## Search found 38 matches

Sun Mar 18, 2018 1:01 am
Forum: Balancing Redox Reactions
Topic: Balancing for Acidic Conditions
Replies: 2
Views: 239

### Re: Balancing for Acidic Conditions

For acidic solutions, you balance O atoms by adding H2O and balance H atoms by adding H+. Since you added H2O atoms to the reactants side you had to add H+ to the other side to balance the H atoms you added
Sat Mar 17, 2018 10:15 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: 14.101
Replies: 4
Views: 611

### Re: 14.101

How come Q= 1/[K+]
Sat Mar 17, 2018 2:58 pm
Forum: General Rate Laws
Topic: 15.85
Replies: 3
Views: 410

### Re: 15.85

I am also confused. Also, does anyone know if we will have to write the proposed structures for the exam?
Sun Mar 11, 2018 9:29 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: 15.51? Molecularity?
Replies: 3
Views: 351

### Re: 15.51? Molecularity?

The rate law of any reaction is always given by the slow step. Therefore, because the second step is fast, you can ignore the second step.The Rate law for the formation of NOBr will then be Rate=k[NO][Br2] since the slow step says NO +Br2 -> NOBr2
Sun Mar 11, 2018 9:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.67?
Replies: 5
Views: 594

### Re: 15.67?

The solution from Chegg helped me FOR PART A) 15.67 The presence of a catalyst provides a reaction pathway in which the activation energy (Ea) of a certain reaction is reduced from 125kjmol^-1 to 75kjmol^-1 a) By what factor does the rate of the reaction increase at 298K, all other factors being equ...
Wed Mar 07, 2018 4:38 pm
Forum: First Order Reactions
Topic: First Order Integrated Rate Law
Replies: 3
Views: 247

### First Order Integrated Rate Law

When do I use kt=lnA./A
and when do I use kt=2.303logA./A
Mon Mar 05, 2018 5:44 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: 15.23?
Replies: 3
Views: 230

### Re: 15.23?

On chegg part of the solution is written :

[A] = [A]* - ([B]/2)
[A] = (0.153)- 2(0.034) = 0.085

Why is the first part written as ([B]/2) ?
Sun Mar 04, 2018 5:24 pm
Forum: First Order Reactions
Topic: Half-life of first order reactions [ENDORSED]
Replies: 4
Views: 319

### Re: Half-life of first order reactions[ENDORSED]

The half-life of a substance is the time needed for its concentration to fall one-half its initial value. It doesn't depend on concentration.
Sun Mar 04, 2018 5:18 pm
Forum: Zero Order Reactions
Topic: What role do coefficients play?
Replies: 3
Views: 219

### Re: What role do coefficients play?

Unique average rate depends on the coefficients used in the balanced equation.

For reaction aA =bB -> cC+ dD,
Unique average reaction rate= -(1/a) delta[A] / delta t = -(1/b) delta[B] / delta t = (1/c) delta[C] / delta t = (1/d) delta[D] / delta t
Sun Mar 04, 2018 5:15 pm
Forum: Zero Order Reactions
Topic: Real Life Example
Replies: 2
Views: 235

### Re: Real Life Example

Here, this helped me out: "Zero-order kinetics is always an artifact of the conditions under which the reaction is carried out. For this reason, reactions that follow zero-order kinetics are often referred to as pseudo-zero-order reactions. Clearly, a zero-order process cannot continue after a ...
Thu Feb 22, 2018 6:06 pm
Forum: Balancing Redox Reactions
Topic: 14.15
Replies: 1
Views: 201

### 14.15

Write the half reactions and devise a galvanic cell
a) AgBr (s) -> Ag+ (aq) +Br- (aq), solubility equilibrium

Why is the half reaction for reduction : Ag+(aq) + e- -> Ag (s)
Why can't it be AgBr (s) -> Br- (aq) ?
Thu Feb 22, 2018 3:05 pm
Forum: Balancing Redox Reactions
Topic: 14.13
Replies: 1
Views: 112

### 14.13

d) Au^(+) (aq) -> Au(s) + Au^(3+) (aq) Why can't I use Au+ (aq) -> Au^(3+) (aq) for the oxidation half reaction? When I used that I was able to get the correct overall balanced redox reaction. And when I got the cell diagram, couldn't I have placed Pt(s) on the anode side? The solutions don't have t...
Thu Feb 22, 2018 1:52 pm
Forum: Balancing Redox Reactions
Topic: 14.11
Replies: 3
Views: 251

### Re: 14.11

Someone correct me if I'm wrong but I think the reason why O2 and H+ are on the same side is because the reaction would not be oxidizing if it was either
H+ -> O2 or
O2 -> H+
The equation has to be H2O -> O2 + H+ because then the reaction will be oxidizing for H in H2O -> H+
Wed Feb 21, 2018 10:12 pm
Forum: Balancing Redox Reactions
Topic: 14.11
Replies: 3
Views: 251

### 14.11

14.11 Write the half reactions and the balanced equation for the cell reaction for each of the following galvanic cells: d) Pt(s) | O2 (g) | H+ (aq) || OH-(aq) | O2 (g) | Pt(s) I know that on the left of the || is anode and the right is cathode. Oxidation occurs at anode and reduction occurs at cath...
Wed Feb 21, 2018 7:17 pm
Forum: Balancing Redox Reactions
Topic: 14.5
Replies: 1
Views: 257

### 14.5

Br2(l)-> BrO3-(aq) + Br-(aq) I'm having a hard time finding numbers for H2O and OH- when balancing the Hydrogens. Does anyone have any tips/tricks?? I know that since it's basic, to balance the hydrogens I have to add H20 to the side that needs H, and then add OH- to the other side. So far I have ?O...
Wed Feb 21, 2018 6:29 pm
Forum: Balancing Redox Reactions
Topic: Acidic or basic?
Replies: 2
Views: 170

### Acidic or basic?

How do you determine if a reaction is acidic or basic? Can you tell just by looking at the reaction given?
Sun Feb 18, 2018 10:39 pm
Forum: Balancing Redox Reactions
Topic: Exercise 14.17
Replies: 6
Views: 327

### Re: Exercise 14.17

Please write the full problem too
Sun Feb 18, 2018 10:38 pm
Forum: Balancing Redox Reactions
Topic: 14.1
Replies: 5
Views: 255

### Re: 14.1

For part d, to determine the balanced equation, you multiply the oxidation half reaction by 3 and then add it with reduction half reaction. Oxidation: 3C2HxOH->3C2H4O + 6H +6e- Reduction: Cr2O7^(2-) +14H +6e- -> 2Cr^(3+) +7H2O The electrons cancel out. Balanced Redox Reaction: 3C2H5OH + Cr2O7^(2-) +...
Sun Feb 18, 2018 9:17 pm
Forum: Balancing Redox Reactions
Topic: H+ vs H2
Replies: 3
Views: 181

### H+ vs H2

Why do we use H+ to balance the hydrogens in a redox rxn instead of H2?
Tue Feb 13, 2018 1:36 pm
Forum: Van't Hoff Equation
Topic: Constants and formulas
Replies: 7
Views: 468

### Re: Constants and formulas

In class, Lavelle said that he won't ask us to derive anything for the exam, but it will still be helpful to know how.
Tue Feb 13, 2018 1:05 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: 9.101 (b) [ENDORSED]
Replies: 4
Views: 644

### Re: 9.101 (b)[ENDORSED]

Also from chegg, it states that entropy change depends on space for disorder, so since there is more space in the exterior there will be more disorder
Mon Feb 12, 2018 7:26 pm
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: 9.105
Replies: 1
Views: 248

### 9.105

9.105 states " The dissolution of carbon dioxide in red blood cells is catalyzed by the enzyme carbonic anhydrase: CO2(g) + H2O(l) -> H2CO3(aq) . Predict the sign of the entropy of reaction from a visual inspection of the equation and explain your reasoning." On Chegg, it says that one mol...
Tue Feb 06, 2018 12:24 pm
Forum: Student Social/Study Group
Topic: Monday 02/05 Lecture
Replies: 1
Views: 362

### Monday 02/05 Lecture

Hi, unfortunately I wasn't able to make Monday's lecture. Can someone tell me what topics were discussed on Monday so I can look up some videos to review it? Or if you could email me your notes that would be helpful too.
aprilfaeee@gmail.com
Mon Feb 05, 2018 5:07 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.17
Replies: 10
Views: 528

### Re: 11.17

I got -2.7kj/mol also. I think the solutions just had an error.
Sun Feb 04, 2018 10:26 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.77
Replies: 1
Views: 74

### 11.77

For 11.77 Predict whether each of the following equilibria will shift toward products or reactants with a temperature increase. a) N2O4 (g) (equilibrium arrows) 2NO2(g) , deltaH =+57 kj How am I supposed to predict this? From my notes I know that there will be a shift towards reactants if delta G is...
Sun Feb 04, 2018 10:08 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Difference between deltaG and deltaG*
Replies: 2
Views: 88

### Re: Difference between deltaG and deltaG*

Also, for homework/tests, if I forget to write naught in the equations/answers then will I miss points?
Sun Feb 04, 2018 10:05 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Difference between deltaG and deltaG*
Replies: 2
Views: 88

### Difference between deltaG and deltaG*

Can someone explain the difference between deltaG and deltaG* naught
Sat Feb 03, 2018 4:47 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.15 Gibbs Free Energy and Q
Replies: 1
Views: 147

### 11.15 Gibbs Free Energy and Q

11.15 (a) Calculate the reaction Gibbs free energy of I2(g) -> 2 I(g) at 1200. K (K=6.8) when the partial pressures of I2 and I are 0.13 bar and 0.98 bar, respectively.

I used deltaG* =-RTlnK
and then used
deltaG=deltaG*+RTlnQ

I'm not getting the correct answer though. How do I calculate Q?
Sun Jan 28, 2018 8:00 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: 8.49
Replies: 2
Views: 160

### 8.49

"Oxygen disulfide is a colorless, very poisonous gas that reacts rapidly with water vapor to produce O2, HF, and heat: OF2(g) + H2O(g) -> O2(g) +2HF(g) deltaH=-318kJ" This is what I did to solve the problem: PV=nRT -> PdeltaV=deltanRT deltaU=q+w w=-PdeltaV=-deltanRT q=deltaH=-318J (given) ...
Sun Jan 28, 2018 11:34 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Homework 8.49
Replies: 4
Views: 509

### Re: Homework 8.49

How did you get T=298?
Wed Jan 24, 2018 5:39 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Hmwk Q 8.31
Replies: 2
Views: 226

### Hmwk Q 8.31

For 8.31 "Calculate the heat released by 5.025 g of Kr(g) at 0.400atm as it cools from 97.6C to 25.0C at
(a) constant pressure and
(b) constant volume.
Assume that krypton behaves as an ideal gas. "

q=nCpdeltaT
Is there a table I need in the textbook that I should use to look up Cp?
Sun Jan 21, 2018 1:50 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Assigning system/surroundings
Replies: 5
Views: 336

### Re: Assigning system/surroundings

If heat is transferring from a metal to water, is the metal itself the system? Or do both the metal and water form the system?
Sun Jan 21, 2018 1:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Wed 01/17 Lecture
Replies: 1
Views: 126

### Wed 01/17 Lecture

On Wednesday 01/17,

"In a constant P calorimeter at 25C mix 50.0ml each of 1.0 M HCl and 1.0M NaOH. After mixing T=31.9C

How much heat is released?"

Why did Professor Lavelle say we needed to know the density of water?
Sat Jan 20, 2018 9:22 pm
Forum: Phase Changes & Related Calculations
Topic: What mass of SO2 must be evaporated?
Replies: 1
Views: 729

### What mass of SO2 must be evaporated?

"Before the introduction of chlorofluorocarbons, sulfur dioxide (enthalpy of vaporization, 6.00 kcal/mol) was used in household refrigerators. What mass of SO2 must be evaporated to remove as much heat as evaporation of 1.00 kg of CCl2F2 (enthalpy of vaporization is 17.4 kj/mol)? The vaporizati...
Sat Jan 20, 2018 2:55 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Replies: 8
Views: 3855

### Re: Isolated vs. Adiabatic system

Isolated systems have no contact with its surroundings. This means they cannot exchange matter or energy with the surroundings. From the textbook, "A system with adiabatic walls is not necessarily an isolated system: energy may be transferred to or from a system in an adiabatic container as wor...
Sat Jan 20, 2018 2:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q. 8.15
Replies: 1
Views: 118

### Q. 8.15

"Indicate whether each of the following statements about an adiabatic process in a closed system is always true, always false or true in certain conditions (specify the conditions):" a) delta U = 0 (true only if no work) d) deltaU = q (true if w=0) I got a little bit confused since the tex...
Tue Jan 16, 2018 1:33 pm
Forum: Phase Changes & Related Calculations
Topic: Homework Question 8.21
Replies: 1
Views: 133

### Re: Homework Question 8.21

Oh so I realized that it's q(water)= NEGATIVE q(copper)
Tue Jan 16, 2018 1:23 pm
Forum: Phase Changes & Related Calculations
Topic: Homework Question 8.21
Replies: 1
Views: 133

### Homework Question 8.21

" A piece of copper of mass 20.0 g at 100.0 degrees C is placed in a vessel of negligible heat capacity but containing 50.7 g of water at 22.0 degrees C. Calculate the final temperature of the water. Assume that no energy is lost to the surroundings. " I solved this by using q=mCsdeltaT an...