CHEMISTRY COMMUNITY

Celeste 1I

How many grams of formic acid, HCOOH, do you need to prepare 1.00L of a pH 3.26 solution? Ka of formic acid=1.8x10^-4. The only thing I get is that the hydronium concentration is 5.5x10^-4 and thats about it.

Celeste 1I

What does “first” “second” or “zero” order even mean? And how can you tell the difference?

Celeste 1I

Does the order other than anode, cathode matter in cell diagrams? Such as the state or something?

Celeste 1I

For some of the answers in the book they add Platinum to the cell diagram, or is already in the diagram and seems random to me. Why do they sometimes add Pt?

Celeste 1I

how do you know which half reaction to flip when the electrons are on the same side for both half reactions?

Celeste 1I

What exactly is a half reaction? and why do we use that instead of the whole reaction?

Celeste 1I

Oil Rig, oxidize is loss reduction is gain

Celeste 1I

The degree symbol means standard.

Celeste 1I

2SO2(g)+O2(g)->2SO3(g) at 25 degrees Celsius and 1 atm in a constant pressure cylinder. I got a) initial volume =1.7L b) limiting reagent is SO2 c)final volume is 1.1L d) -40J of work is done on the system. Im confused on e) How much enthalpy is exchanged and does it leave or enter the system? How d...

Celeste 1I

Calculate the work that must be done against the atmosphere for the expansion of the gaseous products in the combustion of 1.00 mol C6H6(l) at 25 C and 1.00 bar. (b) Using data in Appendix 2A, calculate the standard enthalpy of the reaction. (c) calculate the change in internal energy of the system ...

Celeste 1I

oops didn't know there were different forms. The question asks for the pH of a .030M solution of sodium sorbate(C6H7O2), given that the pKa of sorbic acid(C6H8O2) is 4.74. The reaction is: C6H7O2+H2O<=>C6H8O2+OH

Celeste 1I

Can anyone tell me the correct answer for this question. I got it wrong initially and want to know if I've done it correctly this time. Thanks!

Celeste 1I

Use the one that is easiest to use, I'm assuming. If they give you grams then use m and if they give you mols use n. Just make sure to then use the corresponding C. Write out your units to ensure you're getting the right answer and everything cancels out.

Celeste 1I

Because of the second law of thermodynamics, entropy can never decrease, so when a system reaches equilibrium that means that entropy has maxed out, and it can't increase either because every state has been reached.Hope that makes sense.

Celeste 1I

As far as I know, I don't think so. I don't think being able to produce the equations really tests our knowledge about Hess's law. Hopefully not.

Celeste 1I

I'm assuming you mean constant pressure. If something is under constant pressure that means the change in pressure is equal to 0 which means you can basically ignore it in the equation.

Celeste 1I

We usually don't have to derive equations but there are usually conceptual questions about the equations.

Celeste 1I

If it is not otherwise stated, yes you assume the pressure is equal to 1 atm.

Celeste 1I

A careless laboratory technician wants to prepare 200mL of a 0.025M HCL solution, but uses a 250.0mL volumetric flask instead. a) What is the pH of the desired solution?b) what is the actual pH? I guess I'm confused on how to start this.

Celeste 1I

K tells us the equilibrium constant and Q is the ratio of the concentration of products and reactants at any given time. You can use K to find whether a reaction is in equilibrium and which side it it more likely to favor. If Q is less than K then the reaction will shift right and if Q is greater th...

Celeste 1I

It would be on both sides of the equation and would just cancel out in the equilibrium equation. So it doesn't effect K.

Celeste 1I

It will cover everything up to Friday's lecture.

Celeste 1I

for part c) it asks "assuming that the initial pressure of X2 was 0.10 bar, calculate the value of K for the decomposition." the only other information given is that the reaction is a dissociation of a diatomic molecule, X2 over time and that it reaches equilibrium after 54.5% of molecules...

Celeste 1I

Think of it this way, if Kc is a constant and say is equal to 1 in R<->P and one mol of reactant is used then inly one mol of product will be formed in order to reach that ratio, however if 5 mols of reactant are used then 5 mols of product must be made to be at equilibrium. hope that makes sense.

Celeste 1I

Just as a note Kp can only be used when talking about gases. Not sure if that helps. The partial pressure or concentration can be used depending on which is given.

Celeste 1I

How do you know which Lewis Structure to use for telling polarity when the arrangement of atoms can either cause the atom to be polar or non polar depending on where you put them? (cis or trans)

Celeste 1I

Why is the shape of ICl3 t-shaped with the two lone pairs at the top? Why don't the lone pairs separate as far as they can from each other at the top and bottom like in IF4, the lone pairs are in complete opposite sides of the central atom?

Celeste 1I

How do you use polarizability and polarizing power to determine which molecule has a higher covalent character. Like between CaS and CaO?

Celeste 1I

He said we won't have to know exact angles just that they are less than what they would be without lone pairs.

Celeste 1I

I think the bent shape comes from a third region of electron density being a lone pair. So the lone pair pushes the other two atoms down.

Celeste 1I

its because oxygen has two lone pairs which repel each other and the atoms more than atom to atom repulsion causing a bent shape. So because the lone pairs repel the Hydrogen atoms more than each one to one other their angle becomes slightly less than 109.5.

Celeste 1I

I think the shape of ch2cl2 is tetrahedral. So the chlorine atoms are 109.5 degrees away from each other and not opposite from each other. This means theres a dipole moment which don't cancel. Hope this helped.

Celeste 1I

I think whenever theres a lone pair, it repels the other atoms away more than the repulsion between atoms. So, if there is a lone pair it will bring the two atoms closer together making it slightly less than a normal bent angle. Hope that answered your question.

Celeste 1I

The formal charge for the one with a double bond and one single bond, the O on the right is the only one with a formal charge of 0. The one on the left has a formal charge of -1 and S has a fc of +1. When both bonds are double bonds the formal charge of all three change to 0 which mean that is the m...

Celeste 1I

Just have a question about how we receive points for chemistry community. if I forget one week, can I make up points by posting more in the following week?

Celeste 1I

I like to think of it as how many "open" spaces the atoms have. For example, when choosing what the central atom in CO2 is, C has 4 open spaces while O has 2 to fill the shells. So, it would make sense to choose C since it has more open spaces. Hope this helps!

Celeste 1I

A line is used to show a chemical bond, or that two atoms are "sharing" electrons. Putting two dots in between two atoms that are sharing it would mean the same thing. However, when showing the lewis structure of just one atom, using a line wouldn't really make sense since its not bound to...

Celeste 1I

I believe this is because cations are positively charges and, therefore, would repel each other if put next to each other.

Celeste 1I

I think he said basically anything you can see with the naked eye does not have a detectable wavelength. anything like an electron will have a detectable wavelength. I dont think he'll ever ask if something is detectable since there is no exact number.

Celeste 1I

I suggest just keeping track of the grades you get on homework and participation and tests and exams will most likely get posted into myUCLA. At the end of the quarter check to make sure all your grades are imputed, so make sure not to throw any assignments away since TAs occasionally make mistakes....

Celeste 1I

I think they are normally in nm when speaking about the visible light spectrum since the wavelengths are so small. you can also leave it in m as long as you use the correct notation nm = 10^-9 m. it means the same thing.

Celeste 1I

Its asking you to find the percent composition of each element, I think. If you assume you have 100g of L-carnitine then it makes it pretty easy to find the percentage.

Celeste 1I

I thought it might of been because of conservation of mass. We can't create nor destroy mass so adding it would be like creating mass?

Celeste 1I

Question h.1 asks why you can't just add an extra O molecule to balance the equation? Why wouldn't we be able to do that?

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