Search found 24 matches

by LilyL1C
Thu Mar 14, 2019 5:41 pm
Forum: Second Order Reactions
Topic: second order half life calculation
Replies: 1
Views: 56

Re: second order half life calculation

No you cannot. If you do one half life, you'll end up with half of the initial concentration. If you take another half life, you get 1/4 of the initial concentration. Another half life, and it's 1/8. One more half life, and you finally get 1/16. So it was 4 half lives, which is (1/2)^4 = 1/16. You n...
by LilyL1C
Thu Mar 14, 2019 5:31 pm
Forum: General Rate Laws
Topic: rate laws
Replies: 6
Views: 95

Re: rate laws

No they do not. You can find the exponents of rate laws by comparing the rates of two reactions, or they will be given in an experimental rate law.
by LilyL1C
Thu Mar 14, 2019 5:29 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Reaction mechanisms and slowest step
Replies: 1
Views: 52

Re: Reaction mechanisms and slowest step

The problem will usually tell us which is the slow step and which is the fast step. Also, in the problem that Lavelle gave us in class, the first step was the fast step and the second step was the slow step. That's why he was talking about the "bottle neck" and how the first step was basic...
by LilyL1C
Thu Mar 07, 2019 6:15 pm
Forum: Zero Order Reactions
Topic: how do we tell if a reaction is zero order?
Replies: 5
Views: 114

Re: how do we tell if a reaction is zero order?

A zero order reaction will have a rate law that does not depend on the concentrations of the reactants. It will proceed at the same rate no matter what. You can also make a graph of [A] vs. time, and if you get a straight line with a negative slope, that tells you that the reaction is zeroth order.
by LilyL1C
Thu Mar 07, 2019 6:12 pm
Forum: Balancing Redox Reactions
Topic: balancing water
Replies: 8
Views: 182

Re: balancing water

whether you cancel out your water molecules early on or later doesn't make a difference in the final answer, and you can do it either way.
by LilyL1C
Thu Mar 07, 2019 6:09 pm
Forum: General Rate Laws
Topic: 7A.17 7th Edition
Replies: 1
Views: 51

Re: 7A.17 7th Edition

the book converted the units from mMolarity to Molarity, which makes their answer much greater. 2.85 is the answer you would get if you kept the original units of mM.
by LilyL1C
Fri Feb 22, 2019 9:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cathode vs. Anode
Replies: 9
Views: 134

Re: Cathode vs. Anode

Oxidation occurs at the anode, and reduction occurs at the cathode. The electrons will be flowing from the anode to the cathode, and so the anode will be marked with a negative sign and the cathode will be marked with a positive sign.
by LilyL1C
Fri Feb 22, 2019 9:46 pm
Forum: Balancing Redox Reactions
Topic: OH-, Adams, Disc 1A
Replies: 3
Views: 61

Re: OH-, Adams, Disc 1A

It would depend on each question and if the reaction was taking place in an acidic solution or a basic solution. And the question would specify which reaction it is. If it's an acidic solution, you add H+ and water; if it's a basic solution, you add OH- and water.
by LilyL1C
Fri Feb 22, 2019 9:42 pm
Forum: Balancing Redox Reactions
Topic: Acidic Vs. Basic Redox Rxn
Replies: 3
Views: 77

Re: Acidic Vs. Basic Redox Rxn

It should specify in each question if the reaction is taking place in an acidic solution or a basic solution. Then you can add hydroxides or hydroniums as needed.
by LilyL1C
Fri Feb 15, 2019 10:37 pm
Forum: Calculating Work of Expansion
Topic: 4F.1 7th Edition
Replies: 4
Views: 94

Re: 4F.1 7th Edition

The heat of the system is equal and opposite to the heat of the surroundings. qsystem = -qsurroundings. The heat given off by the system is the same amount of heat that is absorbed by the surroundings because the heat of the universe has to stay constant.
by LilyL1C
Fri Feb 15, 2019 10:17 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs and Enthalpy
Replies: 4
Views: 79

Re: Gibbs and Enthalpy

Gibbs free energy measures the amount of energy that is free after a reaction, basically the energy left that is able to do work. Delta H measures the amount of energy that was taken in by a reaction so that the reaction could run, or the amount of energy that the reaction released when it ran.
by LilyL1C
Fri Feb 15, 2019 10:14 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Gibbs free energy
Replies: 7
Views: 118

Re: Gibbs free energy

You can find Gibbs Free Energy by using the equation deltaG = deltaH - T(deltaS). And a reaction will be spontaneous if deltaG is a negative value, which can happen in three ways: 1. delta H is a small, positive number and delta S is a large positive number. This would give you deltaG = positive# - ...
by LilyL1C
Fri Feb 01, 2019 8:36 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Different Kinds of Symptoms
Replies: 6
Views: 114

Re: Different Kinds of Symptoms

An open system is one that can exchange matter and energy with its surroundings. So for example, a beaker with some hot water in it is an example of an open system because the system is not insulated and the water will eventually cool down and evaporate. A closed system is one that can only exchange...
by LilyL1C
Fri Feb 01, 2019 8:31 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 3 methods for enthalpy calculation
Replies: 10
Views: 191

Re: 3 methods for enthalpy calculation

It really depends on the given conditions in the question. If they give you the values for bond enthalpy, use bond enthalpy; if they give you the values for combustion, use combustion, etc. But keep in mind that bond enthalpy is the least accurate because those values are averages.
by LilyL1C
Fri Feb 01, 2019 8:28 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: 1st law of thermodynamics
Replies: 7
Views: 146

Re: 1st law of thermodynamics

The first law of thermodynamics says that matter cannot be created or destroyed, and that the internal energy of an isolated system is constant. The universe is an example of such a system because all the energy in the universe is conserved and cannot be lost or created. No matter what happens in th...
by LilyL1C
Fri Jan 25, 2019 8:09 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE problems
Replies: 5
Views: 119

Re: ICE problems

It depends on which way the reaction is going. If it is a forward reaction, then reactants are getting turned into products, so you would subtract the change from the reactants and add the change to the products. If it a reverse reaction, then the products are getting turned into reactants, so you w...
by LilyL1C
Fri Jan 25, 2019 8:03 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 3 Methods
Replies: 3
Views: 71

Re: 3 Methods

Bond enthalpies are the least accurate method because unless you are dealing with all diatomic elements, the values that you are using for delta H are averages, so these numbers will always be a little off. Therefore your final answer will also be a little off. Comparing this method to the other met...
by LilyL1C
Fri Jan 25, 2019 7:58 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Accurate and estimation of bond enthalpy
Replies: 3
Views: 72

Re: Accurate and estimation of bond enthalpy

There are only 7 diatomic molecules, and they are H2, N2, F2, O2, I2, Cl2, and Br2. And the bond energies of any other bond is an average because since it cannot be measured like those of diatomic molecules are. For example, to achieve this average for C-C, you take the energies of every single C-C ...
by LilyL1C
Wed Jan 16, 2019 8:35 pm
Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
Topic: Acid and Base Equilibria
Replies: 7
Views: 126

Re: Acid and Base Equilibria

Yes, that is correct. And the pH scale is set up so that 0 is acidic, 7 is neutral, and 14 is basic. So a weak acid's higher pH means that it is less acidic and more basic than the strong acid.
by LilyL1C
Wed Jan 16, 2019 7:18 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5I.19 7th edition
Replies: 1
Views: 48

Re: 5I.19 7th edition

The 60% is the amount of hydrogen gas that reacted in the reaction, in other words, your change, x. So once you set up your ICE table, you can write -x for H2, -x for I2, and +2x for HI. Then you can calculate x by multiplying the initial concentration of hydrogen gas. Once you have x, plug it in fo...
by LilyL1C
Wed Jan 16, 2019 7:01 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Approximation of x
Replies: 3
Views: 220

Re: Approximation of x

Yes, we can assume that x is negligible if the K value is less than 10^(-3), and today in class, Lavelle said that all weak acids will have a K value less than 10^(-3). So you can do it for all weak acids.
by LilyL1C
Fri Jan 11, 2019 8:14 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Calculating Equilibrium Concentrations when k < 10^-3
Replies: 2
Views: 61

Re: Calculating Equilibrium Concentrations when k < 10^-3

I believe that as long as x is smaller than 10^-3, you can just use the initial concentration as the equilibrium concentration. And you can use it in both quadratics and cubics.
by LilyL1C
Fri Jan 11, 2019 7:29 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Le Chatelier's Principle [ENDORSED]
Replies: 3
Views: 56

Re: Le Chatelier's Principle [ENDORSED]

So Le Chatelier's Principle basically means that once the reaction is at equilibrium, it wants to keep it's concentrations like it is at equilibrium forever. And whenever we do something to the equation, it will always try to undo whatever we did and go back to the concentrations it had at equilibri...
by LilyL1C
Fri Jan 11, 2019 6:44 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp vs Kc
Replies: 6
Views: 95

Re: Kp vs Kc

It really depends on the question. If the equation is comprised of only gases and they are asking you to find the equilibrium constant, then you should use Kp. But even if the equation only has gases, and they give you the concentrations of the compounds, it's easier to use Kc. You could still conve...

Go to advanced search