CHEMISTRY COMMUNITY

Brianna Bui 2J

Hi! Just to add on to the previous answer, Ionization energy (amount of energy needed to remove an electron) is a periodic trend. You can predict the ionization energy of one element to the next using the trends. Ionization energy increases from left to right across a period and decreases down a col...

Brianna Bui 2J

HI!

Just like O2, the oxidation number of O3 is 0

Brianna Bui 2J

An isolated system is not only no energy flow in or out of the system, but it also means that there is no transfer of matter in or out of the system. Thus an adiabatic system would follow the no energy transfer requirement of a system, but that doesn't necessarily mean that there is no transfer of m...

Brianna Bui 2J

Hi! Entropy increases when the volume increases because there is more space for the molecules to move and different ways they can collide. Basically, their arrangement becomes more random. Spontaneous reactions mean that they can occur without an input of energy, they just happen. The second law of ...

Brianna Bui 2J

An isolated system is one in which no energy and matter can be transferred. Thus, those who consider the universe to be an isolated system say it is because there is no matter or energy exchange with it's surroundings. It was mentioned in lecture that a truly isolated system would technically be imp...

Brianna Bui 2J

Hi!

I find that the best formula I like to use for phase changes are the ones with q. The ones that are q(phase change)=mass*enthalpy of fusion/vaporization.

Brianna Bui 2J

Well, the shortest answer to your second question is that it is actually technically impossible to have a perfectly isolated system in which both matter and energy cannot transfer through, so this actually does not occur naturally. However, some other examples of isolated systems (which again is deb...

Brianna Bui 2J

Hi!

They should be the same because to isolate k from lnk, you would multiply by e and that would give you the leftmost equation you listed. So the shortest answer is yes, you can use both and get the same answer. :)

Brianna Bui 2J

The Arrehenius Equation formula is as follows:
k=A(e^-Ea/RT)

In this formula, A is the frequency factor. A represents the the number of collisions with the correct rotation that allows the reaction to commence. Hope that helped!

Brianna Bui 2J

Hi! Here's my understanding of the two: Steady state: consider the the concentration of an equilibrium to be a constant value in a rate limiting step of a reaction (slow step). So, when you take the derivative, d[intermediate concentration]/dt which gives you the rate of change of concentration over...

Brianna Bui 2J

Hi! My first instinct is to tell you that since Ka is just the acid dissociation constant, it is the same as the K of the dissociation equation. So I'm not sure if there's more to the problem that is not in this picture (an overall balanced equation), but what I believe I would try to do (to make su...

Brianna Bui 2J

Hi! other people went into great detail :), but i find short supplemental summaries helpful too, so i offer the following: So you use H2O to balance oxygen atoms (add the H2O to the side opposite of the oxygen atoms). Electrons are used to balance charges (and are usually added to the side with the ...

Brianna Bui 2J

Hi! The equations I find helpful in thinking through these relationships are deltaG° = -RTIn (K) deltaG° = -nFE°cell E°cell = (deltaG°)/nF when K=1 (system is at equilibrium), delta G° and E°cell are equal to zero. For delta G, it is zero because K=1 and ln(K) = ln1=0. Since the lnK term is multipli...

Brianna Bui 2J

Hello! The shortest answer to your question is that you introduce water in a half reaction in order to balance the oxygen atoms. Like the others said, first you balance the non hydrogen and oxygen atoms. Then you balance the oxygen atoms by adding water to the opposite side. The method I choose to u...

Brianna Bui 2J

(Like so many people said lol) R depends on the units of pressure (and volume) in the problem. Because values of R are usually written with the units (V*P)/(mol*Temp-in Kelvin) the most common different values are thus (assuming V is in Liters): atmospheric pressure at sea level (atm) 0.082057338 L....

Brianna Bui 2J

Some other examples of extensive properties (dependent on the amount of substance present): volume, heat capacity (heat required is extensive), and mass Some other examples of intensive properties (not dependent on the amount of substance present): specific & molar heat capacities, density, temp...

Brianna Bui 2J

It is because steam releases more energy onto skin than hot liquid water. This is because steam had energy (heat) added to it, not only to raise it's temperature, but also to vaporize it. Hot liquid water of the same temperature has less energy because there was no energy put into a phase change. Th...

Brianna Bui 2J

Hi!

The change in surroundings always 0 because the final and initial entropies of the surroundings are equal. Thus their difference is zero. This is because energy cannot be added or taken from the surroundings; the entropy is inside the system and does not transfer to surroundings.

Brianna Bui 2J

No, by definition, an isolated system is purposefully insulated so that energy cannot flow in and out. ~~Technically~~ though, it was mentioned in a lecture that its impossible to completely prevent energy from flowing between systems and surroundings, but for this class, we just need to know: isola...

Brianna Bui 2J

Hi! When you are doing Hess's law for thermodynamic equations such as ∆H, you add the ∆H values. When having to increase the mole ratio of one reaction to match the overall equation, you multiply that constant to that reaction’s ∆H value. Meaning, if you double the mole ratio of an equation, make su...

Brianna Bui 2J

Entropy is the amount of disorder in a system. Changes in entropy are modeled delta S. A negative delta S value is actually indicative of an decrease in the disorder of the system/system becomes more ordered. A positive delta S means that the disorder of a system has increased from a reaction. Somet...

Brianna Bui 2J

Hi, During phase changes, the heat being added is use to break the hydrogen bonds of the water molecules (breaking bonds is endothermic/requires heat). So even though more heat is being added, that heat is not raising the temperature of the water. This is why the heating curve is flat during phase c...

Brianna Bui 2J

Hi! We are calculating how much the base deprotonated: how the concentration of hydroxide compares to the concentration of the original base. This is calculated by [OH^-]/[Initial Base] *100. Strong bases deprotonate completely and thus have a higher percentage than weaker bases. This concept is hel...

Brianna Bui 2J

Hi! Just wanted to add that it depends on how the change in pressure is created. If it is by pumping in an inert gas like He, there shouldn't be a change in the equilibrium because inert gases are not reactive. If the pressure change was due to a change in volume, like a piston chamber decreasing th...

Brianna Bui 2J

Hey! I'm not completely sure on this topic, but I did some additional research and here is what I found. a reversible process was defined as being able to be "turned back to such that both the system and the surroundings return to their original states, with no other change anywhere else in the...

Brianna Bui 2J

Hi! Enthalpy is commonly referred to as heat, but is also the energy stored in potential bonds. Change in enthalpy is written as delta H. Exothermic reactions result in a release in heat, so delta H is negative. Heat is released to the surroundings. Forming bonds results in a release of energy and i...

Brianna Bui 2J

That works! I also like to think about the components of the substance to try to determine if they are a strong acid/strong base. Some strong acids have a hydrogen paired with a halogen (with the exception of F as HF is a weak acid). Ex: HCl, HBr, HI Some strong bases have cations from period one (a...

Brianna Bui 2J

Hi, buffers tend to be weak acids and bases because their disassociation has both forward and reverse reactions. In other words, they do not completely ionize/disassociate, so there are still reactants in the solution once the reaction has reached equilibrium. This means that the reverse reaction ca...

Brianna Bui 2J

Are Kp and Kc constants? If not, how do we determine the value for them and is a specific variable preferred? Kp and Kc are both equilibrium constants. Kc is an equilibrium constant when the (molar) concentrations of the substances at equilibrium are used in the calculation. Kp is an equilibrium co...

Brianna Bui 2J

K is generally used to refer to an equilibrium constant Kc is an equilibrium constant when the concentrations of the substances at equilibrium are used in the calculation. Kp is an equilibrium constant when the partial pressures of the substances at equilibrium are used in the calculation. A small d...

Brianna Bui 2J

Hi, I'll just add a more visual example to go with the other person's very helpful reply. Example 1 When adding two reactions with different Kc values reaction 1: aA<-->cC Kc=x reaction 2: bB<-->dD Kc=y coupled reaction: aA+bB<-->cC+dD Kc=x*y _________________________________________________________...

Brianna Bui 2J

Hi! Q equals K when a reaction reaches equilibrium. This does not mean there is the same amount of products and reactants! It just means the rate of reaction of the forward and reverse reactions are equal. You can tell when a reaction has reached equilibrium when the concentrations of both the produ...

Brianna Bui 2J

Hi! Yes, the phases of the substances in the equation do affect how we calculate K, since we omit substances that are pure liquid and solid form in the equation to calculate K. So, if an equation is homogeneous gas (all reactants and products are gas) then you can include all reactants and products ...

Brianna Bui 2J

I like to just loop Shinunoga E-Wa and it becomes such relaxing background music for my brain while I work.

Brianna Bui 2J

Assuming you're talking about R in PV=nRT: R depends on the units of pressure (and volume) in the problem. Because values of R are written with the units (V*P)/(mol*Temp-in Kelvin) the most common different values are thus (assuming V is in Liters): Bar 8.3144598 × 10-2 L.bar.K-1.mol-1 Kilopascal (k...

Brianna Bui 2J

This huge dark chocolate candy bar from Trader Joes near campus. I really recommend for dark chocolate lovers, but they also have a milk chocolate version. It is literally a pound of chocolate and I love it so much :)

Brianna Bui 2J

Q: Why do the other elements call group 18 "the knights of the periodic table"?

A: Because they are the noble gases.

i'm sorry everyone :(

CHEMISTRY COMMUNITY

Search found 37 matches

Re: Ionization energy and enthalpy of ionization

Re: oxidation number

Re: Week 5- Isolated system: Adiabatic

Re: Week 5- Volume and Entropy

Re: Week 4- The Universe is an Isolated System?

Re: Week 3- Enthalpy methods and phase changes

Re: Week 4- Isolated Systems

Re: Versions of Arrhenius Equation

Re: Arrhenius Equation Frequency Factor

Re: Steady State Approximation and Pre-Equilibrium

Re: UA session worksheet question

Re: Half Reactions

Re: E cell, K and Delta G

Re: Adding in H2O when balancing redox reactions

Re: Value of R

Re: Entropy

Re: Why does heat cause a worse burn than boiling water at the same temp?

Re: irreversible process

Re: Isolated System

Re: Hess's Law for Thermodynamics

Re: Entropy

Re: Heating Curve for Water

Re: Percentage protonated

Re: Effect of pressure

Re: Reversible process

Re: Enthalpy

Re: Strong Acids and Bases

Re: Buffers

Re: Kp vs Kc

Re: K vs KC

Re: Adding equations to find Kc

Re: When Q = K

Re: Homogeneous and Heterogeneous

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