Search found 29 matches

by Phan Tran 1K
Fri Mar 15, 2019 11:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Ka Kb = Kw
Replies: 5
Views: 37

Re: Ka Kb = Kw

The Ka/Kb can also help you find the concentrations of H+ of OH- ions depending on whether the reaction is acidic or basic, which can then help you find pH.
by Phan Tran 1K
Fri Mar 15, 2019 11:21 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: 15.69 6th Edition
Replies: 3
Views: 22

Re: 15.69 6th Edition

Essentially, the question is telling you that there's a k before the catalyst was added, let's call it k1, and a k after, k2. 1000k1=k2. From here, you can plug in the Arrhenius equation and the givens in order to find the original activation energy. There's a confusing part where you have to take e...
by Phan Tran 1K
Fri Mar 08, 2019 2:05 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Units of k
Replies: 4
Views: 40

Re: Units of k

K's unit changes depending on the order of the reaction because the reaction rate will always have to be some variation of M/s, and k compensates for the extra M's that gets added to the number when the reaction goes up in order.
by Phan Tran 1K
Fri Mar 08, 2019 2:02 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Water in a cell diagram
Replies: 5
Views: 47

Re: Water in a cell diagram

I think you do include water if it's not in liquid phase and if the H or O is one of the things being oxidized/reduced (this is rare but can happen), although I'm not really sure.
by Phan Tran 1K
Fri Mar 08, 2019 1:58 pm
Forum: General Rate Laws
Topic: 15.1
Replies: 3
Views: 26

Re: 15.1

They're basically asking you to give the ratio of N2 to H2, NH3 to H2, and NH3 to N2
by Phan Tran 1K
Fri Mar 01, 2019 6:21 pm
Forum: Balancing Redox Reactions
Topic: Half Reactions in a Basic Solution
Replies: 4
Views: 39

Re: Half Reactions in a Basic Solution

First, balance everything but Hydrogen and electrons. Then write down how many Hydrogens you need to balance the equation on the side that needs the Hydrogens. Then replace the Hydrogens with H2O molecules and add the same number of OH- molecules to the opposite side of the equation. In effect, this...
by Phan Tran 1K
Fri Mar 01, 2019 6:17 pm
Forum: Balancing Redox Reactions
Topic: Oxidation State
Replies: 4
Views: 27

Re: Oxidation State

An fast way to quickly identify what elements in a reaction could be being oxidized is to pinpoint anything that is not oxygen or hydrogen, since it is really rare for these two to have their oxidation numbers change. This usually leaves only two elements you have to calculate the oxidation numbers ...
by Phan Tran 1K
Fri Mar 01, 2019 6:07 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagrams (Using Platinum)
Replies: 10
Views: 51

Re: Cell Diagrams (Using Platinum)

We use platinum in a cell diagram when either the cathode or the anode lacks a solid that can be used to conduct electrons from one side of the beaker to the other. This is because platinum is inert and will not react with anything else in the reaction.
by Phan Tran 1K
Thu Feb 21, 2019 5:25 pm
Forum: Balancing Redox Reactions
Topic: Oxidation States
Replies: 10
Views: 62

Re: Oxidation States

The best way to find the oxidation state of a transition metal is to use the oxidation states of the other molecules in the compound witht he transition metal.
by Phan Tran 1K
Thu Feb 21, 2019 5:13 pm
Forum: Balancing Redox Reactions
Topic: Oxidation States
Replies: 2
Views: 23

Re: Oxidation States

There are a few rules that I memorized when assigning oxidation numbers, but they're fairly complicated 1.) Group 1 elements are always +1, Group 2 elements are always +2 2.) The oxidation numbers have to equal the total charge of the ion or molecule 3.) Hydrogen is +1 unless it is bonded to a metal...
by Phan Tran 1K
Thu Feb 21, 2019 5:08 pm
Forum: Balancing Redox Reactions
Topic: problem 14.1 6th edition
Replies: 1
Views: 15

Re: problem 14.1 6th edition

What I tried doing is to have H+ ions in the oxidation equation too. When I tried this I got C2H5OH ---> 6e- +C2H4O + 2H+
The problem with this is that even though the atoms add up, it doesn't balance the charges out in the equations, and I can't figure that part out.
by Phan Tran 1K
Thu Feb 14, 2019 10:27 pm
Forum: Calculating Work of Expansion
Topic: S=0
Replies: 12
Views: 109

Re: S=0

I think it's deltaS that can be zero. Not too sure if S itself can be zero, maybe at the hypothetical subzero?
by Phan Tran 1K
Tue Feb 12, 2019 2:15 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Application of Standard Enthalpy of Formation
Replies: 1
Views: 21

Application of Standard Enthalpy of Formation

I'm working through problem 8.99 in the 6th edition and I'm confused about how to apply finding the enthalpy of formation. The problem is long, and parred down to the relevant information it reads: A technician carries out the reaction 2 SO2(g) + O2(g) S 2 SO3(g) at 25 C and 1.00 atm in a constant-p...
by Phan Tran 1K
Thu Feb 07, 2019 6:26 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4.15 (7th edition)
Replies: 2
Views: 37

Re: 4.15 (7th edition)

For reaction enthalpies of combustion, its products-reactants, while it is the other way around for reaction enthalpies of formation. I just kinda memorize this.
by Phan Tran 1K
Thu Feb 07, 2019 6:22 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units
Replies: 2
Views: 30

Re: Units

Some problems will give you the amount of a substance and ask how much heat it gives off, and this is when J/mol comes into play. Other than that I don't think it matters if they're just asking for enthalpy.
by Phan Tran 1K
Thu Feb 07, 2019 6:20 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 4D7
Replies: 2
Views: 22

Re: 4D7

-PΔV = -ΔnRT is used to calculate w, which can be calculated using the equation w=-P*ΔV. You need to calculate w in order to calculate ΔU. I don't have the seventh edition, so is there anymore information that the book gives you? Like whether the reaction is reversible or irreversible, or whether T/...
by Phan Tran 1K
Thu Jan 31, 2019 9:10 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Studying gases
Replies: 2
Views: 43

Re: Studying gases

If it's a work problem, we're probably going to be dealing with gases. Heat problems, however, can have things in basically any state. There's a ton of homework problems, for example, that involve heating a piece of solid metal.
by Phan Tran 1K
Thu Jan 31, 2019 9:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Extensive
Replies: 4
Views: 48

Re: Extensive

A good way to remember the difference between extensive and state property is that the distance between your house and the supermarket is a state property; no matter how you get to the supermarket, that distance will always be the same, it's the state the distance will always be in. The path you tak...
by Phan Tran 1K
Thu Jan 31, 2019 9:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Extensive
Replies: 4
Views: 48

Re: Extensive

A good way to remember the difference between extensive and state property is that the distance between your house and the supermarket is a state property; no matter how you get to the supermarket, that distance will always be the same, it's the state the distance will always be in. The path you tak...
by Phan Tran 1K
Thu Jan 31, 2019 9:02 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Piston Problem in class
Replies: 2
Views: 49

Re: Piston Problem in class

The external pressure in the equation is really just the normal pressure outside of the system. When work is done by the system and pushes the piston up, this displaces the particles on the other side of the piston and thus results in the energy change. The external pressure changes so little when t...
by Phan Tran 1K
Fri Jan 25, 2019 1:44 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ignoring x
Replies: 10
Views: 94

Re: ignoring x

You can also check for this by finding the percent protonization by taking the concentration you get and dividing it bby the original concentration of your acid/base. If it's less than 5% then treating x as being so small that it is insignificant is valid.
by Phan Tran 1K
Fri Jan 25, 2019 1:41 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: autoprotolysis on Test 1?
Replies: 2
Views: 27

Re: autoprotolysis on Test 1?

Solving autoprotolysis should be the same as other weak acids/bases questions, using an ICE table and a pKa/pKb of 10^-7.
by Phan Tran 1K
Fri Jan 25, 2019 1:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium Favoring
Replies: 3
Views: 51

Re: Equilibrium Favoring

A reaction favoring either side of an equation is really just saying will the reaction proceed in the forwards or the backwards direction. You know this by calculating Q and then comparing it to K. Since in these quotients are a fraction with products on the top and reactants on the bottom, Q being ...
by Phan Tran 1K
Thu Jan 17, 2019 7:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Conjugate base
Replies: 7
Views: 66

Re: Conjugate base

If the reaction is in water, then whatever molecule that isn't the hydronium or hydroxide ion is the conjugate acid/base, depending on whether the molecule before the reaction is an acid or a base. Acids have conjugate bases and bases have conjugate acids.
by Phan Tran 1K
Thu Jan 17, 2019 7:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: How temperature affects K
Replies: 4
Views: 38

Re: How temperature affects K

Don't quote me on this, but I vaguely recall from high school chemistry that temperature measures the activity level of the particles in a substance while heat measures the energy they give off. I'm probably wrong since my memory is shoddy, and I'm sure we'll learn about this more in detail later on...
by Phan Tran 1K
Thu Jan 17, 2019 7:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Tables [ENDORSED]
Replies: 11
Views: 89

Re: ICE Tables [ENDORSED]

If you really want to be sure you can always just check the percent ionization after you solve the problem. If the concentration of the conjugate base/acid divided by the initial concentration of the acid/base is less than 5%, then you're good.
by Phan Tran 1K
Thu Jan 10, 2019 5:40 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert gases
Replies: 4
Views: 240

Re: Inert gases

Adding inert gases will only affect the equilibrium if the reaction is in a closed system. They add more particles, which increases the overall pressure and affects the other gases's partial pressure.
by Phan Tran 1K
Thu Jan 10, 2019 5:36 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: compression vs pressure
Replies: 6
Views: 240

Re: compression vs pressure

Wait, if compression changes which side of the equation is favored, would that eventually change the Kc too, since Kc tells you which side of the reaction is favored? I'm not really sure, can someone clarify?
by Phan Tran 1K
Thu Jan 10, 2019 5:32 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Effect of water
Replies: 2
Views: 227

Re: Effect of water

Keep in mind that aqueous substances are used in the equilibrium constant, but not liquid substances.

To add on, think of adding more liquid to a system with an aqueous substance like increasing the volume of a gaseous substance. It decreases the concentration of aqueous substances and affects Kc

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