## Search found 44 matches

Sat Mar 16, 2019 9:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Acid and Base Equilibrium
Replies: 1
Views: 228

### Acid and Base Equilibrium

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.
Wed Mar 06, 2019 11:31 am
Forum: Zero Order Reactions
Topic: General “order” question
Replies: 6
Views: 454

### General “order” question

What does “first” “second” or “zero” order even mean? And how can you tell the difference?
Sun Mar 03, 2019 10:58 pm
Forum: Balancing Redox Reactions
Topic: Order in Cell diagrams
Replies: 3
Views: 172

### Order in Cell diagrams

Does the order other than anode, cathode matter in cell diagrams? Such as the state or something?
Sun Mar 03, 2019 10:56 pm
Forum: Balancing Redox Reactions
Topic: Cell diagrams
Replies: 8
Views: 269

### Cell diagrams

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?
Sun Mar 03, 2019 10:54 pm
Forum: Balancing Redox Reactions
Topic: Ecell
Replies: 4
Views: 170

### Ecell

how do you know which half reaction to flip when the electrons are on the same side for both half reactions?
Sun Feb 24, 2019 9:48 pm
Forum: Balancing Redox Reactions
Topic: Half Reaction
Replies: 2
Views: 99

### Half Reaction

What exactly is a half reaction? and why do we use that instead of the whole reaction?
Sun Feb 24, 2019 9:36 pm
Forum: Balancing Redox Reactions
Topic: Mnemonic for Redox
Replies: 5
Views: 283

### Re: Mnemonic for Redox

Oil Rig, oxidize is loss reduction is gain
Sun Feb 24, 2019 9:30 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Meaning of E
Replies: 3
Views: 254

### Re: Meaning of E

The degree symbol means standard.
Wed Feb 13, 2019 4:30 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 6th ed 8.101
Replies: 1
Views: 124

### 6th ed 8.101

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...
Wed Feb 13, 2019 2:54 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 6th edition 8.93
Replies: 1
Views: 120

### 6th edition 8.93

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 ...
Tue Feb 12, 2019 11:10 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Quiz 1 #5
Replies: 7
Views: 458

### Re: Quiz 1 #5

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
Tue Feb 12, 2019 11:02 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Quiz 1 #5
Replies: 7
Views: 458

### Quiz 1 #5

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!
Sun Feb 10, 2019 11:12 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: q=mCdeltaT
Replies: 15
Views: 4295

### Re: q=mCdeltaT

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.
Sun Feb 10, 2019 11:09 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy at quilibrium
Replies: 2
Views: 150

### Re: Entropy at quilibrium

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.
Sun Feb 10, 2019 11:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 5
Views: 201

### Re: Hess's Law

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.
Sun Feb 03, 2019 11:28 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: RXN constant P
Replies: 2
Views: 146

### Re: RXN constant P

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.
Sun Feb 03, 2019 11:24 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: deriving the work equation: -P*deltaV
Replies: 2
Views: 96

### Re: deriving the work equation: -P*deltaV

We usually don't have to derive equations but there are usually conceptual questions about the equations.
Sun Feb 03, 2019 11:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Constant P
Replies: 4
Views: 157

### Re: Constant P

If it is not otherwise stated, yes you assume the pressure is equal to 1 atm.
Wed Jan 23, 2019 3:21 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 6th Edition 12.27
Replies: 2
Views: 376

### 6th Edition 12.27

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.
Sun Jan 20, 2019 8:20 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q and K
Replies: 10
Views: 398

### Re: Q and K

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...
Sun Jan 20, 2019 8:15 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Water in ICE tables
Replies: 10
Views: 631

### Re: Water in ICE tables

It would be on both sides of the equation and would just cancel out in the equilibrium equation. So it doesn't effect K.
Sun Jan 20, 2019 8:13 pm
Forum: Student Social/Study Group
Topic: test 1
Replies: 10
Views: 626

### Re: test 1

It will cover everything up to Friday's lecture.
Sun Jan 13, 2019 10:30 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: homework 11.7 6th edition [ENDORSED]
Replies: 1
Views: 148

### homework 11.7 6th edition[ENDORSED]

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...
Sun Jan 13, 2019 10:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: HW PROBELM 1 PART D
Replies: 4
Views: 186

### Re: HW PROBELM 1 PART D

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.
Sun Jan 13, 2019 10:04 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant
Replies: 6
Views: 225

### Re: Equilibrium constant

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.
Mon Nov 26, 2018 9:38 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar and Non-polar
Replies: 1
Views: 105

### Polar and Non-polar

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)
Mon Nov 26, 2018 2:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Lone Pairs
Replies: 1
Views: 58

### Lone Pairs

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?
Sun Nov 25, 2018 10:39 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: Covalent Character
Replies: 1
Views: 129

### Covalent Character

How do you use polarizability and polarizing power to determine which molecule has a higher covalent character. Like between CaS and CaO?
Sun Nov 25, 2018 10:35 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond angle
Replies: 3
Views: 123

### Re: Bond angle

He said we won't have to know exact angles just that they are less than what they would be without lone pairs.
Sun Nov 25, 2018 10:24 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: linear vs bent question
Replies: 7
Views: 313

### Re: linear vs bent question

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.
Sun Nov 18, 2018 10:03 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles for H2O
Replies: 8
Views: 4434

### Re: Bond Angles for H2O

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.
Sun Nov 18, 2018 9:54 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar/Nonpolar
Replies: 3
Views: 181

### Re: Polar/Nonpolar

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.
Sun Nov 18, 2018 9:52 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Bond Angles Between the Same shape
Replies: 6
Views: 264

### Re: Bond Angles Between the Same shape

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.
Mon Nov 05, 2018 11:59 am
Forum: Lewis Structures
Topic: SO2 Lewis Structure
Replies: 4
Views: 448

### Re: SO2 Lewis Structure

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...
Mon Nov 05, 2018 11:37 am
Forum: Administrative Questions and Class Announcements
Topic: Chemistry Community
Replies: 2
Views: 172

### Chemistry Community

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?
Sun Oct 28, 2018 10:01 pm
Forum: Ionic & Covalent Bonds
Topic: Lewis Dot Structures: Ionization Energy
Replies: 6
Views: 264

### Re: Lewis Dot Structures: Ionization Energy

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!
Sun Oct 28, 2018 9:56 pm
Forum: Lewis Structures
Topic: General Q on Lewis Structures
Replies: 2
Views: 84

### Re: General Q on Lewis Structures

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...
Sun Oct 28, 2018 9:53 pm
Forum: Lewis Structures
Topic: Lewis Structure for Compounds
Replies: 6
Views: 245

### Re: Lewis Structure for Compounds

I believe this is because cations are positively charges and, therefore, would repel each other if put next to each other.
Sun Oct 14, 2018 10:51 pm
Forum: DeBroglie Equation
Topic: Wavelength Verification in Lab
Replies: 2
Views: 53

### Re: Wavelength Verification in Lab

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.
Sun Oct 14, 2018 10:34 pm
Forum: Student Social/Study Group
Replies: 4
Views: 263

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....
Sun Oct 14, 2018 10:28 pm
Forum: Properties of Light
Topic: Units for Wavelength
Replies: 7
Views: 250

### Re: Units for Wavelength

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.
Thu Oct 04, 2018 9:48 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: F 5 Percent Composition
Replies: 4
Views: 148

### Re: F 5 Percent Composition

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.
Thu Oct 04, 2018 9:32 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Procedure
Replies: 7
Views: 379

### Re: Balancing Procedure

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?
Thu Oct 04, 2018 9:27 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Procedure
Replies: 7
Views: 379

### Balancing Procedure

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?