Search found 31 matches

by Rimsha Hussaini 1A
Mon Mar 11, 2019 11:49 am
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle
Replies: 3
Views: 66

Re: Le Chatelier's Principle

Le Chatelier's Pronciple says that chemical reactions adjust so as to minimize the effect od changes in concentration of molecules involved, changes in pressure, and changes in temperature. It indicates how ththe reaction will respond.
by Rimsha Hussaini 1A
Mon Mar 11, 2019 11:39 am
Forum: General Rate Laws
Topic: Are coefficients in rate laws?
Replies: 2
Views: 37

Re: Are coefficients in rate laws?

We raise each molecule's concentration to the power of the coefficient of that molecule in the balanced chemical equation. Therefore, it changes the value of the rate constant k in the rate law.
by Rimsha Hussaini 1A
Mon Mar 11, 2019 11:35 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium vs Steady-State Approach
Replies: 2
Views: 55

Pre-Equilibrium vs Steady-State Approach

As Professir Lavelle said in lecture, the pre-equilibrium approach is less flexible than the steady-state approach. Why is this true?
by Rimsha Hussaini 1A
Tue Mar 05, 2019 1:43 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 6th edition 14.47
Replies: 4
Views: 91

Re: 6th edition 14.47

I got 2.68 * 10^6 as well using ln, but why would we get just 10^6 (a completely different answer) by using log instead ln?
by Rimsha Hussaini 1A
Tue Mar 05, 2019 1:41 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: difference between galvanic and voltaic
Replies: 4
Views: 71

Re: difference between galvanic and voltaic

A voltaic cell refers to a galvanic cell and vice versa. A voltaic, aka a galvanic, cell is an electrochemical cell that derives electrical energy from the redox reactions within the cell.
by Rimsha Hussaini 1A
Tue Mar 05, 2019 1:32 pm
Forum: General Rate Laws
Topic: Unique Rate
Replies: 4
Views: 64

Re: Unique Rate

The unique rate refers to the unique average rate of reaction.
by Rimsha Hussaini 1A
Mon Feb 25, 2019 9:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reducing agent/oxidizing agent
Replies: 5
Views: 77

Re: Reducing agent/oxidizing agent

The reducing agent is the substance that undergoes oxidation (losing electrons) and thus corresponds to the anode.
by Rimsha Hussaini 1A
Mon Feb 25, 2019 9:15 pm
Forum: Balancing Redox Reactions
Topic: about redox reaction
Replies: 5
Views: 78

Re: about redox reaction

Redox reactions do not always include oxygen. For example, look at #13 from Chapter 14 in the 6th Edition. Not one of the cell reactions for the galvanic cells given, all of which are redox reactions, include oxygen.
by Rimsha Hussaini 1A
Mon Feb 25, 2019 9:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 6th Edition 14.13
Replies: 1
Views: 38

Re: 6th Edition 14.13

The anode corresponds to the oxidation half-reaction, and the cathode corresponds to the reduction half-reaction. In oxidation, the oxidation number of the element increases, and in reduction, the oxidation number of the element decreases. From Cl2(g)+H2(g) --> HCl(aq), Cl goes from a charge of 0 to...
by Rimsha Hussaini 1A
Mon Feb 25, 2019 9:01 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 2
Views: 46

Re: Salt Bridge

Yes, galvanic cells must have a salt bridge or a porous disk for the reason provided by the previous reply. The electron transfer from one reaction beaker to another will stop due to charge buildup, but the salt bridge or the porous disk will allow for ions to transfer and for the two solutions to r...
by Rimsha Hussaini 1A
Wed Feb 20, 2019 4:24 pm
Forum: Van't Hoff Equation
Topic: when to use
Replies: 4
Views: 74

Re: when to use

The van't Hoff equation describes the temperature dependence of K. It also relates the change in K to the change in temperature given the standard deltaH.
by Rimsha Hussaini 1A
Wed Feb 20, 2019 4:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anode v. Cathode
Replies: 9
Views: 136

Re: Anode v. Cathode

The anode is where electrical current flows in from outside and is the site of the oxidation half-reaction. The cathode where electrical current flows out and is the site of the reduction half-reaction.
by Rimsha Hussaini 1A
Wed Feb 20, 2019 4:13 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Salt Bridge
Replies: 5
Views: 71

Re: Salt Bridge

Without a salt bridge or a porous disk to allow ion transfer and to keep the two solutions neutral, electron transfer from one reaction beaker to the other will stop due to charge buildup.
by Rimsha Hussaini 1A
Mon Feb 11, 2019 9:23 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: q and w = 0
Replies: 3
Views: 79

Re: q and w = 0

If no heat was exchanged in the system, q = 0 and deltaU = w.
If no work was being done in the system, w = 0 and deltaU = q.
For an ideal gas in an isothermal system, deltaU = 0 = q + w. In this situation, q = nRTln(V2/V1).
by Rimsha Hussaini 1A
Mon Feb 11, 2019 5:51 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Question 8.19
Replies: 2
Views: 53

Re: Question 8.19

Again, adding the approach of adding the q of water and the q of copper together is correct. For the q of water, mcdeltaT=(400g)(4.18J/gK)(78K)=130.416kJ. For the q of copper, mcdeltaT=(500g)(0.385J/gK)(78K)=15.015kJ. We then add these two values together and, keeping in mind sig figs, we get 1.4*10...
by Rimsha Hussaini 1A
Tue Feb 05, 2019 12:40 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Important Thermochemistry Equations
Replies: 3
Views: 72

Re: Important Thermochemistry Equations

All of these equations will be given on a test, midterm, or final on the equation sheet, but it is also good to know how to derive some of these equations by knowing one or two of them.
by Rimsha Hussaini 1A
Tue Feb 05, 2019 12:07 pm
Forum: Calculating Work of Expansion
Topic: Work vs Degeneracy
Replies: 2
Views: 47

Re: Work vs Degeneracy

Degeneracy and work are two different concepts. As we learned in lecture, degeneracy is the number of ways of achieving a given energy state for particles like electrons. Work has to do with how energy enters or leaves a system. They simply share the letter that denotes them, though degeneracy is a ...
by Rimsha Hussaini 1A
Tue Feb 05, 2019 11:57 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q change and temperature
Replies: 2
Views: 58

Re: Q change and temperature

To phrase the previous answer slightly differently: Say the system in a piston undergoes expansion, which indicates that you are adding energy in the form of heat to the system and the system does work. There is no change in internal energy and, therefore, no change in temperature. Heat can be conve...
by Rimsha Hussaini 1A
Sun Feb 03, 2019 1:31 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Why Bond Enthalpies are the least accurate
Replies: 3
Views: 60

Re: Why Bond Enthalpies are the least accurate

A bond enthalpy is considered an estimate of the energy needed to break the average bond. Bonds can be either weakened or strengthened depending on the other atoms in the molecule associated with the bond and would need either less or more energy to break. Therefore, the bond enthalpy can be slightl...
by Rimsha Hussaini 1A
Sun Feb 03, 2019 1:21 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Negative or Positive Work
Replies: 3
Views: 60

Re: Negative or Positive Work

Another way to think about this is when work is being done by the system (or works on the surroundings), work is negative. The system's energy also decreases. When the surroundings do work on the system, it's positive.
by Rimsha Hussaini 1A
Sun Feb 03, 2019 1:14 pm
Forum: Phase Changes & Related Calculations
Topic: State Function
Replies: 10
Views: 102

Re: State Function

A state property is one whose value is determined by its current state. It is not dependent on the path taken to obtain that state. Work does depend on the path taken and is related to the change in energy when a system moves from one state to another. Therefore, work is not a state property.
by Rimsha Hussaini 1A
Mon Jan 21, 2019 6:39 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: pH of weak acid and its salt
Replies: 2
Views: 59

Re: pH of weak acid and its salt

I believe Professor Lavelle mentioned that, if we wanted, we could include and write out the potassium as K+ on both sides of the equation. Nitrous acid stays as one molecule when in water, but potassium nitrite, as a salt, dissociates in water to form NO2- and K+. That NO2- is included in the HNO2 ...
by Rimsha Hussaini 1A
Mon Jan 21, 2019 6:12 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: 7th Edition 6B.9
Replies: 2
Views: 55

Re: 7th Edition 6B.9

Yes, very strong acids can have negative pH values.
by Rimsha Hussaini 1A
Mon Jan 21, 2019 6:11 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Post Assessment
Replies: 1
Views: 49

Re: Post Assessment

Whether or not a reaction is exothermic depends on the delta H. If the delta H is positive, then the reaction is endothermic. If the delta H is negative, then the reaction is exothermic. For an endothermic reaction, if the temperature is increased, the forward reaction is favored and the equation wi...
by Rimsha Hussaini 1A
Tue Jan 15, 2019 8:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Polyprotic Acids
Replies: 2
Views: 39

Re: Polyprotic Acids

Any acid that contains more than one H+ per molecule is a polyprotic acid. Therefore, any acid that contains more than one H+ per molecule will donate its H+. I believe that the number of protonations will not be specified because it is assumed that the reaction will go to completion and all of the ...
by Rimsha Hussaini 1A
Tue Jan 15, 2019 1:39 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: question from module
Replies: 4
Views: 80

Re: question from module

When the volume of a system is compressed, the effect on the system depends on how many moles are on each side of the equation. If the moles of the reactants equal the moles of the products, like in this situation, the change in volume has an equal effect on the reactants and the products. Thus, the...
by Rimsha Hussaini 1A
Tue Jan 15, 2019 1:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculate pOH
Replies: 3
Views: 39

Re: Calculate pOH

To put it simply, yes.

The chemical equation of the dissociation of Ba(OH)2 is Ba(OH)2 -> 2OH- + Ba2+
This indicates that in the dissociation of Ba(OH)2, 2 hydroxide ions form.
by Rimsha Hussaini 1A
Fri Jan 11, 2019 4:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle [ENDORSED]
Replies: 3
Views: 48

Re: Le Chatelier's Principle [ENDORSED]

When we increase the concentration of a substance like we did with the N2 and the NH3, the reaction moves to the right (the products) and to the left (the reactants), respectively. When we increase N2, the reaction produces more of the NH3 to use up that excess N2. When we increase NH3, the reaction...
by Rimsha Hussaini 1A
Fri Jan 11, 2019 12:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Quadratic Equations
Replies: 3
Views: 51

Re: Quadratic Equations

There will only ever be one plausible answer to the quadratic equation because there cannot be two concentrations of a substance at a given temperature and with the given molar concentrations of the other substance.
by Rimsha Hussaini 1A
Tue Jan 08, 2019 4:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.13c (6th Edition)
Replies: 2
Views: 52

11.13c (6th Edition)

Hey! I was hoping someone could clarify 11.13 part c for me. CO_{3}^{2-} (aq) + 2H_{3}O^{+} (aq)\rightarrow CO_{2} (g) + 3H_{2}O (l) Because there are aqueous and gaseous reactants and products, my approach to this question was to use molar concentrations, not partial...

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