CHEMISTRY COMMUNITY

Brittney Hun 2C

You put the concentration you got from approximated the concentrations in the equilibrium values (from an ICE table) over the original concentration that's given and if it is less than 5% the approximation is sound, then if not then you have to use the quadratic formula to find the values.

Brittney Hun 2C

They should give something that remains constant because that is the method being employed.

Brittney Hun 2C

How can we find [NO] if the concentration of [NO2] is not given to us? Since it is included in the k equation and we are given every other value.

Brittney Hun 2C

If the Enaught is always zero in a concentration cell, then will the Gibbs free energy also be zero?

Brittney Hun 2C

Will Ecell increase if the size of the anode metal is increased? Does the metal have anything to do with it? And will Ecell increase if a substance is added to the cathode side?

Brittney Hun 2C

Yes! You would use the log properties to rearrange it depending on what you want to solve for.

Brittney Hun 2C

First, convert the grams of N2O5 to mols and divide by the liters to get the molarity. You should get 0.0426M and then you just multiply it by the rate to get the second order reaction.

Brittney Hun 2C

You would use it to find the equilibrium constant, k.

Brittney Hun 2C

The solution for problem 7A.15 states that experiment [C] is independent of the rate. The problem proceeds to disregard the elements of reaction C as a valid comparison to find the rate, why is this?

Brittney Hun 2C

Does anyone know why we don't need an inert solid for the Au even though they are the same element?

Brittney Hun 2C

I understand why we put the solid Ni onto the cathode side of the cell diagram, but am still a little confused as to why the OH- is not on the cathode side even though it is in the half reaction.

Brittney Hun 2C

How do we know that Ag is both the oxidizing and reducing agent? Doesn't Br go from Br-(oxidation of -1) to AgBr (which has an oxidation of 0)?

Brittney Hun 2C

I am a little confused what the question is asking. It asks whether or not the metal ion or water will be reduced at the cathode or not? Doesn't everything get reduced at the cathode?

Brittney Hun 2C

So how does the charge of cl go from 0 to -1, don't both the cl2 have an oxidation number of 0?

Brittney Hun 2C

For part b of the problem it shows an already balanced redox reaction. I'm having trouble finding n for it because I don't know exactly how the charges for hydrogen and water would work.

Brittney Hun 2C

Hey Roomie! Since there is a flow of electrons, the salt bridge is used to balance the charges in the solution :)

Brittney Hun 2C

They are the same number, it's just another way to write is so the numbers seem smaller.

Brittney Hun 2C

I believe that if the reaction potential is positive then the reaction is spontaneous. They are related by deltaG = -nFE where E is the cell potential. If it is positive then delta G must be negative so it's spontaneous.

Brittney Hun 2C

For problem 6k.5 part a I don't see an oxidizing agent, since it doesn't look like the oxygen is being reduced. If oxygen is on its own are the redox numbers still 0 or are the values -2?

Brittney Hun 2C

Can something be both an oxidizing and reducing agent? If so, how is that possible and would we make two separate half reactions?

Brittney Hun 2C

It is not always the case, but they typically do not change. A special case is in a peroxide the charge on oxygen is -1 instead.

Brittney Hun 2C

Yes, since it has a charge of -1 that is the total charge you want to get at the end. Since oxygen has a -2 charge and there are 4 that makes it minus 8 so in order to get a net of -1 the remaining element would have a charge of +7.

Brittney Hun 2C

You would use the periodic table patterns and trends. Metals which are on the left of the periodic table will be a positively charged ion depending on the column (column 1 = +1 charge) and will go up to the fourth column. Non-metals, which are on the right of the periodic table, starting the fifth c...

Brittney Hun 2C

When do we know that the delta S of the universe is equal to 0. In the solutions manual it says that a reversible process has delta S=0

Brittney Hun 2C

in order to find q of the reaction, we must find q of the calorimeter, and since q of the reaction equals -q of the calorimeter, the final answer will be negative.

Brittney Hun 2C

I'm getting -138.13 so it might just be a calculation error!

Brittney Hun 2C

Use Table 4C.1 to find the enthalpy of fusion of water. Convert 80.0 grams of ice to moles and multiply by the enthalpy of fusion to get the heat needed to melt the ice. Then, use 80.0 g in the equation q= mCΔT to find the heat needed to raise the temperature from 0 to 25 degrees C. Do you know why...

Brittney Hun 2C

For expansion on a piston, the formula is work = -p*deltaV, but how do these units become joules?

Brittney Hun 2C

Bond formation is exothermic because when two molecules are joined together it is increasing stability, and the system is losing energy that gets released.

Brittney Hun 2C

I don't think you need to use the ideal gas equation. Heat capacity units are J/mol x K and they give you all of that information. The 1.00atm just shows that it is int he standard form.

Brittney Hun 2C

The problem is: how much heat is needed to convert 80.0 g of ice at 0.0 8C into liquid water at 20.0 8C? It says to use the table 4A.1 and 4A.C but I'm unsure of what information I need. The water is turning from solid to liquid, which is fusion. The enthalpy for the fusion of water is already given...

Brittney Hun 2C

How do you know the copper releases energy?

Brittney Hun 2C

Delta U stands for the change in internal energy of the system. Delta u = q (heat) + w(work). The units are in joules!

Brittney Hun 2C

Remember the property q(system) + q(surroundings) = 0, so this holds true for this problem as well but instead it's q(water) + q(copper) = 0. So we can deduce that q(water) = -q(copper). The copper decreased in temperature so the change in T will be negative, and that reveals that it is endothermic....

Brittney Hun 2C

I know for the k values when we added two equations together we would multiply the two k values, is it the same for the enthalpy values? What do we do when we need to reverse an equation or double it for enthalpy?

Brittney Hun 2C

qp(work at a constant temperature) does equal enthalpy. The units for a standard reaction enthalpy is kj/mol. q is typically just j or kj but i belive in order to get that you would just multiply by the number of moles in the system, but they are essentially the same value. Enthalpy, without being a...

Brittney Hun 2C

Where are you seeing the absence of mass in the equation. Correct me if I'm wrong but I think that it always includes mass, the only thing different is the negative sign in front that means that it is exothermic. It will either include mass or moles in the equation.

Brittney Hun 2C

Set up the equilibrium expression as k=[BrCl]^2/[Br2][Cl2] and set it to find [Br2] = 0.031*(.495/.145^2) to solve.

Brittney Hun 2C

pH shows the scale of acidity and how basic something is more so than the pKa. You can undo the pKA by raising it to 10^- and finding the Ka. By using an ice table you can find the pH using the equilibrium expression.

Brittney Hun 2C

Endothermic reactions require energy to proceed and temperature and adding heat acts as a reactant. This would have a positive delta H (enthalpy).

Brittney Hun 2C

You could also explain it by writing out the equilibrium expression where it shows k = [products] / [reactants]. This is simply a ratio, so if reactants increase it would only drive the entire reaction to the right, thus creating more products since k needs to remain constant.

Brittney Hun 2C

You would just have to memorize the six strong acids H2SO4 Sulfuric Acid, HCl Hydrochloric Acid, HBr Hydrobromic Acid, HI Hydroiodic Acid, HNO3 Nitric Acid, HClO4 Perchloric Acid. Everything else is considered a weak acid. Strong bases have a group 1 or 2 metal attached to a hydroxide (OH-). Everyth...

Brittney Hun 2C

A proton transfer is just the tranfer of a hydrogen ion (H+) in solution. You would write it as hydronium (H3O+) on the product side and the conjugate base along with it.

Brittney Hun 2C

If the Ka is large it means it's a stronger acid. The greater the number the more it dissociates so more H+ will be in solution.

Brittney Hun 2C

Another way to do it is to turn the pKa into Ka first. Once you turn it into ka you can use the kw (water constant) to find the kb. Set the equation to be kb=kw/ka.

Brittney Hun 2C

The reaction is reversed, so the k value would become 1/k. Putting the k value you got in part A over 1 should get you D as the answer.

Brittney Hun 2C

A closed system gas a fixed amount of matter, which in that sense makes it closed. Although it can still exchange energy with its surroundings through heat work and transfer. These energy forms can be transferred across system boundaries.

Brittney Hun 2C

I believe the trends are the same, just in the opposite direction. So the reaction will shift to the side that has less moles.

Brittney Hun 2C

Since it is 60% you would multiply the value by 0.60 and take that as the change.

Brittney Hun 2C

You make the two equations into composite equations. Use the two equations that has 2HCl as a product and Br2 + Cl2 as a product. Everything should cancel out and create the equation you are looking for. Make sure that when you add two chemical reactions together you multiply their k values. When I ...

Brittney Hun 2C

I believe you use the conservation of mass and you don't need an ICE table. Since k = [NH3]^2 * [CO2] you would use the equilibrium value of 17.4mg of CO2 to find the molarity of that (divide by 0.250L). Since the amount of solid ammonium carbonate initially is 25.0g you just subtract 0.0174g of the...

Brittney Hun 2C

I know that it doesn't matter what amount of reactants and products you begin with, and it still will have the same equilibrium concept, but I am still confused as to how that works? Does the reaction just continue until the ratio is reached?

Brittney Hun 2C

A polydentate ligand refers to ligands with more than one donor atom, meaning its elements can occupy more than one binding site simultaneously. They are typically ligands that have a central atom with a lone pair. To determine the number, it is just how bonds the polydentate can form.

Brittney Hun 2C

If there is both a strong acid and a strong base then they need to be subtracted from each other, to find out what there is more of, H+ or OH-. If there are equal amounts the pH would be neutral, but once they are subtracted it is the left over H+ or OH- that did not get bounded together, thus influ...

Brittney Hun 2C

Another way to determine how a salt will affect a solution is to write out the net ionic equation for the salt produced and separating the the cation and anion. If it produces a strong base, OH- will be produced (basic), and if the product is a strong acid, H+ will be produced (acidic).

Brittney Hun 2C

You should know that groups 1 and 2 form strong bases. For the strong bases, you should probably know the 6 common strong acids: HClO4, HCl, HBr, HI, HNO3, H2SO4.

Brittney Hun 2C

Make sure you know that zinc nitrate is Zn(NO2)2 because Zn has a 2+ charge. Then you attach and 2 OH- to Zn2+ in the reactants and attach and H+ to NO2-. A neutralization always forms water and the salt, so balance the chemical equation.

Brittney Hun 2C

Yes, they have unhybridized orbitals because resonance is the moving of pi orbitals, for various arrangements. The arrangement of pi bonds involves only unhyrbidized orbitals.

Brittney Hun 2C

The tetrahedral shape is never non-polar unless all elements surrounding the central atom are identical. It's easies to see the 3-D shape, and how they would not be able to cancel out.

Brittney Hun 2C

Does SO2 have a bent molecular shape, and if so is the VSEPR formula AX2E2.

Brittney Hun 2C

For problems such as J.7, in order to select an acid or base it seems we would just add an H+ to the conjugate base and an OH- to the conjugate acid but would the same apply to the zinc nitrite? Would the zinc be the conjugate base, but Zn(OH)2 doesn't seem like a base that we're familiar with.

Brittney Hun 2C

Dr. Lavelle posted a link on his site https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf
I was wondering if anyone knew if we needed to memorize the anionic ligands?

Brittney Hun 2C

How would we name this compound?

Brittney Hun 2C

The weaker the bond the stronger the acid. So the element that is the most electronegative (strong bond) will have a weak acid.

Brittney Hun 2C

Bronsted acids are defined as substances that can donate a hydrogen ion (H+) whereas Lewis acids are seen as simply electron-pair donors, and not specifically hydrogen ions.

Brittney Hun 2C

CHI3 has the higher boiling point because the molecule is larger. That overrides any of the IMF typically, and CHF3 does not have hydrogen bonding because the central atom is carbon so H and F are not bonded together.

Brittney Hun 2C

The lone pairs generally affect the polarity of a molecule because the long pairs distort the geometry of the molecule to be asymmetrical. When the molecule is not symmetrical it has polar properties. The arrows point toward H3 because the lone pairs repel the other atoms away.

Brittney Hun 2C

The bigger the molecule, the greater the IMF is a rule of thumb. The shape of the molecule is secondary to the amount of electrons, so we typically only compare that when they have the same number of electrons.

Brittney Hun 2C

I believe it's everything in the book, which includes part of the charts. I think we need to be familiar with the names and bond angles.

Brittney Hun 2C

A polar molecule must have polar bonds with dipoles that do not cancel each other out. So the electronegativity of atoms must be evident and typically on the same side of the central atom. Draw a lewis structure and then determine its molecular shape. It is determined the symmetry of the molecule (l...

Brittney Hun 2C

The rod shaped molecule is larger than the spherical shaped molecule, thus experiencing greater intermolecular london dispersion forces. Larger molecules=stronger attraction=harder to break bonds=higher boiling point.

Brittney Hun 2C

There can only be one sigma bond between two atoms because the orbitals form the two atoms overlapping it cannot bond again to share more electrons in another end to end overlap, therefore a pi bond is created instead (for orbitals to overlap side-to-side).

Brittney Hun 2C

Also remember that a triple bond has one sigma bond and two pi bonds!

Brittney Hun 2C

AsF3 has a higher boiling point than AsF5 because it has lone pairs that distort the geometry, therefore making the shape polar. But AsF5 is bigger, so does the dipole-dipole interaction have a greater influence in bond strength than the size of the molecule?

Brittney Hun 2C

I know the boiling point is higher for CHI3 than it is for CHF3 because CHI3 is the larger molecule so the dispersion forces are stronger and greater. But since Fluorine is more electronegative does that play any role in the strength of the forces, since it attracts the CH to it?

Brittney Hun 2C

Also, another question on this problem. How do we know that H2SeO4 has a dipole-dipole intermolecular force, and not an ion-dipole intermolecular force. Are ion dipole just for the ion being an element?

Brittney Hun 2C

Do we need to draw out the lewis structure every time we are determining what intermolecular forces are present for a molecule?

Brittney Hun 2C

The two exceptions from the general trend are the ionization energies of B is less than Be and O is less than N. They have greater electron shielding.

Brittney Hun 2C

The distance is the distance from one nucleus to another. It doesn't have a direct relation to electrons, but since the longer (weaker) the bond length, the easier it is broken, and it is more likely involved in a reaction (this is where the electrons come in).

Brittney Hun 2C

So I used two different equations to derive the energy because it's not asking for the energy of an electron, which is what the kinetic energy formula finds. I used E=hv, but found v first using v=c/lamda for part a.

Brittney Hun 2C

A coordinate covalent bond is when a shared pair of electrons comes from the same atom, and not a sharing between two different atoms. In a normal covalent bond each atom contributes one electron to make a pair. A coordinate covalent bond is held together because the electron pair is attracted by bo...

Brittney Hun 2C

Dipole moments are determined by the shape and structure of a molecule. So if there is charged asymmetry there is an electric field thus making it dipole. The equation u = q * d gives a mathematical representation. But if the molecule is asymmetric it has a dipole moment because the charges create t...

Brittney Hun 2C

Polarizability measures how easily an electron cloud distorted by an electron field (typically caused by cation and anion). If the electron cloud is easy to distort, it's polarizable.

Brittney Hun 2C

Polarizability measures how easily an electron cloud distorted by an electron field (typically caused by cation and anion). If the electron cloud is easy to distort, it's polarizable.

Brittney Hun 2C

I would stick to using dots as lone pairs since lines indicate single bonds and double bonds between two electrons, just to avoid confusion.

Brittney Hun 2C

The longer the bond length the lower the energy it takes to break that bond. The further away the element is from the nucleus of the central atom, then the easier it is to break.

Brittney Hun 2C

Since electron affinity is a neutral atom's likelihood of gaining an electron, what is the periodic trend? Does this have to do with filling its valence shell?

Brittney Hun 2C

Does the energy of an electron increase when it moves up an energy level/orbital?

Brittney Hun 2C

E=hv is also equal to the work function. What exactly is the work function and is it the threshold energy for the electron or for an element?

Brittney Hun 2C

How do we know that the Balmer series starts at n=2 and how the n= is found for the lyman series and what that ultimately means. Does this change how the other orbitals are calculated?

Brittney Hun 2C

I'm not entirely sure how to write the electron configurations using previous elements on the periodic table. How do we know when to use the previous elements.

Brittney Hun 2C

b)How many values of ml are allowed for an electron in the 6d subshell?

I am not sure how to start this. Should we find the l orbital first?

Brittney Hun 2C

Which observation shows that the electromagnetic radiation is particle like and not wavelike? -Black-body radiation -Electron diffraction -Atomic Spectra -The photoelectric effect I'm having trouble figuring out which one shows particle properties because everything seems to describe wave properties...

Brittney Hun 2C

You need to use the definition of the quantum numbers to describe the location and spin of an atom. The d sub shell in c (described by l=2) can only hold a total of 5 orbitals, so c is not a valid set of numbers since the absolute value of the magnetic quantum number cannot exceed the value of the a...

Brittney Hun 2C

Is there a specific problem, or just a general question? Typically electrons are assigned quantum numbers when the orbitals are needed for the equations or you want to know the size of the orbital that the electron resides in. This creates different properties and energy required needed to remove th...

Brittney Hun 2C

De Broglie's equation is used to determine if matter has wavelength properties, but it is only noticed for moving objects with momentum (p) and objects with extremely small mass. The wavelength can be measured using this equation, where mass determines the outcome. Make sure that these calculations ...

Brittney Hun 2C

There are multiple ways to finding the limiting reagent. You could also start with the grams of water and see how much water is needed in moles or grams to complete the reaction (since it is the product) and then find how much o2 we already have. You can compare those values and see how much is exce...

Brittney Hun 2C

For part b of the problem that states: Estimate how many moles of each product will be produced and how many moles of the excess reactant will remain, how do we find the amount that remains. I understand the excess reactant is the BrF3 and found that 2 moles of Br2 is produced, but where do I go fro...

Brittney Hun 2C

For question H.11 it states: "In a second stage, the Fe3O4 reacts further with carbon monoxide to produce solid elemental iron and carbon dioxide. Write the balanced equation for each stage in the process." For the first part I balanced the equation and got 2 moles of Fe3O4. Does this numb...

Brittney Hun 2C

It doesn't really matter that boron is diatomic because you are just finding the grams of all the boron in the compound! It is essentially already taking into consideration that boron is diatomic, so it doesn't affect your calculations. The moles of the element stays the same regardless of how "...

Search found 104 matches