Search found 31 matches

by Britney Alvey 1B
Tue Mar 13, 2018 2:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: question 15.47
Replies: 4
Views: 114

Re: question 15.47

The solution manual classifies the Cl ion as an intermediate.
by Britney Alvey 1B
Tue Mar 13, 2018 2:17 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2 #6b
Replies: 2
Views: 95

Re: Test 2 #6b

The reducing agent is the species that loses an electron. Ag goes from a neutral state to an oxidation state of +1. AgF stays neutral so this would mean Ag has to be the reducing agent.
by Britney Alvey 1B
Tue Mar 13, 2018 2:09 pm
Forum: Balancing Redox Reactions
Topic: Test 2 #1
Replies: 6
Views: 240

Re: Test 2 #1

O has a charge of -2, and since there is 2 molecules of O the total charge of the O2 species is -4. The molecule CO2 is neutral, so that would mean that C has to have a charge of +4 to balance the charge of the O.
by Britney Alvey 1B
Sat Mar 10, 2018 4:37 pm
Forum: Zero Order Reactions
Topic: Zero Order and Catalysts [ENDORSED]
Replies: 2
Views: 273

Re: Zero Order and Catalysts [ENDORSED]

Zero order reactions typically take place when a catalyst is needed for the reaction to occur. The catalyst will be saturated by the reactants and the rate of the reaction will not depend on the concentration of the reactants.
by Britney Alvey 1B
Sat Mar 10, 2018 3:26 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: SN2 Organic Reaction
Replies: 3
Views: 91

Re: SN2 Organic Reaction

Yes. The nucleophile will donate an electron pair to form a chemical bond.
by Britney Alvey 1B
Sat Mar 10, 2018 3:23 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Molecularity and Coefficients
Replies: 3
Views: 123

Re: Molecularity and Coefficients

The reaction 2 A --> B + C would be bimolecular.
by Britney Alvey 1B
Wed Feb 28, 2018 7:25 pm
Forum: First Order Reactions
Topic: Terminology "first-order" [ENDORSED]
Replies: 5
Views: 158

Re: Terminology "first-order" [ENDORSED]

You can refer to the order of individual reactants as well as the order of the reaction. The overall order of the reaction is the sum of the orders of each reactant. So, if each reactant has order 1 then the order of the reaction is 2.
by Britney Alvey 1B
Wed Feb 28, 2018 5:54 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: units of K
Replies: 5
Views: 157

Re: units of K

For 0 order reactions, the units for k are are mol/(L*s). For 1st order reactions, the units of k are s^(-1). For 2nd order reactions, the units for k are L/(mol*s).
by Britney Alvey 1B
Wed Feb 28, 2018 5:47 pm
Forum: General Rate Laws
Topic: Negative Signs [ENDORSED]
Replies: 6
Views: 203

Re: Negative Signs [ENDORSED]

You always want to work with positive reaction rates.
by Britney Alvey 1B
Sat Feb 24, 2018 11:15 pm
Forum: General Rate Laws
Topic: Reactants Rate Law
Replies: 2
Views: 98

Re: Reactants Rate Law

In class we discussed that for a recation with one reactant and two products such as aA-->bB+cC that rate= (1/a)(dA/dt) = (1/b)(dB/dt) = (1/c)(dC/dt). So, if there was instead two reactants such as aA+bB--->cC+dD then just account for the additional reactant so, rate= (1/a)(dA/dt) = (1/b)(dB/dt) = (...
by Britney Alvey 1B
Sat Feb 24, 2018 11:09 pm
Forum: Balancing Redox Reactions
Topic: Oxidation state
Replies: 4
Views: 144

Re: Oxidation state

Yes, you should take into account the coefficients when determining oxidation states.
by Britney Alvey 1B
Sat Feb 24, 2018 11:07 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.41b. Homework b
Replies: 2
Views: 129

Re: 14.41b. Homework b

When you get the balanced equation, everything has a stoichiometric coefficient of 2. You can simplify this by dividing the whole balanced equation by 2 which also divides n by 2 resulting in n=1.
by Britney Alvey 1B
Tue Feb 13, 2018 11:19 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 11.15
Replies: 2
Views: 121

Re: 11.15

The question states that the reaction is happening at 1200K so you would use this value to calculate deltaG. The solutions manual calculates delta G not . This is an important distinction because would be calculated at 298K by definition.
by Britney Alvey 1B
Tue Feb 13, 2018 11:14 am
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: 8.33
Replies: 1
Views: 78

Re: 8.33

The question asks for Cv. The Cv vaule for polyatomic gases is 3*R. The value 7/2*R is the Cp value for diatomic molecules. You can reference the table on page 281 in the book which lists the Cv and Cp values for ideal gases.
by Britney Alvey 1B
Tue Feb 13, 2018 11:06 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: practice midterms
Replies: 2
Views: 127

Re: practice midterms

There was a practice midterm from a review session posted on chemistry community. You should be able to find it if you search "practice midterm winter 2018".
by Britney Alvey 1B
Sat Feb 10, 2018 7:47 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Oxidation
Replies: 4
Views: 87

Re: Oxidation

Oxidation takes place in the anode(left side) of the galvanic cell.
by Britney Alvey 1B
Sat Feb 10, 2018 7:45 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Commas in Cell Diagram
Replies: 2
Views: 85

Re: Commas in Cell Diagram

A comma is used when the phases of the two elements in contact are the same. For example, you would use a comma for something like Fe3+(aq),Fe2+(aq). A | is used when the phases of the two elements in contact are in different phases. For example: Cu(s)|Cu2+(aq). A | can also indicate that a pourous ...
by Britney Alvey 1B
Sat Feb 10, 2018 7:39 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: 9.35
Replies: 2
Views: 105

Re: 9.35

The problem states that in box A, there is a monoatomic gas, meaning that there are single atoms of gas. The Cv value for atoms is 3/2R. In box B, there are diatomic molecules that are not vibrationally active, meaning these are linear molecules. For linear molecules, the Cv value is 5/2R. In box C,...
by Britney Alvey 1B
Sat Feb 03, 2018 5:50 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Entropy Changes Due to Change in Pressure
Replies: 2
Views: 66

Re: Entropy Changes Due to Change in Pressure

It is always good to remember that pressure is inversely proportional to volume.
by Britney Alvey 1B
Sat Feb 03, 2018 5:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.65
Replies: 6
Views: 179

Re: 9.65

Write a balanced chemical equation for each compound and calculate the standard entropies of formation. If the standard entropy of formation is negative, then the compound will be less stable at a higher temperature. If the standard entropy of formation is positive, the compound will be more stable ...
by Britney Alvey 1B
Sat Feb 03, 2018 4:17 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: Difference between deltaS(tot), deltaS and deltaS(surr)
Replies: 5
Views: 128

Re: Difference between deltaS(tot), deltaS and deltaS(surr)

I agree with the comments above. It is also worth noting that conceptually, deltaS(tot) is the change in entropy of the universe, the combination of deltaS and deltaS of the surroundings. DeltaS is the change in entropy of the system and deltaS(surr) is the change in entropy of the surroundings, mea...
by Britney Alvey 1B
Tue Jan 23, 2018 2:53 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Standard state
Replies: 2
Views: 79

Re: Standard state

The standard state of an element is the state it is in at 25 and 1 atm of pressure.
by Britney Alvey 1B
Tue Jan 23, 2018 2:50 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heat Capacities of Gas
Replies: 1
Views: 71

Re: Heat Capacities of Gas

The equations on page 281 are showing the specific heat capacity for ideal gases under constant volume and constant pressure. When under constant volume, depending on if you're considering an atom, linear molecule, or a non linear molecule, you would use the respective C_{V} value. Similarly, for co...
by Britney Alvey 1B
Tue Jan 23, 2018 2:39 pm
Forum: Calculating Work of Expansion
Topic: work of expansion formula
Replies: 1
Views: 68

Re: work of expansion formula

When a system does work of expansion, it is is working against an external pressure and therefore losing energy. Since, \Delta U= q+w , the negative sign ensures that it is understood that the work being done by a system results in a loss of energy since the system is doing work instead of work bein...
by Britney Alvey 1B
Tue Jan 16, 2018 9:33 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy of formation vs reaction enthalpy
Replies: 2
Views: 77

Re: Enthalpy of formation vs reaction enthalpy

Reaction enthalpy is the change in heat that occurs when a reaction takes place. To calculate this, you would add the different \Delta H 's of each reaction that took place in order to form the product, i.e. Hess's Law. The enthalpy of formation is the change in enthalpy when an element in its stand...
by Britney Alvey 1B
Tue Jan 16, 2018 9:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.67 part a
Replies: 1
Views: 54

Re: 8.67 part a

If you reference table 8.4 in the textbook it lists some standard enthalpies of formation, including water. For water, \Delta H_{f}^{^{\circ}} = -242 kJ/mol. However if you didn't recognize that number, you could also think about how both of the reactants are in a gaseous phase and by adding up the ...
by Britney Alvey 1B
Tue Jan 16, 2018 9:03 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity: U vs H
Replies: 2
Views: 100

Re: Heat Capacity: U vs H

By definition, enthalpy measures the change in heat at constant pressure. So, when finding , it will always be at constant pressure.
by Britney Alvey 1B
Thu Jan 11, 2018 2:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Homework Problem 8.21
Replies: 4
Views: 197

Re: Homework Problem 8.21

All heat lost by the copper is going to be gained by the water. Therefore, q_{metal}=-q_{water} . q=mC\Delta T , where m=mass, C=specific heat capacity, and \Delta T = the change in temperature.The specifc heat capacity of copper is 0.38 J.^{\circ}C^{-1}.g^{-1} and the specific heat capacity of wate...
by Britney Alvey 1B
Wed Jan 10, 2018 10:21 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.73a
Replies: 1
Views: 97

Re: 8.73a

In this reaction, the C-H bonds are already formed in the C2H2 moleules. Each C2H2 molecule will look like H-C-C-H with the C-C being a triple bond. When the reaction happens, the triple bonds between the carbons are broken and the only new bonds formed are going to be between the carbons since the ...
by Britney Alvey 1B
Wed Jan 10, 2018 10:07 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Conceptualizing enthalpy
Replies: 2
Views: 189

Re: Conceptualizing enthalpy

1. q_{p} is the heat of the system at constant pressure. 2. It might help if you look at it this way: \Delta H = \Delta U +PV . If you assume that the system can only do expansion work then you can substitute in that \Delta U=q+w and w=-P_{ex}\Delta V . Also, because the system is at a constant pres...
by Britney Alvey 1B
Thu Oct 05, 2017 5:50 pm
Forum: Balancing Chemical Reactions
Topic: Fundamentals H.21
Replies: 2
Views: 427

Re: Fundamentals H.21

This is the way I balanced this equation: C10H15N + O2 ---> CO2 + H2O + CH4N2O Step 1 : Balance N since it appears the least 2C10H15N + O2 ---> CO2 + H2O + CH4N2O Step 2: Balance H, there are 30 H on the right side and only 2 H and 4 H, leaving the 4 H alone, that would be 30-4= 26/2= 13 as your coe...

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