CHEMISTRY COMMUNITY

chrisavalos-2L

I was wondering how to determine which element to add to the cell diagram if there is no conducting agent, is it always Platinum, or do we need to know different ones for different instances?

chrisavalos-2L

The easiest way to determine n is to take the 2 half reactions and balance them normally and then balance them with their charges. This means to add a number of electrons to the side that contains the more positive value, and then after this, you need to assure that this value of electrons is equal ...

chrisavalos-2L

This equation is w==P deltaV, this is used when you have a constant pressure and are asked to find the work that the system performed and will be given the two values for the different volumes.

chrisavalos-2L

I was wondering how it is possible to determine if a reaction is zero order... I thought that we could do this by seeing how the concentration of each reactant affects the over rate but I do not know how to go about determining this?

chrisavalos-2L

I was wondering what the significance of the slow step and the fast step in reactions, and how they help us in relation to chemical kinetics?

chrisavalos-2L

I was wondering how to determine the overall order of a reaction? I remember my TA saying that the sum of the reactions powers is the overall order... but how do we determine is it is zero, first or second order from this?

chrisavalos-2L

This means that Cu2+ has a greater ability as an oxidizing agent, and therefore it can be very easily reduced.

chrisavalos-2L

You do not include a liquid in the cell diagram such as H20 but you do include H+ because it is an aqueous solution.

chrisavalos-2L

I think that we care about the kinetics in a reaction because we are hoping to understand, like you said, how different variables affect the reaction rate, so we are probably going to be analyzing the effects in the change of the variable and how this changes the overall rate and how this would affe...

chrisavalos-2L

chrisavalos-2L wrote:This equation for change in entropy is used when it is a reversible reaction.

--- Also when there is no change in temperature (constant temperature)

chrisavalos-2L

This equation for change in entropy is used when it is a reversible reaction.

chrisavalos-2L

The residual entropy is the entropy that remains in a substance at 0 degrees Kelvin, this would usually be calculated for a perfect crystal.

chrisavalos-2L

In the reaction, an oxidating agent is the one that becomes reduced during the course of the reaction, and the reducing agent is the one that become oxidized in the reaction.

chrisavalos-2L

There would be no change because there will be no interactions with the surroundings, therefore no energy lost or energy gained so delta U will be zero, and the U itself will be the same.

chrisavalos-2L

A bomb calorimeter is an isolated system because it prevents energy and matter from interacting with the surroundings of the system, hence the definition of an isolated system.

chrisavalos-2L

S is equal to zero when there is temperature is at zero Kelvin and when there is no disorder, in the instance of a perfect crystal.

chrisavalos-2L

Any constant numbers, for example, Avogadro's number, the gas constant or Boltzmann's constant(etc.) will be given to us on the equation sheet that we get before each test, so you do not technically need to memorize them. Although once we have used them enough you probably will.

chrisavalos-2L

I would say no, because with past topics that we have been tested on Professor Lavelle always either integrated the concept into the lectures or the notes, therefore since this has not been in either, I do not think that we will be tested on it

chrisavalos-2L

"U" is the variable that represents the actual internal energy of a system. While "△U" represents the change in the internal energy of a system.

chrisavalos-2L

I was wondering how to know which of the different work equations that we are to use for different situations?

chrisavalos-2L

An isolated system is when the system can neither transfer matter or energy into its surroundings, so this would be a system that is completely sealed and insulated from its surroundings. A closed system is when there can be a transfer of energy however not a transfer of matter, therefore this would...

chrisavalos-2L

There is a negative sign because this indicates that the system in question is performing work, therefore it is releasing energy; hence the negative sign.

chrisavalos-2L

Essentially they are the same equation you would just use one or the other depending on the information that is given in the problem.

chrisavalos-2L

Steam causing more of a burn than water because in the vapor phase the water must release more energy quickly in de-vaporizing and then still has to transfer the energy to the skin which is sufficiently more than that of boiling water

chrisavalos-2L

This means that rather than being unconcerned with the way that the final product was created and with state functions like enthalpy, however with a nonstate function the process to achieve it actually matters in the calculations.

chrisavalos-2L

Professor Lavelle mentioned to us that we should assume that the temperature of reactions would be 25 degrees Celsius unless stated otherwise.

chrisavalos-2L

A positive delta H indicates that the reaction is endothermic and that the reaction takes in heat/energy to occur and if it is negative that means that the reaction is exothermic and releases heat and energy.

chrisavalos-2L

Yes, when Q<K the forward reaction is favored and therefore in order to reach equilibrium as all reactions attempt in the long run, there will be more products formed to eventually reach equilibrium.

chrisavalos-2L

An easy way that professor Lavelle gave us to help identify weak acids is that they have a Ka that is less than that of 10^-3.

chrisavalos-2L

Ka is used when dealing with a chemical reaction that includes an acid and Kb is used when there is a chemical reaction that includes a base. Kc is the equilibrium constant of concentrations.

chrisavalos-2L

No, it doe not affect the equilibrium constant K, this is because the constant is not determined by the concentration of the reactants and products but rather the rate at which the reaction or the reverse reaction occurs.

chrisavalos-2L

I was wondering why the temperature changes the equilibrium constant? Is there a way to calculate this or is this just a fact that we need to know and the calculation will be given to us?

chrisavalos-2L

I was a little confused on exactly what the reaction quotient is. So it is calculated the same way that K is, but why is it considered a separate entity?

chrisavalos-2L

I believe that since we covered the naming of coordination compounds in class we will be tested on it

And also I think that it would be a good idea to know the formula for en as if we are given a coordination complex to name it might have the formula in it rather than the abbreviation en.

chrisavalos-2L

Am I understanding this right...

Once an acid donates a proton (hydrogen) the resulting molecule is the conjugate base of that acid and vice versa for a base and a conjugate acid?

chrisavalos-2L

I was wondering what the difference was between amphoteric and amphiprotic?

chrisavalos-2L

Degeneracy corresponds with the orbitals, therefore; they go as follows, s=1, p=3, d=5, f=7.

chrisavalos-2L

I was wondering what the trend for electronegativity was, is it the same as ionization energy?

chrisavalos-2L

Elements that are in period three can have what is called an expanded octet in that they can go beyond the octet rule and have greater than it.

chrisavalos-2L

This is because a sigma bond is the overlapping of the s orbital and since there is only one there can only be one sigma bond. Also, there can be multiple pi bonds because it occurs between p orbitals, and there are three therefore there can be multiple pi bonds

chrisavalos-2L

A way that you determine whether or not a molecule is polar from looking at the Lewis structure is determining the dipole moments (if there are any), and if it does have dipole moments that do not cancel out then the molecule is polar.

chrisavalos-2L

b) In a Fluorine atom with 5 valence electrons in the 2p orbital, what is the probability of finding an electron in the exact center of this orbital?

I was wondering how to determine this probability?

chrisavalos-2L

I was wondering how to determine when a dipole moment occurs and what exactly a dipole moment is?

chrisavalos-2L

I was wondering how to determine the difference between ionic and covalent bonds?

chrisavalos-2L

I was wondering if there was an easy short way in determining the shape of a molecule based on its molecular formula without drawing the Lewis structure first? Or is the Lewis structure necessary for determining the shape?

chrisavalos-2L

What is the rule for a combustion equation? Do they always produce Carbon Dioxide and Water? I have just never been sure of this. Thank You.

chrisavalos-2L

I was wondering if there was any way to calculate actual yield or does it need to be given to us?

chrisavalos-2L

I was a little confused in lecture today when we were talking about the tetrahedral shape, so just to clarify, because there are 3 dimensions that we are looking at the tetrahedral shape takes advantage of these 3 dimensions and this is what cause the shape? Also when drawing this structure is it ne...

chrisavalos-2L

I was wondering if the question asks to balance the combustion equation for a specific element how are we to know what will be produced by the combustion equation, is it always the same?

chrisavalos-2L

I was wondering how to find the amount of electrons in an atom when given the two quantum numbers n and l.

For example if the question was : how many electrons are in an atom with the following two quantum numbers, n= 3 and l= 2?

How would I go about determining this?

chrisavalos-2L

So, I know that the trend in the periodic table for the atomic radius is that it increases down a group and decreases from left to right across a period. I was wondering what the explanation for this is, that is what is the reason for this trend?

chrisavalos-2L

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6x10^3 km/s (a) What is the wavelength of the ejected electron? I was wondering how I would set up this equation without the mass of an electron? I was also wondering if I would need to change the units from km/s in...

chrisavalos-2L

Question: If the uncertainty in the momentum increases for a given particle what does this mean for the uncertainty in its wavelength?

I was wondering what the relationship between these two uncertainties are and how one can potentially affect the other?

chrisavalos-2L

How many orbitals can have the following quantum numbers in an atom? (a) n=2, l=1 I was wondering how I would answer this question? I know that there are 3 orbitals because it is in the 2p sub shell, but does that mean that that is the highest number of orbitals that it can have or does the n=2 have...

chrisavalos-2L

(b)When an electron beam strikes a block of copper, x-rays with a frequency of 2 x 10^18 Hz are emitted. What is the wavelength of these rays in picometers?

I was wondering what equation/ process would be used to solve this equation? Would it be the work function? Thank You

chrisavalos-2L

(a) How many values of the quantum number l are possible when n=7?

I was wondering if there is an equation that we have to use to find this number or is there are set of values that we should know?

chrisavalos-2L

Which of the following increase when an electron in a lithium atom undergoes a transition from the 1s-orbital to a 2p-orbital? (a) Energy of the electron (b) value of n (c) value of l (d) radius of the atom - I think that the answer to this question is (d), because moving to this orbital would incre...

chrisavalos-2L

If 3.61x10^-19 J is required to remove an electron with the kinetic energy from a metal surface, what would be the longest wavelength light that could do this?

I was wondering how to set up the problem initially, I know the concept of what we are looking for but I'm not sure on the initial set up?

chrisavalos-2L

I was wondering if we are given an instance where we have the mass of an electron but not the velocity and are asked to find the threshold energy, is there a way to calculate the velocity in this instance or would they have to give us the velocity in this situation?

chrisavalos-2L

Which of the following happens when the frequency of electromagnetic radiation decreases? Explain your reasoning (a) the speed of radiation decreases (b)the wavelength of radiation decreases (c)the extent of the change in the electrical field at a given point decreases (d)the energy of the radiation...

chrisavalos-2L

I was wondering if the question gave us the initial volume in mL and asked us to solve for the final volume would we give the answer in L or mL, or does it matter?

chrisavalos-2L

I was wondering when balancing a chemical equation if you need to put the state of matter? Also I was wondering what the best technique is to begin balancing any equation?

chrisavalos-2L

A student prepared a solution of sodium carbonate by adding 2.111g of the solid to a 250 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 Na + ; (b) 4.98 mmol C...

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