CHEMISTRY COMMUNITY

Alex Ottersbach

If k is less than 10^-3 it is ok to approximate. This is to say that the change of x would be so small it is irrelevant but not that there is no change. You would not put zero in for x but rather ignore the change of x in your (presumably) denominator. You can check if your approximation was okay by...

Alex Ottersbach

Do the math paying close attention to the units being used. Everything needs to carefully cancel out in order for your answer to be valid. if one of the gas constants has a unit not given to you and not being asked for, it is the wrong one!

Alex Ottersbach

Adding gas to a system to change the pressure does not change partial pressures and therefore has no affect. Decreasing the volume however by shrinking the container (compression) would shift the equilibrium to the side with less moles.

Alex Ottersbach

This very much depends on the information given in the question. Sometimes the question might directly give you this value. Oftentimes you will need to simply find the moles by dividing the mass by the grams of one mole of something. Other times it might give you other information that would require...

Alex Ottersbach

Which one you use relies on the information given. Delta H is just your normal change in enthalpy and is very often the subject of a question. It takes very little into account. Delta H standard is the change in enthalpy only under standard conditions (pressure and temp). The delta h of formation is...

Alex Ottersbach

Under constant pressure delta H and q are equal to one another. U=q+w and therefore it can depend on whether w or q are equal to one another. At equilibrium neither qualities would necessarily be equal to zero. I think the question gave a little more information. It might have been that it stated on...

Alex Ottersbach

The question should be relatively clear on which of the two it is asking about. Both will be about the change in their values but enthalpy is the heat or energy of a system and entropy is the disorder or amount of positions something can be in. Most questions will use the two terms or will show delt...

Alex Ottersbach

Work will always be zero in an isolated system because an isolated system cannot be changed. No exchange of mass or energy can be done with an isolated system so no work can be done on one or by one.

Alex Ottersbach

Bond enthalpies by definition are the energy required to break a specific bond. A negative enthalpy would be the release of energy and is not the same thing. However, the amount of energy required to break a bond is the same amount of energy required to create that bond and you can therefore just fl...

Alex Ottersbach

I'm not entirely sure what you mean by the greatest. If you mean how much energy they require, then of course sublimation requires much more energy than vaporization because it would include the necessary energy for both fusion and vaporization. It is two phase changes at once effectively. There is ...

Alex Ottersbach

The salt bridge attempts to maintain a neutrality of charges and prevents a build up of negative or positive charges in one side of lets say a galvanic cell. With electrons constantly being sent from one side to another, there would obviously be too many negative charges on the receiving end and too...

Alex Ottersbach

The steps remain largely the same. You have to add water to the equation regardless but to balance out the extra hydrogens you add H+ ions to acidic solutions and OH- ions to basic solutions. Other than that everything else doesn't change based on it being acidic or basic.

Alex Ottersbach

That is correct. The higher the activation energy the more susceptible a reaction is to temperature changes. Higher temperatures will affect something with a higher activation energy more than something with a lower activation energy.

Alex Ottersbach

The graphs would each be shown with a straight line as graphing one part of any order against time would always result in linearity.

Alex Ottersbach

Enzymes are not directly part of the rate as they are not used up. They are similar to intermediates in that they are outside necessary factors to a reaction occurring.

Alex Ottersbach

Memorizing them is in your best interests but as a general rule of thumb I would say that zero order reactions are normally the simplest and most straight forward. First order reactions are more difficult to guess and should probably be memorized but second order reactions typically square something...

Alex Ottersbach

Enzymes are proteins that catalyze a reaction to make them occur faster. They can also regulate when and how reactions occur. They lower the activation energy of reactions so they can occur more frequently and quicker. Occasionally reactions would be impossible without enzymes but often they make re...

Alex Ottersbach

You did the rest of this question all correct you just missed the conversion from kj to joules to match the rate constant. Your answer will end up a very large number. Just make sure to do the same thing for both temperatures.

Alex Ottersbach

The rate of formation is determined by the slow step giving rate=l[I-][HClO] The forward and reverse rates can be set equal to one another because the reaction is at equilibrium. k[ClO-]=k[HClO][OH-]. Then we can solve for HClO and substitute that answer into our original rate equation. We then end ...

Alex Ottersbach

You would need the delta G value to be able to determine if a reaction is spontaneous. Just having the delta h value isn't enough because its spontaneity would depend on delta S as well, or the entropy value. The delta U would also not be able to tell you if a reaction is spontaneous or not.

Alex Ottersbach

Hello, entropy is the degree of disorder of something. When we look at it in this class it normally refers to a reaction and the change in entropy. To better understand this, when a gas is highly pressurized the particles are moving faster and there is more disorder, hence higher entropy. It can als...

Alex Ottersbach

reactants are negative because their concentration will be decreasing whereas products will be positive because theirs is increasing

Alex Ottersbach

To understand the orders you must think of the number of species interacting at once. The rate equation for zero order is rate=k. We are trying ot find our answer in concentration over time. A common unit for that is molarity/seconds which is what we will try and solve for and put in as our rate. Fo...

Alex Ottersbach

it is important to understand that the value being positive means that something is endothermic and negative meaning it is exothermic. Questions given will often give the value and therefore there is nothing to figure out. other times it will refer to bond enthalpy values and ask you to find the tot...

Alex Ottersbach

Bond enthalpy is the energy required to break a bond and is therefore always positive when seen in charts. However, this value tells you both the energy required to break and create a bond as they are simply the inverse of one another. Negative bond enthalpy value is what is required to create the s...

Alex Ottersbach

It always requires an input of heat and energy to break a bond. This would therefore not be spontaneous and must be endergonic and exothermic. Creating a bond releases heat and is therefore spontaneous making it exothermic.

Alex Ottersbach

Delta U is the change in the internal energy of a system. This can be added and does not depend on any path, therefore it is a state function.

Alex Ottersbach

The sheet of constants includes that!

Alex Ottersbach

Bond enthalpy values are always positive because it always requires an input of energy to break a bond, which is effectively what a bond enthalpy value is. It is technically the amount of energy stored in the bond and it requires as much to break it.

Alex Ottersbach

Spontaneity refers to if a reaction can occur on it's own, without an input of energy. This could be called a reaction occurring spontaneously. Reactions that can occur spontaneously have a negative delta G value and release energy. Reactions that do not occur spontaneously require an input of energ...

Alex Ottersbach

Hello. Utilizing the VSEPR rules such as those in this image will help you.

Alex Ottersbach

Hello. Every substance is different and it also depends on what phase change is being done. Q=mL is the formula for heat released and L is a "latent heat coefficient." Every substance would undergo phase change at a set specific temperature so naturally the heat released or absorbed is dif...

Alex Ottersbach

how many questions are on the midterm? which lectures exactly will be covered?

Alex Ottersbach

if you click on your name you can find all your previous posts

Alex Ottersbach

yes you can download it on the website! We can access it for a few years if i recall correctly.

Alex Ottersbach

There is a section under 14A. There are various videos and links for acids and bases in 14B though.

Alex Ottersbach

The same account works just fine!

Alex Ottersbach

Is there anyway we can access lecture slides?

CHEMISTRY COMMUNITY

Search found 38 matches

Re: when to approximate

Re: Gas constant R

Re: Le chatelier's principle regarding pressure

Re: work done on a system

Re: week3- Enthalpy of formation vs standard enthalpy

Re: Is deltaH > deltaU at equilibtrium?

Re: Entropy vs. Enthalpy

Re: Isolated Systems

Re: Bond Enthalpies

Re: Phase Changes

Re: Salt Bridge Role

Re: Balancing in Acidic vs Basic

Re: Ea Dependence

Re: Graphs

Re: Rate law

Re: Orders in Equations

Re: Enzymes and biological kinetics

Re: Achieve Week 8-10 #20

Re: Achieve Week 8-10: Chemical Kinetics #13

Re: Spontaneous Reaction

Re: What is Entropy?

Re: Achieve Weeks 8-10, #1

Re: Achieve Week 10 #4

Re: Reaction Enthalpy pos/neg signs

Re: Bond Enthalpy

Re: Forming and breaking bonds

Re: delta U

Re: Entropy

Re: Bond enthalpy value

Re: spontaneity

Re: Nonlinear and Linear Molecules

Re: phase changes

Re: Midterm

Re: How to find my posts

Re: Textbook Inquiry [ENDORSED]

Re: Acids and Bases

Re: New account for Chem 14B?

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