CHEMISTRY COMMUNITY

Nickolas Manipud 1C

I'm guessing they gave us cell potential to plug into our function and check our answer.

Nickolas Manipud 1C

For those questions, you don't have to worry about the order. Just write the reactants into the rate law.

Nickolas Manipud 1C

You use J/mol.

Look at the Arrhenius equation, k = A*e^(-Ea/RT). R has units of J*K-1*mol-1 while T has units of K. The K will cancel out so what you have left is J*mol-1. You want to cancel both of these out which can be done with Ea with units of J*mol-1.

Nickolas Manipud 1C

The book says that 2H+ + 2e- ---> H2 has a standard cell potential of "0, by definition." Why is this so?

Nickolas Manipud 1C

How can OH- be a part of the rate law if it is an intermediate?

Nickolas Manipud 1C

How do we know that ii) at high sucrose concentration is first order?

Nickolas Manipud 1C

Is there any relation between the pseudo-constant k' and the reverse rate constant k' ?

Nickolas Manipud 1C

The above poster is right. It's a shortcut but you can still use the 1st order integrated rate law to solve the problem.

Nickolas Manipud 1C

It's a good idea to know the derivations so you know where these equations come from which will give you a better understanding of the concepts.

Nickolas Manipud 1C

It might have been because the question gives you minutes. You're right to say that it is usually standard to use seconds. On the test, I'm sure that you'll still get credit if you use either seconds or minutes unless the question wants a specfic unit.

Nickolas Manipud 1C

You include it when a half-cell does not have any other solid or liquid that is part of the half-reaction to conduct electricity.

Nickolas Manipud 1C

The delta G is the maximum cell potential (the potential before we connect the electrical current). When we connect the current, the delta G of the cell gets closer and closer to zero over time since the cell is going towards equilibrium. Therefore, since delta G and E are directly related, E will g...

Nickolas Manipud 1C

I'm sure he'll give us the molecular formulas on the test

Nickolas Manipud 1C

I'm pretty sure you only put a comman if they are both aqueous and therefore in the same solution

Nickolas Manipud 1C

For these equations, $\Delta S=nCln(T2/T1), \Delta S=nRln(V2/V1)$ , why is there a C for one equation and an R for the other

Nickolas Manipud 1C

You usually want entropy to be in J/K so you would use molar heat capacity

Nickolas Manipud 1C

Standard enthalpy is the change in enthalpy for one mole under the conditions of 1 atm and 298 K.

Nickolas Manipud 1C

You can think of a process being spontaneous as the same as it being favorable. A process will naturally go in the direction that is favorable. In other words, it goes in the direction that increases entropy of the universe (this is true because of the 2nd law of thermodynamics).

Nickolas Manipud 1C

No, W does not have any units.

Nickolas Manipud 1C

Molecules want to achieve a low energy state so they do this by releasing energy through the formation of bonds

Nickolas Manipud 1C

The oxidation number is the charge of an atom or molecule.

If it loses, for example, three electrons, the oxidation number becomes 3+. If it gains 3 electrons, the oxidation number becomes 3-.

Nickolas Manipud 1C

The 2nd law states that the entropy of the universe is always increasing

Nickolas Manipud 1C

Because you just found the standard enthaply or molar entropy of 1 mole of some substance from the chemical reaction

Nickolas Manipud 1C

Some problems from the homework required using 8.206 x 10^-2

Nickolas Manipud 1C

No. Free expansion occurs since there is no external pressure acting upon the system.

Nickolas Manipud 1C

Wassup Janine You want to find how long it takes for ice to melt. The question says ice takes 10.5 h to reach 5 degrees Celsius and that the water at a liquid state at 0 degrees Celsius takes 0.5 h to reach 5 degrees Celsius. Therefore, the remaining 10.0 h must be from the ice melting. (10.5 - 0.5 ...

Nickolas Manipud 1C

The limiting reactant determines the amount of energy released by the reaction which will help us determine the final temperature

Nickolas Manipud 1C

You would use the enthalpies of formation for Zn+, Cl-, Zn (solid), and H+

Nickolas Manipud 1C

Nope! This was taken from his website: "Test 1 covers only Chapter 8 material covered in Weeks 1 and 2. Week 3 I will cover equation 4 (page 266) in Chapter 8. Therefore, no questions on isothermal, reversible expansion on Test 1. Concept questions involving work and internal energy will be on ...

Nickolas Manipud 1C

Doing ALL the problems (except for the ones he said to skip) he assigns will prepare you enough for the test

Nickolas Manipud 1C

Molar = J/(mol*K)
Specific = J/(g*K)
Essentially, use molar heat capacity when dealing with moles and specific heat capacity when dealing with grams.

Nickolas Manipud 1C

Depends on how much stuff we cover by Friday

Nickolas Manipud 1C

Work is done ON a system when the system's internal energy increases. This makes sense if you think about a system being compressed (which is work being done ON the system). Since it's being compressed, more pressure is created, leading to more internal energy in that system.

Nickolas Manipud 1C

You can use Dr. Lavelle's analogy of a person climbing a mountain. The change in altitude is a state function but the actual distance traveled is not a state function because it depends on what path the person takes (the climber could have taken a shortcut or a longer, more scenic route). The change...

Nickolas Manipud 1C

Rachel Formaker 1C wrote:Diaquadifluoromercury(I)

Wouldn't mercury have a charge of 3+ and not 1+?

Nickolas Manipud 1C

What's the name for [HgF2(OH2)2]+ ?

Nickolas Manipud 1C

Clarisse Wikstrom 1F wrote:What do you mean by "ratios of the change in equilibrium"?

When you draw the ICE box, in the "Change" row, you would get 10, 5, and 10 for A, B, and C, respectively. The ratios of 10, 5, and 10 are 2:1:2 which tells you the number of moles for A:B:C.

Nickolas Manipud 1C

The following plot shows how the partial pressures of reactant and products vary with time for the decomposition of compound A into compounds B and C. All three compounds are gases. Use this plot to do the following: (a) Write a balanced chemical equation for the reaction. (b) Calculate the equilibr...

Nickolas Manipud 1C

Dissociation of a diatomic molecule, X2(g) -> 2 X(g) occurs at 500 K. Picture 1 shows the equilibrium state of the dissociation and picture 2 shows the equilibrium state in the same container after a change has occurred. Which of the following changes will produce the change shown? (c) Decreasing th...

Nickolas Manipud 1C

For the reaction pcl5 \rightleftharpoons pcl3 + cl2 , Kc = 1.1 x 10^-2 at 400 K. (a) Given that 1.0 g of PCl5 is placed in a 250.-mL reaction vessel, determine the molar concentrations in the mixture at equilibrium. (b) What percentage of the PCl5 has decomposed at equilibrium at 400. K? I tried usi...

Nickolas Manipud 1C

clararehmann1B wrote:Notice that you can see which molecules have decayed within the flask. Start with counting out how many molecules have split apart!

The answer is flask 3 but I counted the the number of molecules that have split apart and there are 12 of these in both flasks 3 and 4. So why is flask 3 the answer?

Nickolas Manipud 1C

Do we have to know any other specific bond angles beside 90, 120, 180, and 109.5? For example, should we know that a trigonal pyramidal molecule has bond angles of 107 degrees or just that it is less than 109.5?

Nickolas Manipud 1C

Emma Li 3F wrote:How do you tell if a molecule (with 4 atoms) has a trigonal planar shape or is t-shaped?

I was having trouble with this too but this picture really helps
https://goo.gl/images/2yK9vp

Nickolas Manipud 1C

Essly Mendoza 1J wrote:Do you guys know what the average on the midterm was? Thanks!

Lavelle said 83%

Nickolas Manipud 1C

Remember you're only counting the REGIONS of electron density so single, double, and triple bonds are all considered as one region of electron density

Nickolas Manipud 1C

Mine is up but I wouldn't worry about it. It should be up eventually

Nickolas Manipud 1C

You would count the total number of electrons in the s-, p-, d-, and f- subshells which is 32 electrons. Then, since the question is only asking for electrons with ms = +1/2, you would divide 32 in half to get your answer of 16 electrons.

Nickolas Manipud 1C

I know that elements in s- and d-orbitals can become cations so therefore, their electrons tend to be given away. Meanwhile, in p-orbitals, the elements can become anions so they want to keep their electrons and pull in more electrons from a cation to create a stable valence shell.

Nickolas Manipud 1C

Remember that l = (n-1) so if n=7, then the possible l values are 0,1,2,3,4,5,6

Nickolas Manipud 1C

Can anyone explain to me why Cl has a higher electron affinity than Br? In general, electron affinity decreases as you go down a group because there are more shells between the nucleus and the valence electrons. As a result, the nuclear charge has less of an effect in pulling the valence electrons ...

Nickolas Manipud 1C

Question: In the heavier transition-metal elements, especially the lanthanoids and actinoids, there are numerous exceptions to the regular order of orbital occupation predicted by the buildingup principle. Suggest why more exceptions would be noted for these elements. Answer from Solutions Manual: ...

Nickolas Manipud 1C

Why does carbon have a higher electron affinity than nitrogen when the general trend is that electron affinity increases to the right?

Nickolas Manipud 1C

What is a radial node and how would you determine the number of radial nodes for orbitals?

Nickolas Manipud 1C

You should know that visible light is about 400-700 nm.

It also may be useful to know the order of the EM spectrum and that the Balmer series consists of visible light and Lyman consists of UV.

Nickolas Manipud 1C

Write the equation that allows one to calculate the electronic energy levels for the hydrogen atom. Do the calculated energies compare favorably with empirical observation (spectroscopic results)?

What does the second part mean?

Nickolas Manipud 1C

On Lavelle's website, you'll find a link that says "Constants and Equations." I feel like the ones in there will be given on the test.

Nickolas Manipud 1C

They're not really interchangeable terms.

I like to think of photons as "packets" of light. Photons carry an energy that determines how fast they move. This is important because the photon's speed (aka their frequency) can help us find that photon's wavelength and energy.

Nickolas Manipud 1C

It is possible for the electron to continue to move to higher levels. More often than not, the electron will drop back down to the ground state because it is most stable there. However, if an electron jumps to the first state, it can jump to the second state if the electron absorbs another photon ju...

Nickolas Manipud 1C

I don't round my sig figs until the very end to prevent my answer from going too far off from the correct answer.

Nickolas Manipud 1C

You multiply it by 11 O atoms because that is how many O atoms are in magnesium sulfate heptahydrate (MgSO4 * 7H20)

Multiplying it by 11 will give you moles of O which you then multiply by Avagadro's constant (6.022 * 10^23) to get the number of O atoms.

Hope this helped!

Search found 60 matches