CHEMISTRY COMMUNITY

Anish Natarajan 4G

If you're compressing a gas and the process is isobaric, then most likely the temperature is decreasing since the equation PV=nRT holds that if volume is going down (compression) and pressure is staying the same (isobaric), then either n, R, or T is going to change. R is a constant so we can rule th...

Anish Natarajan 4G

Generally it will be stated within the parameters of the problem whether or not pressure/volume is constant.

Anish Natarajan 4G

So far in the examples we've been given in lecture, the slow step has been explicitly labelled

Anish Natarajan 4G

If deltaS is less than 0, then that means that the overall change in entropy is negative--implying a decrease in spontaneity

Anish Natarajan 4G

Delta G0 is the Gibbs free energy of a reaction at equilibrium whereas delta G is the gibbs free energy of a reaction at any given state

Anish Natarajan 4G

Sure! The rate of a reaction is the speed at which a reactant degrades and is usually expressed in some mol/s or mol/L*s whereas the rate constant, k, is a constant with no units that is generally multiplied to a concentration to find out its concentration at an equilibrium. Rate=Rate constant*[reac...

Anish Natarajan 4G

Either can be used if there is no solid metal on either the anode or cathode

Anish Natarajan 4G

Basically what you want to do is split the reaction into two half reactions; add water and hydrogen/OH ions to either side to balance molecules and add electrons to either side to make the charges balance out. Then multiply either reaction by a coefficient to make sure that the # of electrons on eac...

Anish Natarajan 4G

To calculate it just substitute the value of the reactant concentration as it relates to t with 1/2[reactant]

Anish Natarajan 4G

Most likely not considering what we've covered in class

Anish Natarajan 4G

If you're given the reaction itself then you can just see the constituent reactants and determine the rate order just based on that, but you can also tell what order a reaction is based on the graphs of concentration over time (i.e. linear graph of ln[reactant] vs t is 1st order, linear graph of rea...

Anish Natarajan 4G

If the forward reaction is exothermic, then with an increase in temperature the reverse reaction is favored, meaning that k'>k

Anish Natarajan 4G

Delta U is the change in internal energy of a system, which is dependent on its temperature. If T=0 then Delta U=0

Anish Natarajan 4G

Depending on the pressure, the reaction can shift to favor either the products or reactants and the value of K also dictates whether or not a reaction is product favored (large K) or reactant favored (small K)

Anish Natarajan 4G

If the system is doing work on the surroundings, like when the volume of something is expanding or heat is being released; but if something is being compressed or heat is being put in, then the surroundings are doing work on the system.

Anish Natarajan 4G

Technically it's all dependent on the value of R that you use, but in most cases you'll be given a value that incorporates Kelvin rather than Celsius

Anish Natarajan 4G

I believe it was mentioned in our discussion section that the ratios are going to be the same (although I could be wrong on this)

Anish Natarajan 4G

If the Gibbs Free Energy is negative--that is, if T*DeltaS is larger than Delta H or Delta H is negative--then the reaction will be spontaneous. The inclusion of T as a variable shows that as temperature increases, all reactions eventually become spontaneous

Anish Natarajan 4G

The change in internal energy is a summation of the enthalpy and the work done on the system so Delta U is Delta H +w

Anish Natarajan 4G

If I recall correctly there are two phase change options, one being the transition from solid to liquid and the other one being from liquid to gas. The entropy change associated with the latter option is larger

Anish Natarajan 4G

In a reversible system what's happening is that heat is going into the system at basically the same rate that it's going out (think of it like if a balloon is slowly expanding vs just popping) and in an irreversible system you're going to get less work done and there will be a temperature change due...

Anish Natarajan 4G

In this particular case, since we're trying to talk about charge, n is the number of moles of electrons

Anish Natarajan 4G

Basically the thing that is getting reduced is acting as an oxidizing agent since the other element/molecule is getting oxidized (and vice versa)

Anish Natarajan 4G

The charge in this case will be 0 since Oxygen in this form is in a diatomic molecule.

Anish Natarajan 4G

If a reaction has an increase in entropy or a decrease in enthalpy, then it is more likely to be spontaneous. To compute the actual value you need to check if the Gibbs free energy of a reaction is negative and to do that you use the equation delta G=deltaH-T*deltaS

Anish Natarajan 4G

Both work but I'd be careful to convert all your units to the same scale (either joules or kilojoules) because the equations we use for entropy give us the answer in joules whereas the equations we use to calculate enthalpy frequently use kilojoules

Anish Natarajan 4G

It primarily depends on the units used; as a general rule 0.08206 works when you're using ideal gas law and 8.314 works for calculating deltaS since it does the conversion from L atm to joules for you

Anish Natarajan 4G

The first equation is used when the reaction is not at equilibrium and there is some reaction quotient Q that is not equal to K whereas the second reaction assumes that the reaction has reached equilibrium and Q=K.

Anish Natarajan 4G

In isothermal expansion, there is no work being done since the volume is expanding in extremely small increments to the point where delta V starts to approach 0; if there is no work being done and we know that the change in the internal energy of the system is 0 since it is isothermal, then we can s...

Anish Natarajan 4G

Gibbs Free Energy is basically a measure of the energy available to do work. In a more practical sense, if the delta G is negative, then there will be more energy available to do work instead of being contained within the chemical bonds of the product as potential energy; these types of reactions ar...

Anish Natarajan 4G

Although there isn't going to be a change in entropy/enthalpy, there is going to be a change in temperature that will alter the reaction constant K.

Anish Natarajan 4G

Not necessarily; if the absolute value of the change in enthalpy is less than the absolute value of the change in entropy then delta G will be negative and the reaction will be spontaneous. Theoretically you could actually be decreasing entropy and still getting a spontaneous reaction as long as del...

Anish Natarajan 4G

The Gibbs free energy of a reaction is not dependent on the path the reaction takes but rather, the net change between the internal energy of the products vs the internal energy of a reactant, making it a state function

Anish Natarajan 4G

There will always be some internal energy due to the movement of molecules in a system; however the change in internal energy will be 0

Anish Natarajan 4G

Enthalpy changes are dependent on changes in temperature, so if the change in temperature is 0, then then delta H=0

Anish Natarajan 4G

When work is done on a system, the sign is positive; when work is done by a system, the sign is negative

Anish Natarajan 4G

a cup of coffee is an open system in that the external temperature of the surroundings can affect the internal temperature of a system. A hot cup of coffee that exists in an area where the surrounding temperature is colder will allow for the heat transfer from the system to the surroundings.

Anish Natarajan 4G

A bomb calorimeter is a closed system, which means that there is no net change in volume. Since there is no change in volume there isn't any work being done and the change in internal energy (delta U) should be equal to q

Anish Natarajan 4G

You're going from a state of lower energy to a state of higher energy when you go from a solid to a liquid (or a liquid to a gas) so the change in enthalpy should be positive

Anish Natarajan 4G

I believe it is the number of elements within a system raised to the power of possible system states (i.e. if you have 3 molecules which can occupy 4 chambers then you have 3^4 possible states)

Anish Natarajan 4G

Spontaneous reactions depend on whether or not the delta G is negative; since the equation for delta G is
deltaH-T(deltaS), then if the enthalpy is positive you can still have a negative delta G (and a spontaneous reaction) if the absolute value of T(deltaS) is greater than the enthalpy change

Anish Natarajan 4G

If they use the term "isobaric" in the problem it means that the pressure is staying constant

Anish Natarajan 4G

It's an endergonic reaction since the reactants have less energy

Anish Natarajan 4G

There are different values for R depending on the units that you are using in your calculations

Anish Natarajan 4G

You probably shouldn't be getting a negative seeing as how the Acid/Base on the product side becomes a negative term when you set the entire equation equal to 0. Remember that it's b^2-4ac so the two negatives should cancel out

Anish Natarajan 4G

Increasing the concentration of the reactant will decrease Q, meaning that the reaction will shift towards the products in order to increase Q so that it can become = to K and vice versa

Anish Natarajan 4G

Generally if you're given a Ka/Kb value in a problem it's most likely a weak acid/base but just as a general rule of thumb it has to do with the electronegativity difference

Anish Natarajan 4G

Temperature changes K

Anish Natarajan 4G

More V/Less P=shift to side with more mols and vice versa

Anish Natarajan 4G

If you have a small percentage of the initial then that means that the change is negligible so if you have something in the denominator like .01-(8*10^-9) that's pretty much the same thing as .01

Anish Natarajan 4G

Can someone reiterate how water as a gas has more energy as water as a liquid when they are booth at 100 degrees C?

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