CHEMISTRY COMMUNITY

Litsa Dimit 1D

The forward reaction would be spontaneous because in the equation, G= -RTlnK, you would want the G to be negative, so in order for you to do this the K must be greater than 1. If it was a negative number it would yield a positive G, and it would not be spontaneous anymore.

Litsa Dimit 1D

Rate constant (k) can not be negative. Rates are always positive, the only way there could be a “negative” rate is if you are possibly looking at the slope decreasing, however the rate is still increasing thus making it positive.

Litsa Dimit 1D

You are correct, the more the reduction potential value the stronger the oxidizing agent. This is because the reduction potential has more affinity towards electrons which will make it more likely to become reduced. An oxidizing agent is an electron acceptor, it oxidizes other substances which cause...

Litsa Dimit 1D

A complex ion contains a central metal ion and is covalently bonded to two or more molecules (or ions). They are able to undergo reduction-oxidation reactions. For example MnO4^- reacts with Cl- to form Mn^2+ and Cl2.

Litsa Dimit 1D

The most simply way to know when an equation was either oxidized or reduced is to look at the oxidation number. If there was an increase this refers to oxidation however a decrease will be reduction. Also keep in mind that the atom that is oxidized will be the reducing agent which means that the che...

Litsa Dimit 1D

If a half-reaction needs to be multiplied, you do not need to multiply the value of E* because the standard reductional potential is an intensive property which indicates that it does not depend how many times a reaction can occur. We want to multiply the entire reaction to balance it which is not c...

Litsa Dimit 1D

For acidic solutions, make sure to divide into half reactions and balance like normal (the ones that are not H or O). To balance the O atoms, you must add H2O and to balance the H atoms, you must add H+ to both your products and reactants. After this step, you should balance the charges by adding el...

Litsa Dimit 1D

N is the number of electrons that are transferred in a redox reaction. It is the moles of electrons. You need to make sure the reaction is balanced as well. For example if there were 5 electrons transferred (5 e-) then n would be equal to 5.

Litsa Dimit 1D

We want a positive rate, so if we put a negative sign infront of the variables -d[R]/dt, then we could get a “+” value. The reason why we do this is because since the reactants are decreasing, the rate would have to be negative, so to undo this we add a negative to the equation. The rate reaction is...

Litsa Dimit 1D

Voltaic cells use the energy from a spontaneous reaction to do electrical work while electrolytic cells use electrical work as an energy source to a reaction in the opposite direction. For a voltaic, the anode is negative and cathode is positive, this ie because the reaction is proceeding forward wi...

Litsa Dimit 1D

The anode is the positive side, usually and it will be on the left side while the cathode is typically the negative side and is placed on the right. Reduction occurs in the cathode and is in the right half-cell, oxidation occurs at the anode in the left half-cell. To tell which one is positive and n...

Litsa Dimit 1D

If a reaction is 0 order this means that the units will be M s^-1 (m/s), if it is 1st order the units will be s^-1 (1/s), and if its second order it will be M^-1 S^-1 1/(ms). The units of the rate constant depend on the reaction order.

Litsa Dimit 1D

Detla T= 0 which means that this system is undergoing an isothermal reaction.

Litsa Dimit 1D

A double line separates the anode half reaction from the cathode half reaction which ultimately represents a salt bridge. Ions are able to flow through.

Litsa Dimit 1D

As temperature is increasing, entropy will increase as well because the disorder will be greater. As volume increases, entropy also increases since there will be more space.

Litsa Dimit 1D

When work is being done ON the system it is positive and when work is done BY the system it is negative.

Litsa Dimit 1D

If you use PV=nRT you are using 0.08206 and If it asks for your answer in J or kJ you need to use 8.314.

Litsa Dimit 1D

An adiabatic system is considered a closed system. Energy is not transferred as heat but it can still change if it is transferred to or from the system as work. This is why (change in) U=w because q is zero.

Litsa Dimit 1D

Calculating work done by the surroundings on a system would use w = - ∫(Pdv). P refers to the applied external pressure and is proportional to V for constants n and t in P= (nRT)/V.

Litsa Dimit 1D

You add the enthalpies which is the (change in H) values. When you are reversing a reaction to match the equation, you must multiply the enthalpy by which the factor was multiplied by.

Litsa Dimit 1D

If you are changing pressure, the system will need to go back to its equilibrium point. The system will work to adapting to this change in pressure thus leading to where there is less moles in the reaction.

Litsa Dimit 1D

The ice pack becomes cold rather than warm because it is endothermic; heat is entering the reaction which the surroundings are losing heat which causes drop in temperature.

Litsa Dimit 1D

They will be posted tomorrow and midterm questions will be discussed in discussion this week!

Litsa Dimit 1D

The approximation obtained by removing X will be accurate if X represents less than 5% of the initial concentration. If K is bigger than 10^-3, we must use the quadratic equation to solve the problem since we cannot ignore X. For example, if the equation is (x^2)/(0.40-x) = K then you can just do (x...

Litsa Dimit 1D

A reaction is exothermic and will have a negative enthalpy if it releases more energy than it takes in. Consider the exothermic as having been "subtracted" from the reaction. A reaction is endothermic, and its enthalpy will be positive if it absorbs or utilizes more energy than it generates.

Litsa Dimit 1D

A property unrelated to how a substance was made is called a state property. Some examples are enthalpy, pressure, volume, and internal energy.

Litsa Dimit 1D

This is how I worked backwards with this problem. pOH = 14 - pH, once you get your value you need to find [OH-] which will be 10^-pOH. Once you have these two values you will need to find [B] using Kb. To find [B] you need to do [OH-]^2/pOH. Now to get the percentage protonated, you need to do [OH]/...

Litsa Dimit 1D

The Q value tells you when a reaction is at equilibrium because it must be equivalent to K. Reactions can reach equilibrium, the double arrow does not tell you if it does it is there to tell you that the reaction is reversible. If K is greatest than Q, the reaction will proceed forward, if K is less...

Litsa Dimit 1D

A homogenous equilibrium is when both the reactants and the products are within the same phase, while heterogenous equilibrium is when at least one of the substances, which can be the reactants or products, are in a different phase. For example one substance can be gaseous while the other is solid. ...

Litsa Dimit 1D

Since the numerator and the denominator equations are squared, you can take the value of Kc and square both sides in order to get rid of any "hard work" by doing tedious quadratic formula work. Then you can solve like a normal equation and divide the side with x.

Litsa Dimit 1D

The deadline is every week on Sunday night.

Litsa Dimit 1D

Personally, I believe your way is more correct and I would do it that way instead. I think the textbook wanted you to be able to differentiate between the partial pressures. Brackets or paranthesis, they do the same thing.

Litsa Dimit 1D

K is the equilibrium constant. Since we want to specify, Kp is with partial pressure while Kc is when you are given the concentration. It just helps you to know what you are doing in your work.

Litsa Dimit 1D

Ice tables can be used for partial pressure because the equilibrium constant can be used in order to find the partial pressure.

Litsa Dimit 1D

Electrons contribute only to the atom in the molecule but the bonds are shared between the electrons.

Litsa Dimit 1D

H2O is bent because it has AXE2 and the bond angle is 104.5!

Litsa Dimit 1D

Ampotheric is able to react as both an acid or a base, so it can accept and donate electrons.

Litsa Dimit 1D

I am pretty sure that Dr. Lavelle checks chemistry community posts at the end of the quarter so you could do all 50 if you wanted right now! Just as long as you have the amount at the end.

Litsa Dimit 1D

On the syllabus, he has everything that we should know.

Litsa Dimit 1D

Thank you, I will be coming back to this!

Litsa Dimit 1D

I don't think there is any extra credit because Lavelle already gives us respondus questions for our exams and achieve assignments.

Litsa Dimit 1D

Yes! I would love to be in a study group for the final!

Litsa Dimit 1D

I think everyone needs to do in person unless there's a medical emergency or your primarily on zoom!

Litsa Dimit 1D

I created my own chart with the geometry, shape, and bond angles. I coupled them up in groups and used the generic formula, AXE to help me!

Litsa Dimit 1D

You need to use VSEPR and categorize the atoms in the molecule into different groups, for example, C-C-C or H-C-H to see what their geometry is and then figure out the bond angle!

Litsa Dimit 1D

It will be cumulative, so everything we have learned in the quarter!

Litsa Dimit 1D

I always find myself going back to Khan academy!

Litsa Dimit 1D

It just helps the questions ask us to use angstrom units since its 10^-10 meters. It is a conversion, also on the cheat sheet!

Litsa Dimit 1D

Tetrahedral = 109.5 degrees

Litsa Dimit 1D

Trigonal pyramidal has 1 lone pair while t-shape has two lone pairs connected to it also the bond angles are different.

Litsa Dimit 1D

Elements that are in period 3, so S, Cl, Al are all examples!

Litsa Dimit 1D

A lewis acid is typically accepting electrons, so example OH- F- while a lewis base donates electrons, H+,K+

Litsa Dimit 1D

Sigma bonds are a single bond, however pi bonds are more than just one bond. So every structure has a sigma bond but if it were to be a double bond, it would have 1 sigma 1 pi.

Litsa Dimit 1D

The central atom is typically the most least electronegative!

Litsa Dimit 1D

Formal charge is usually just one atom in a molecule, and we can calculate that with the equation FC= v(# of balance electrons)-L(lone pairs)-(s)/2 while oxidation states is how much electrons the atom loses or gains.

Litsa Dimit 1D

VSEPR stands for Valence shell electron pair repulsion theory, which is a model that allows for us to predict molecular geometry and the shape of molecules.

Litsa Dimit 1D

Not to worry! It probably will be added shortly, just attempt again when Respondus is up.

Litsa Dimit 1D

Chemistry Community points are added up at the end of the quarter, so you could write all 50 right now if you wanted to.

Litsa Dimit 1D

Typically the atoms have the same formal charge depending on their number of electrons!

Litsa Dimit 1D

Periods are horizontal, so the first row is period 1 second is 2 and so on. The groups are vertical and I associate them with metals, gases, liquids!

Litsa Dimit 1D

Lone pairs are the dots! So the ones that surround the atom. It basically means they are not bonded together.

Litsa Dimit 1D

It is going to cover ionization energy and trends on periodic table, also chemical bonds. Everything we have learned after the quantum world!

Litsa Dimit 1D

Only write it if it says to! It is also good practice to write the formal charges for each!

Litsa Dimit 1D

Yes, we would list London dispersion forces because as we know they are present in all molecules but it is more when it comes to large atoms.

Litsa Dimit 1D

It is helpful to know where it came from and how to derive it, but it is not necessary to memorize!

Litsa Dimit 1D

It would have two significant sig figs because the leading zeros do not count, only if it is trailing.

Litsa Dimit 1D

I haven't taken a chemistry course since sophomore year and I am a freshman right now! What has helped me in his course is definitely going over the fundamentals with Lavelle's recorded lectures or even online study tools! Mastering the basics really helps.

Litsa Dimit 1D

It will probably be out this week! I think we are going over the questions in lecture or discussion too!

Litsa Dimit 1D

I have heard that Lavelle curves, but I am not too sure about the midterm since it is out of 15, and someone may have gotten a 100% not too sure!

Litsa Dimit 1D

Electrons have a negative charge which means they move away from other electrons, while photons are units of the electromagnetic wave. Associate photons with visible light and that help understand the difference too!

Litsa Dimit 1D

Lately, I have been rewatching the lecture and going over textbook problems. I also make sure to review what we do in discussions, like the questions that they ask us to do, it has been really helpful in understanding the material. Also, I like to go over the post-module assessments!

Litsa Dimit 1D

Hi! It's probably due before the midterm and I do not think it is a grade but make sure to do it because the exact question that is on the respondus will be on the midterm which is worth 4 points.

Litsa Dimit 1D

Hi! I did not take AP Chemistry either and what I found what helped me most was going over all the fundamentals and making sure I was able to master it. Then I would rewatch the lectures and do some textbook problems!

Litsa Dimit 1D

Usually whenever I balance equations, I always start on the left and match it up to the right so reactants first! It makes it easier when trying to solve it.

Litsa Dimit 1D

When you balance equations you must multiply in order to get a whole number because coefficients cannot contain fractions!

Litsa Dimit 1D

I am in Rieber Terrace and would also love to have study sessions!

Litsa Dimit 1D

You should have a general understanding, not complete memorization but the basics of UV!

Litsa Dimit 1D

In midterm 1, it is going to be based on the fundamentals of high school chemistry from week 1 and then the quantum world topics!

Litsa Dimit 1D

I feel like if we were to round to 6.3 it would yield a completely different answer than if we were to use the more accurate 6.626!

Litsa Dimit 1D

To solve this problem, I took the mass of 2-butanone which was 0.60 mL and then multiplied it by 0.81 g/mL which was the density. I got 0.486 g. Once I found that I took the molar mass of 2-butanone which is 72.11 g per mole and the molar mass of the product is 116.2 g per mol. Once I have all of my...

Litsa Dimit 1D

There are steps to finding the limiting reactant
1. Identify the reactants and products
2. Write a balanced equation
3. Calculate the Molar Mass of each reactant and product
4. Convert known masses to moles
5. Compare calculated moles to required moles to determine the limiting reactant.

Litsa Dimit 1D

I was so confused about this too! I thought we have weekly homework, but it is just whenever we finish the unit so that is why our homework was based on the fundamentals of high school chemistry!

Litsa Dimit 1D

You can use any gram sample it's just 100 is the easiest and better for you to work out the problem! It can be any!

Litsa Dimit 1D

Lambda represents the wavelength of any wave!!

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