## Search found 32 matches

Tue Mar 12, 2019 5:12 pm
Forum: Second Order Reactions
Topic: 7B.13 Help
Replies: 4
Views: 225

### 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: 258

### 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: 163

### 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: 221

### 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: 288

### 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: 138

### 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: 127

### 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: 100

### 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: 531

### 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: 134

### 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: 3121

### 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: 174

### 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: 179

### 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: 350

### 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: 190

### 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: 4071

### 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: 142

### 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)?
Wed Feb 06, 2019 10:32 am
Forum: Calculating Work of Expansion
Topic: Isothermal Expansions
Replies: 3
Views: 169

### 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: 281

### 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: 179

### 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: 235

### 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
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: 295

### 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: 171

### 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: 953

### 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: 286

### 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: 79

### 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: 169

### 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: 84

### 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: 759

### 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: 1791

### 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: 166

### 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: 261

### Re: Ideal vs Real Gas

One could use the van der waals equation to see the difference between real and ideal gases.

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