Search found 32 matches
- Tue Mar 12, 2019 5:12 pm
- Forum: Second Order Reactions
- Topic: 7B.13 Help
- Replies: 4
- Views: 500
Re: 7B.13 Help
1/16= (1/2)^4, so that means 4 times the halflife. 1/4=(1/2)^2 so 2 times the halflife. for part c, use the second order reaction
- Tue Mar 12, 2019 4:59 pm
- Forum: First Order Reactions
- Topic: Rate dependency
- Replies: 5
- Views: 564
Re: Rate dependency
the rate depends on the reactants initially, over time the products will decompose back into reactants as they reach equilibrium, but initially it only matters on reactants (assuming temperature and all other factors are constant)
- Tue Mar 12, 2019 4:52 pm
- Forum: First Order Reactions
- Topic: 7B.9
- Replies: 3
- Views: 418
Re: 7B.9
if you use the formula of 1 over the molar coefficient one can find the change in [a] as a ratio of change of [b]
- Wed Mar 06, 2019 9:37 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Order of the reactant (n)
- Replies: 4
- Views: 521
Re: Order of the reactant (n)
If you change the concentration of reactant and the amount of product changes by the same amount, n is 1. If product changes by a higher value than your reactant, take the value the reactant was changed by and see to what power it must be raised by to get the same value as the product
- Wed Mar 06, 2019 9:33 am
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: k values
- Replies: 4
- Views: 552
Re: k values
K depends on the order of the reaction, because the concentrations of the reactants are raised to different powers.
- Wed Mar 06, 2019 9:31 am
- Forum: General Rate Laws
- Topic: overall reaction rate
- Replies: 2
- Views: 295
Re: overall reaction rate
Depending on the order of said reaction one can figure out k and the concentration of the products at certain times
- Wed Feb 27, 2019 4:38 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: moles of electrons of reaction
- Replies: 3
- Views: 346
Re: moles of electrons of reaction
usually one can look at the amount of electrons in the redox half reaction, which shows how many moles of electrons were used.
- Wed Feb 27, 2019 4:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E and Spontaneity
- Replies: 2
- Views: 281
Re: E and Spontaneity
a positive E means that the reaction will create energy, "exothermic" in a sense, with no need to put in heat to start the reaction. This is the opposite for negative E values, which are "endothermic" and require energy for the reaction to proceed
- Wed Feb 27, 2019 4:34 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: 14.119
- Replies: 2
- Views: 771
Re: 14.119
redox reactions are net ionic, meaning the ions that do not change charge in the reaction are left out
- Fri Feb 22, 2019 11:43 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electrode Potential
- Replies: 2
- Views: 293
Re: Electrode Potential
The reaction will theoretically create the same voltage at all times, this just means that it is always the same so there is no difference in how we calculate it
- Wed Feb 20, 2019 2:16 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Positive vs Negative E value
- Replies: 5
- Views: 5610
Re: Positive vs Negative E value
The E value does not depend on the right or left, it is on the E potential of the cathode and anode.
- Wed Feb 20, 2019 2:15 pm
- Forum: Balancing Redox Reactions
- Topic: Galvanic cells
- Replies: 4
- Views: 440
Galvanic cells
What happens in an electric current and cell when there is no transfer of extra ions from solution to solution?
- Wed Feb 20, 2019 12:12 pm
- Forum: Balancing Redox Reactions
- Topic: Trends
- Replies: 5
- Views: 474
Re: Trends
There are several molecules that are fairly constant in their oxidation state, such as Oxygen with -2 or Hydrogen with +1. Most of the metals can go either way.
- Fri Feb 15, 2019 12:06 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Quick Conceptual question
- Replies: 7
- Views: 957
Re: Quick Conceptual question
Entropy is the amount of chaos in the system, while enthalpy is the heat released
- Fri Feb 15, 2019 12:05 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Gibbs Free Energy and Equilibrium
- Replies: 5
- Views: 530
Re: Gibbs Free Energy and Equilibrium
The reaction is "at completion" so there is nothing spontaneous to drive the reaction forward or backward
- Tue Feb 12, 2019 9:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
- Replies: 49
- Views: 11794
Re: Lyndon's HOTDOG MIDTERM REVIEW SESSION!! FINALLY!
can someone explain how to do #5
- Sun Feb 10, 2019 6:56 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: 4I.1
- Replies: 1
- Views: 1787
4I.1
In this question it asks "what is the total entropy change when 40kJ of heat are transferred from a large reservoir at 800K to one at 200K.
Why wouldn't the total entropy change either be zero, because one lost entropy and the other gained it, or be (q/T)?
Why wouldn't the total entropy change either be zero, because one lost entropy and the other gained it, or be (q/T)?
- Wed Feb 06, 2019 10:32 am
- Forum: Calculating Work of Expansion
- Topic: Isothermal Expansions
- Replies: 3
- Views: 381
Re: Isothermal Expansions
They can be both, reversible means that the external pressure is equal to the pressure of the gas and slowly increases/decreases with the gas pressure according to if it is expanding or being compressed, respectively. A irreversible reaction is one where the external pressure is constant, and one do...
- Wed Feb 06, 2019 10:23 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Isothermic definition
- Replies: 5
- Views: 909
Re: Isothermic definition
Isothermic means constant temperature, isometric means same chemical formula but different arrangement in 3D space
- Wed Feb 06, 2019 10:08 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: enthalpy unit
- Replies: 3
- Views: 416
Re: enthalpy unit
Usually one assumes that a certain amount of energy (joules) is released or used up during a reaction of 1 mole. Therefore it can be J/mol or kJ/mol
- Wed Jan 30, 2019 11:12 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Most stable form enthalpy
- Replies: 3
- Views: 468
Re: Most stable form enthalpy
Let's look at the reaction of 2H2O2->2H2O + O2
Even though hydrogen peroxide is broken up into water an oxygen, the O2 is in it's natural or most occuring form and therefore doesn't take energy or release energy to be created
Even though hydrogen peroxide is broken up into water an oxygen, the O2 is in it's natural or most occuring form and therefore doesn't take energy or release energy to be created
- Wed Jan 30, 2019 11:05 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Isolated systems
- Replies: 10
- Views: 822
Re: Isolated systems
An isolated system's internal energy stays constant or increases, so it's unlikely for it to have a changing volume
- Wed Jan 30, 2019 11:00 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy
- Replies: 4
- Views: 385
Re: Enthalpy
The enthalpy of reaction is made up of the separate enthalpies of formation for the molecules involved
- Wed Jan 23, 2019 6:37 pm
- Forum: Phase Changes & Related Calculations
- Topic: Endothermic or Exothermic
- Replies: 20
- Views: 2070
Re: Endothermic or Exothermic
Exothermic, one can look at the reverse, which is endothermic, when one sweats and the body heat is used up to vaporize the sweat.
- Wed Jan 23, 2019 6:36 pm
- Forum: Phase Changes & Related Calculations
- Topic: How to tell acids and bases
- Replies: 8
- Views: 622
Re: How to tell acids and bases
Usually acids have an extra H on either the end or beginning of the chemical formula, and bases have an OH group.
- Wed Jan 23, 2019 6:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Water turning into ice rapidly
- Replies: 2
- Views: 164
Re: Water turning into ice rapidly
this only works with distilled water, where the water molecules do not have something to bond around in their crystalline pattern, however when one shakes or disturbs the water, they molecules are jostled into place and freeze.
- Fri Jan 18, 2019 11:16 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Net Ionic Equations
- Replies: 3
- Views: 366
Re: Net Ionic Equations
Net ionics just takes the reactants and only leaves the molecules/ions that changed from one reaction to the other.
- Fri Jan 18, 2019 11:14 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: The Quadratic Equation
- Replies: 3
- Views: 189
Re: The Quadratic Equation
Bypassing the quadratic equation because when on the bottom of the (x^2)/(concentration-x), the x, or change in concentration, is so small that the concentration is basically untouched and it is needless to use it. Therefore the equation becomes (x^2)/concentration. Then it's very easy to solve for ...
- Fri Jan 18, 2019 11:12 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Ka vs. Kb
- Replies: 12
- Views: 4650
Re: Ka vs. Kb
K is the letter that denotes an equilibrium reactions quotient, the c is just denoting it's a non-acid /base reaction, a for acid, b for base.
- Sat Jan 12, 2019 2:37 pm
- Forum: Ideal Gases
- Topic: Q and K [ENDORSED]
- Replies: 35
- Views: 3236
Re: Q and K [ENDORSED]
Since they have the same formula, it is just a view of the value of the products and reactants and using this value to see how it applies to the equilibrium constant.
- Wed Jan 09, 2019 4:08 pm
- Forum: Ideal Gases
- Topic: K values
- Replies: 3
- Views: 300
K values
Since K values smaller than 10^-3 are considered small, and large ones are greater than 10^3, what do the values between 10^-3 and 10^3 represent?
- Wed Jan 09, 2019 4:06 pm
- Forum: Ideal Gases
- Topic: Ideal vs Real Gas
- Replies: 6
- Views: 550
Re: Ideal vs Real Gas
One could use the van der waals equation to see the difference between real and ideal gases.