## Search found 30 matches

Sun Mar 18, 2018 5:54 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8245
Views: 1442595

### Re: Post All Chemistry Jokes Here

what kind of fish has only 2 sodium atoms?
2 Na
Sun Mar 18, 2018 5:48 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8245
Views: 1442595

### Re: Post All Chemistry Jokes Here

I don't like atoms, I heard they make up everything...
Sun Mar 18, 2018 5:41 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8245
Views: 1442595

### Re: Post All Chemistry Jokes Here

If a king farts, is it a noble gas?
Sun Mar 11, 2018 11:56 pm
Forum: General Rate Laws
Topic: Rate law constant
Replies: 4
Views: 272

### Rate law constant

Can rate law constant ever be negative?
Sun Mar 11, 2018 11:55 pm
Forum: Zero Order Reactions
Topic: Half life
Replies: 7
Views: 784

### Half life

Can we use the half life formulas for zero order and second order in practical life examples?
Sun Mar 11, 2018 9:04 pm
Forum: First Order Reactions
Topic: Slope of 1st order RXNs
Replies: 9
Views: 688

### Re: Slope of 1st order RXNs

The integrated formula derived for the first order is [At] = [A0]*e^-kt. This gives an exponential graph of [At] against time and a decreasing graph with the slope of -k when graphed for ln[At] against time.
Sun Mar 04, 2018 5:12 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: reaction mechanism
Replies: 2
Views: 191

### Re: reaction mechanism

Let's say, if the first step of the reaction is the slowest step, the overall reaction cannot proceed any faster than this first elementary step. So the slowest step is always the rate- limiting step and therefore it determines the overall rate of the reaction.
Sun Mar 04, 2018 11:38 am
Forum: First Order Reactions
Topic: First Order- Half life
Replies: 1
Views: 160

### First Order- Half life

Why does the first order half life not depend on the initial concentration of reactant? Also, would higher temperature of the reaction lead to a slower half life?
Thu Mar 01, 2018 1:45 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetically Stable Vs. Thermodynamically Stable
Replies: 4
Views: 1039

### Re: Kinetically Stable Vs. Thermodynamically Stable

Kinetic stability deals with the rate of reaction. The slower the reaction, the more kinetically stable the reaction is. Thermodynamic stability deals with the spontaneity of the reaction, which depends on the Gibbs free energy. Graphite is more thermodynamically stable than diamond. But the reactio...
Sun Feb 25, 2018 9:55 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetics vs Thermodynamics
Replies: 7
Views: 512

### Re: Kinetics vs Thermodynamics

Kinetic stability deals with the rate of the reaction. The slower the reaction, greater the kinetic stability. Whereas thermodynamic stability will depend on whether the reaction is spontaneous or not.
Sun Feb 25, 2018 9:49 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Homework 15.19
Replies: 3
Views: 296

### Re: Homework 15.19

I think I read in the one of the examples in textbook (15.1) that its just better practice to choose multiple of units that minimize the power of 10 shown explicitly.
Sun Feb 25, 2018 9:44 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: unique average rates
Replies: 3
Views: 338

### Re: unique average rates

Unique rate is positive for the product being formed and negative for the reactant/s being used up. This rate should be the same for the reactants and products in a chemical reaction. Its basically the rate of appearance/disappearance of reactant/products divided by their stoichiometric coefficients.
Sun Feb 18, 2018 8:39 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Q
Replies: 7
Views: 429

### Re: Q

Q is usually used to determine which direction the reaction will have to shift towards to reach chemical equilibrium.
Sun Feb 18, 2018 8:34 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Work when pressure is constant
Replies: 6
Views: 530

### Re: Work when pressure is constant

Yes, we can only use W=-P delta V, for a constant external pressure i.e irreversible reaction.
Sun Feb 18, 2018 8:29 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Anodes vs. Cathodes
Replies: 3
Views: 221

### Re: Anodes vs. Cathodes

When the cell is spontaneous, the one with the highest reduction potential should be the reduction half-reaction and so it should act as the cathode. The one with the lower reduction potential as the oxidation-half reaction and so it should act as the anode.
Sun Feb 11, 2018 10:26 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: delta S(system) vs delta S(surroundings)
Replies: 4
Views: 4199

### Re: delta S(system) vs delta S(surroundings)

delta S (universe)= delta S (sys) + delta S (surr)
When the reaction is at equilibrium and it is a reversible reaction, the total delta S of the universe is zero.
Hence, delta S (sys) = - delta S (surr) for these conditions.
Sun Feb 11, 2018 10:23 pm
Forum: Calculating Work of Expansion
Topic: Reversible vs Irreversible
Replies: 2
Views: 235

### Re: Reversible vs Irreversible

When it is reversible work, we use the equation W=-nRTln(v2/v1)
When it is irreversible work, W= -Pext (v2-v1)
Sun Feb 11, 2018 10:19 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: Isothermic
Replies: 4
Views: 342

### Re: Isothermic

For a system,
Isothermic = constant temperature
Isochoric= constant volume
Isobaric= constant pressure
Isometric= constant dimensions or measure
Sun Feb 04, 2018 6:13 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Replies: 3
Views: 211

### Re: Question about "Real Processes"

During a process, energy cannot be completely transferred. Some of the transformational energy will be dissipated in the surrounding environment as heat during the process This energy cannot be recovered, therefore it is not a reversible process.
Sun Feb 04, 2018 6:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Delta U (Concept Clarification)
Replies: 6
Views: 307

### Re: Delta U (Concept Clarification)

There is no net change in internal energy as all the heat is used to to do expansion work against the surroundings.
Sun Feb 04, 2018 5:57 pm
Forum: Van't Hoff Equation
Topic: Van't Hoff Eq.
Replies: 2
Views: 182

### Re: Van't Hoff Eq.

Van't Hoff equation accounts for the Le Chateliers Principle we learned earlier, it is useful to understand effect of temperature on equilibrium.
Sun Jan 28, 2018 2:49 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 6
Views: 410

An example of adiabatic system could be when change in temperature = 0, no heat flow(q=0), but work is being done, like in an insulated container with the gas filled in it expanding.
Sun Jan 28, 2018 1:42 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: Third Law of Thermodynamics
Replies: 4
Views: 278

### Re: Third Law of Thermodynamics

Also, absolute zero is a theoretical concept. It may not be achieved experimentally. This is because from the second law of thermodynamics, we know that heat will spontaneously move from a warmer body to a cooler body, so the object that one tries to cool to absolute zero will try to take in heat fr...
Sun Jan 28, 2018 1:32 pm
Forum: Calculating Work of Expansion
Topic: The integral equation
Replies: 8
Views: 397

### Re: The integral equation

I believe we are expected to understand how the equations come into place, however I doubt that we would actually need to do calculations to derive the equation on the test.
Sun Jan 21, 2018 7:14 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Heat Capacity vs Specific Heat Capacity
Replies: 2
Views: 167

### Re: Heat Capacity vs Specific Heat Capacity

Heat Capacity is the ratio of heat supplied/absorbed to the corresponding rise in the temperature; in other words it is the amount of heat required to raise the temperature of a substance by 1 degree C. But this does not tell us how much mass of the substance we are measuring. Heat capacity is an ex...
Sun Jan 21, 2018 6:49 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Heat versus work
Replies: 6
Views: 360

### Re: Heat versus work

I found it interesting that although work and heat are interchangeable forms of energy, while work can be fully transferred into heat, the vice versa is not true. This is because if heat is fully transformed into work, it would violate the laws of entropy, i.e, a closed system's entropy cannot decre...
Sun Jan 21, 2018 6:38 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: isolated sytems
Replies: 4
Views: 259

### Re: isolated sytems

Also, it seems very hard to find a truly isolated system, except for the universe as a whole, because we have to account for the gravity on any system with mass.
Wed Jan 10, 2018 4:45 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 5
Views: 228

### Re: Bond Enthalpies

Yes, ΔH= (energy needed to break the reactant bonds) - (energy released by forming the product bonds) gives the change in enthalpy for the reaction
Wed Jan 10, 2018 4:16 pm
Forum: Phase Changes & Related Calculations
Topic: State Properties: q vs. qp
Replies: 3
Views: 515

### Re: State Properties: q vs. qp

Work is a state property as it is directly proportional to the object's distance moved against the opposing force and this distance depends on the path taken. Since deltaU = W + q, and work is a state function, it seems that the heat given off must be dependent on the path as well.
Mon Jan 08, 2018 5:13 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: The First Law: Problem 8.3
Replies: 2
Views: 221

### Re: The First Law: Problem 8.3

When the air is compressed, work is done ON the system(i.e. air) by the surrounding, which increases the internal energy of the system and hence the work wrt air is positive. If I'm understanding the hypothetical correctly, if the air expands, work is done BY the system(air) on the surrounding(pump ...