CHEMISTRY COMMUNITY

madawy

Ecell should be E(cathode/reduced) - E(anode/oxidation). If the negatives worked out that way, there should be scenarios in which you could add the potentials of the half reactions to find the total potential

madawy

Adding mass of reactants/products at the anode or cathode will not affect the cell potential, as Eº (and E) are intensive properties and do not depend on the quantity of oxidizing or reducing agents present.

madawy

https://chem.libretexts.org/Courses/Heartland_Community_College/HCC%3A_Chem_162/20%3A_Electrochemistry/20.6%3A_The_Nernst_Equation this site explains it really well! It has to do with the Nernst Equation and since these galvanic cells deal with concentrations of various sorts, we see the relationshi...

madawy

In a galvanic cell, the Gibbs free energy is related to the potential by: ΔG°cell = −nFE°cell. If E°cell > 0, then the process is spontaneous (galvanic cell). The Gibbs free energy is thus the maximum amount of non-expansion work that can be extracted from a closed system.

madawy

Free energy of activation refers to Gibbs free energy. This is what we usually refer to when we are looking at the energy barriers of chemical reactions. Activation energy can be referred to the energy that is needed to get over the energy barrier of each transition step. The Energy of activation is...

madawy

A typical pH meter has two basic components: the meter itself and either one or two probes that you insert into the solution you're testing. A pH meter kind of works like a voltmeter: it measures the voltage (electrical potential) produced by the solution whose acidity we're interested in, compares ...

madawy

What is the difference between a galvanic and an electrolytic cell? thanks!

madawy

I was confused about this as well, so here's where I found the solution! "This problem is a little tricky. First, the solutions uses the equation O3O2 so that is not incorrect. You are also correct in that the oxidation number of ozone and oxygen gas are not changing, however, they do donate el...

madawy

You would go about this question using the stoichiometric coefficients of the balanced equation. Since there is one mole N2 and three moles of H2, H2 is going to be formed three times faster than N2 is going to be consumed, so the rate of consumption for N2 is 1/3. Hope that helps w the next time!

madawy

Basically the unique rate for aA + bB --> cC + dD is -1/a(d[A]/d[t]) + -1/b(d[B]/d[t]) --> 1/c(d[C]/d[t]) + 1/d(d[D]/d[t]). You are given the unique rate 0.44 mol/Ls. In order to find (a), you set 0.44 = 1/3(d[A]/d[t]), so to solve for (d[A]/d[t]), 0.44 * 3 = 1.3 mol O2/Ls. You do the same for water...

madawy

handy steps found online :) To determine if a redox reaction has occurred and to identify the element oxidized and the element reduced: Assign oxidation numbers to all atoms in the equation. (NOTE: Ignore the coefficients in the equation. They are not important when determining the oxidation numbers...

madawy

I'm assuming you mean in an equation where the charges are implied but not explicitly stated? In which case you would assign charges to the individual atoms until it adds up to the charge of the entire molecule. You'll see which atoms gain electrons and which lose electrons from one side of the equa...

madawy

Eo is measured under standard conditions and it is a measure of the electron-pulling power of a single electrode.

madawy

An isochoric process, also called a constant-volume process, an isovolumetric process, or an isometric process, is a thermodynamic process during which the volume of the closed system undergoing such a process remains constant.

madawy

I'll start with a basic definition: Potential difference is the amount of work energy required to move an electric charge from one point to another (measured in volts).

madawy

e start off with Cl2 + S2O3 2- --> Cl- + SO4 2- 1) Write half reactions. Use the Cl's to make a half reaction and the S2O3 to make the other 2) Balance the reaction but disregard O and H (we'll balance those later) So balance the Cl and the S and we get S2O3 2- --> 2SO4 2- (we'll call this the 1st H...

madawy

Hey! I found this to get you started :)

http://sites.duke.edu/apep/files/2016/0 ... ure-09.gif

madawy

you could say that heat is basically a “reactant” when the process is endothermic! If the system doesn’t receive enough heat, it cannot form it’s theoretical yield even if the chemical reactants are in excess.

madawy

The difference between the two is that delta G naught is at standard conditions. The reason Professor Lavelle emphasized it is because delta G naught is always the same because it is referring to when the reactants/products are at standard temperature/pressure. As the rxn goes towards equilibrium, d...

madawy

i believe it’s okay just to understand the equation's relationships and applications with delta H and delta S !! Usually aren’t tested on derivatives in this class

madawy

The standard Gibbs Free Energy is calculated using the free energy of formation of each component of a reaction at standard pressure. The Gibbs free energy equation is dependent on pressure. When a system changes from an initial state to a final state, the Gibbs free energy (ΔG) equals the work exch...

madawy

personally, I would just base it off the parameters of the problem and what they give you. I found this online, though: More specifically, q=mcat is for a SUBSTANCE. So if youre trying to find how the amount of temperature it takes to heat water 1°C, the only substance is water. Use this for coffee ...

madawy

should be something like this:
heat released = heat absorbed
20 (mass)*0.39 (specific heat of Cu) *(100-T) (change in temperature) = 50.7 (mass)* (specific heat of H2O) *(T-22)(change in temperature)
20*0.39*(100-T) = 50.7*4.18*(T-22)
= about 25

madawy

According to the textbook, the cis compound has 12 different orientations while the trans compound only has three different orientations, decreasing the entropy due to the fact that there is less uncertainty in its orientations. In regards to entropy, residual entropy is the measure of how many diff...

madawy

The first law of thermodynamics, also known as Law of Conservation of Energy, states that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another. Just because the universe is technically an isolated system, doesn't mean that the systems within...

madawy

I believe the negative sign would be given to the water, since the water is giving off its eat to melt the ice cube, which is absorbing the heat in order to change phases.

madawy

In a reversible process, at each point along the process path, the system is only slightly removed from being in thermodynamic equilibrium with its surroundings. So the path can be considered as a continuous sequence of thermodynamic equilibrium states. For an irreversible process, the system is not...

madawy

Start out by balancing the equation: 2HCl + Zn --> H2 + ZnCl2 Find the limiting reactant (Zinc). Now use Hess's law to find the Heat of the reaction (ΔHrxn), which is just the sum of the heats of formation of products minus the sum of the heats of formation of the reactants. This should give you the...

madawy

There are multiple "check lists" that have to be met for a bond to form between to entities: these are called the steric effects. For example, orientation of the two molecules and the speed at which they collide are two crucial components.

madawy

When there's a reaction at constant pressure that involves solids and liquids, a change in volume will be insignificant because V of the reactants will equal (or almost equal) V of the products. ΔV=0, so PΔV=0. Also, there is no expansion work. Thus, with constant pressure, for a reaction that invol...

madawy

W=-P external x the change in volume! We can observe the increase in average kinetic energy of the molecules by measuring how the temperature of the gas increases. As the gas molecules move faster, they also collide with the piston more often. These increasingly frequent collisions transfer energy t...

madawy

I believe that’s heat capacity based on the units (:

madawy

You are given delta H (since it tells you 5.50 kJ of energy is gained assuming the pressure is constantly 750), as well as the change in volume (deltaV when you subtract initial volume from final) and the current pressure (P). To find the change in internal energy (delta U), I would use this equatio...

madawy

yes! Do go down a phase means to lose energy (ie how gas particles have much more energy than a solid). that energy is thus released in the form of heat.

madawy

state functions basically just mean that the path is irrelevant and it can be determined by calculating the difference between final and initial values. intensive and extensive properties, however, are properties that are particular to the quantity of matter.

madawy

I suppose it’ll be based off of the information given and parameters of the question/experiment !!

madawy

Which known gas behaves the most ideally? Why? Is it possible to achieve ideal gas behavior under extreme conditions such as incredible temperatures and pressures?

madawy

What is the approximate error of using ideal gases to calculate real world problems? Is it always appropriate, or are measurements preferred to be calculated through experiments?

madawy

This is what I have in my notes in regards to the salts that an acid/base reaction produces: - If salt has neutral ions, then solution is neutral: HCL (aq) + NaOH (aq) ----> NaCl (aq) + H2O (l) - Where the salt does not affect the pH… thus it is neutral. - If salt has acidic ions, the solution is ac...

madawy

There is no hydronium in the equation due to the fact that water is acting as an acid. Instead of gaining a proton to become H3O+, it transfers one to NH3 to become OH-.

madawy

Percent ionization is defined as the amount of a weak acid that exists as ions at a particular concentration, meaning that it is the amount of the acid that has dissociated. The part that is "left" as a weak acid in the solution would be the remainder.

madawy

I always dedicate most of my time to what HE spends the most time on in lecture! Also, be sure to note every connection he makes to the real world and the human body etc because it’s often featured on tests. Otherwise just go over all the hw problems and focus on what you don’t understand 100%!

madawy

Can someone repeat the reason pressure doesn't actually affect the equilibrium constant? I know it has something to do with the concentrations, but my notes don't make a lot of sense. Thanks!

madawy

Once you determine the K of both dissociations by using the ICE table, you figure out that the K of chlorine is smaller than the K of fluorine. As a result, you know that in dissociation equilibrium, chlorine favors its reactants more (since K = concentration of products/concentration of reactants) ...

madawy

Pure solids or liquids are excluded from the equilibrium expression because their effective concentrations stay constant throughout the reaction. The concentration of a pure liquid or solid equals its density divided by its molar mass. The density of a pure liquid or solid is the same, regardless of...

madawy

will someone please explain why the following statement is true? thanks!
"If one starts with higher concentrations of reactants, the equilibrium concentrations of the products will be larger."

madawy

Whenever you see a "p" in front of a value, like pH, pKa, and pKb, it means you're dealing with a -log of the value following the "p". For example, pKa is the -log of Ka. Because of the way the log function works, a smaller pKa means a larger Ka.

madawy

How do you find relative acidity???

madawy

yeah, we turn in two to make up for last week.

madawy

For any molecule draw the Lewis structure. There is one pi bond for every double bond and two pi bonds for every triple bond. There is one sigma bond for every single bond, double bond, and triple bond... thus, H2S has two sigma bonds and no pi bonds. SO2 has two pi bonds so that is 2 sigma and 2 pi.

madawy

Yep. By definition, a Lewis base is is any species that donates a pair of electrons to a Lewis acid.

madawy

I would say no because carbon is not past the 3p orbital and thus doesn't have that extra space that the d-block elements have.

madawy

The transition metals form coordination compounds more than any other due to their availability of vacant d orbitals-. Transition elements have the electronic configuration ns2(n-1)d 0–10 and hence have empty d orbitals to accommodate or accept electrons coming from the ligands that are attached to ...

madawy

I believe he curves our total grade after all the points have been added up.

madawy

I would attribute the polarity of a molecule to the electronegativity differences in the atoms. Carbon dioxide, for example, contains two pi bonds and is non polar due to its linear shape/symmetry while carbon monoxide is polar (oxygen is more electronegative than carbon).

madawy

The Bronsted-Lowry theory talks about removal or transfer of hydrogen ions (H+) ie. protons where as the Lewis theory talks about donation or acceptance of electron pairs. A Brønsted–Lowry acid is a chemical species being able to donate a hydrogen cation, H+. Obviously, it needs another chemical spe...

madawy

Yep! I believe so.

madawy

According to the interweb, the Octet Rule is violated in these three scenarios: When there are an odd number of valence electrons When there are too few valence electrons When there are too many valence electrons Xenon is able to have an expanded octet, which can occur when the central atom with an ...

madawy

First, calculate the amount of electrons that the molecule should have: N= 2 * (5) + O= 6 =16 Thus, when you write N N O, giving each a single bond such that it is N--N--O and filling in the lone pairs so that each has a full valence, you get a total of 20 electrons. Thus, you need to add two more b...

madawy

Lone pair repulsion: Bond angle is affected by the presence of lone pair of electrons at the central atom. A lone pair of electrons at the central atom always tries to repel the shared pair (bonded pair) of electrons. Due to this, the bonds are displaced slightly inside resulting in a decrease of bo...

madawy

Which bond angles correspond to which shapes? And do you just have to remember the exceptions of those that are 106, 107, etc or is there a way to tell?

madawy

exactly! we should be able to figure out the shape from the lewis structure & formula and then predict the geometric shape from there.

madawy

When determining the central atom of a lewis structure, is formal charge more important than which atom is most electronegative ??

madawy

It increases across down a group because the elements have valence electrons in the same orbital, but the ones further down have more electrons in the same orbital, thus increasing its attraction to the nucleus. For this reason, it’s really hard to remove an electron. Increasing across a period, the...

madawy

We won’t have to calculate anything with schrodingers- just know the concept behind it! We just need to know that wave functions are the mathematical represent of orbitals and how we study them, but there shouldn’t be any questions/calculations on that either.

madawy

honestly i find it easiest to try and understand the reasons behind them !! Most of it corresponds to the amount of orbitals/amount of electrons in a single orbital. E.g. the more electrons in a single orbital means the stronger of an attraction it’ll feel to the nucleus etc etc which correlates to ...

madawy

The effective nuclear charge is the net charge an electron experiences in an atom with multiple electrons. Depending on the spins and the placement of electrons, the effective nuclear charge is often less than the actual nuclear charge.

madawy

It is a lot easier for metals to lose electrons when they bond with nonmetals. For example, Mg can have a full valence shell of eight if it loses its 2 electrons in its outermost shell. This is a great contrast to Chlorine, for example, which has seven electrons in its valence. It is so much easier ...

madawy

It all has to do with the D- orbital of said electrons! Elements of the third row in the periodic table and beyond can carry more than 8 electrons on their outermost shell because of the additional room (space) on their orbital d. Only elements of the first and second rows of the periodic table can ...

madawy

I remember Lavelle telling us that the amount of resonance structures correlates to come feature of the atom, but I forgot to write it down? Does anyone remember?

madawy

Definitely up to Chemical Bonds but I feel like we might get through some, if not most, Molecular Shape and Structure, too!

madawy

Ground state refers to the lowest energy state regardless of whether it is an atom OR an ion.
For example, the ground state of the sodium cation is Na+

madawy

1D.3 Evaluate the probability of finding an electron in a small
region of a hydrogen 1s-orbital at a distance 0.55a0 from the nucleus
relative to finding it in the same small region located at the nucleus.

Does anyone know how to do this problem? Thanks.

madawy

The fact that the emission is ultraviolet tells you that this transition is in the Lyman series, so n2=1 -Convert 102.6 nm into the energy E using the two relations: E=hv and \lambda \nu = c -Then plug into the rydberg formula and solve for n1 Balmer series is the visible region of the light spectru...

madawy

The s subshell has 1 orbital that can hold up to 2 electrons, the p subshell has 3 orbitals that can hold up to 6 electrons, the d subshell has 5 orbitals that hold up to 10 electrons, and the f subshell has 7 orbitals with 14 electrons. As to the explanation of the Aufbau rule and the order in whic...

madawy

Will someone please explain to me how Aluminum has a higher ionization energy than Sodium? Thanks.

madawy

Does anyone know why they based the mole off of Carbons AMU? Why wouldn’t they rather use a standard whole number?

madawy

Unfortunately, you’d have to compare whether or not the amount of moles you have is greater than the amount of moles you need; sometimes you can get a hint from the ratios, but most of the time the stoichometric coefficients and the sheer amount are not enough to tell

madawy

Definitely use the sigfigs of the values given in the problem since they represent the experimental data. We, personally, did not measure the AMUs, for example, so we don’t have to abide by the amount of digits

madawy

That is correct! The equation is still equal since the Molarity also changes proportionally... so even though V1 is 10mL and V2 is 30mL, the molarity ed shift so that M1V1=M2V2 still.

madawy

Is there any benefit (other than a better comprehension of the material) to turning in more than 5 hw problems or, in this week’s case, turning in problems from both the Quantum and Fundamental units?

Search found 81 matches