthalpy) and you are asked whether the reaction is endothermic or exothermic. If delta H is negative, the reaction is exothermic, and the contrapositive is true.

Connor Chappell 2B

The best way to be prepared for his lectures is just to follow the readings he assigned on the syllabus. Lavelle was explaining that the order in which he is going to teach us thermochemistry and thermodynamics differs from the order that the topics come in, in the book

Connor Chappell 2B

No, Ka and Kb values will be provided. It may be wise however, to be comfortable writing out chemical equations for the dissociation of acids and bases in water.

Connor Chappell 2B

The conventional scale of ph being between 0 and 14 is dewrvied from reactions with water at room temperature.

Connor Chappell 2B

I am saying that the function for giving ka is set up the same way as kc or kp. However, you are correct in that you need to set up an ICE chart to be able to represent the function for ka as a quadratic function solving for x.

Connor Chappell 2B

THe scale is not restricted between 0 and 14 for pH or pOH. However, at room temperature, this scale is restricted. This is because the value of kw (autoprolysis of water) is 10^-14 and thus, the maximum valuue is set to be 14, with the lowest value being 0. In many of the cases, we are assuming tha...

Connor Chappell 2B

A reaction that is endothermic requires heat to occur. Therefore, if we were to heat this reaction, it would favor the production of the reactions products, as sufficient heat is being applied to the system in order to elicit a reaction.

Connor Chappell 2B

You will want to try and idenitfy ka or kb depending on whether the substance is a acid or base. ka is calculated the same way that kc or kp would be calculated, ([P]/[R] excluding liquids or solids). And there are a few important equations associated with ka and kb. - (ka)(kb) = 1.0 x 10^-14 - pka ...

Connor Chappell 2B

The Reaction quotient Q is a number representative of what stage a reaction is at relative to its equilibrium conditions. Q can be used as a checkpoint in such a manner and will allow us to make predictions about which direction the reaction will tend to proceed. In order to do this, K will usually ...

Connor Chappell 2B

In the scope of this class, when asked to calculate the pressure of a substance, you will be given a temperature and a relative concentration of this substance and will be expected to know how to manipulate the Ideal Gas LAw equation in order to solve the relation between concentration and pressure ...

Connor Chappell 2B

PV=nRT This equation is used to convert between partial pressure of a gvien substance and the concentration of this same substance. This would be useful if we were given Kc and the partial pressures of certain substances and asked to solve for the unknown concentration of some substance. This is now...

Connor Chappell 2B

This principle tries to minimize the effect of change by shifting the direction of the reaction in order to maintain equilibrium Just to clarify, it can shift either way right? Yes, if the concentration of products was increased, which could happen in the real world, the reaction would respond by f...

Connor Chappell 2B

The General Idea of Le Chatelier's principle is that a given system will respond to changes in the system so as to minimize the effects of said change. This entails a number of different characteristic responses to different types of changes in the system (Temperature, Volume, Concentration, etc.). ...

Connor Chappell 2B

The answer to your question is found in the equation PV=nRT, which can be rewritten as P=(nRT)/V. n/V is the mathematical notation for concentration, therefore P = (concentration)(RT). Thus, the reason that concentration of a substance does not change in a beaker when the pressure is increased by ad...

Connor Chappell 2B

And it also may be worth noting that when dealing with changes in concentration of certain gases (pressures etc.), only increasing pressure by decreasing volume will have an effect on the concentration of the compound. If pressure is increased by adding an inert gas, as Professor Lavelle made note o...

Connor Chappell 2B

The concentration of liquids (solutes) and solids are not included in the calculation of the equilibrium constant because of the inability to apply this characteristic to these phenomena and have it possess and plausible meaning. Solutes, in a reaction at equilibrium, have an insignificant change in...

Connor Chappell 2B

The activity of a substance, denoted as sub j, is the effective equilibrium concentraiton of that substance in a given reaction. The activity coefficient is the ratio of the activity and concentration of the substances in a given reaction.

Connor Chappell 2B

A way to think about Q is a checkpoint to check where the reaction is at in the process of nearing equilibrium. (i.e. if Q<K, there is still more reactant that is being reacted to form the product. if Q>K, there is more product than the reactant would produce at equilibrium and thus, the reaction wi...

Connor Chappell 2B

Yes, if there is a high concentration of intitial reactants, the reaction will favor the production of the products in the reaction. It is also important to note that the value of the equilibrium constant (Kc or Kp) will not change, as the ratio of reactants to products will stay the same, despite t...

Connor Chappell 2B

Bar is a unit used to denote the partial pressures of gases in a given reaction. Another possible unit to represent a homologous gaseous reaction could be atmospheres. (atm)

Connor Chappell 2B

Gases in which the molecules do not interacti with each other or take up any space are characteristic of ideal gases. If that helps.

Connor Chappell 2B

How do we access Sapling plus if we bought the textbook package off of the UCLA bookstore and not the link that Professor Lavelle had provided?

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