CHEMISTRY COMMUNITY

Becky Belisle 1A

Phone batteries are more complex than the examples we've been using. While a lithium-ion battery is charging, it can be considered an electrolytic cell.

Becky Belisle 1A

Writing the anode half reaction and cathode half reaction is one way to determine the number of electrons transferred. You can also just look at the charge difference between the two substances in a redox pair. In 6L.1b, a redox pair is Fe3+ and Fe2+. Since there are 6 of Fe3+ that means the charge ...

Becky Belisle 1A

They are both hydrogen, which is always 0V because it is used set all the other values for other substances.

Becky Belisle 1A

I've noticed other errors concerning the value of n in the solution manual as well.

Becky Belisle 1A

Based on the assigned textbook exercises, we only need to know how to do calculations with zeroth, first, and second-order reactions.

Becky Belisle 1A

I don't think there are any exceptions for the types of reactions we will be working with in 14B.

Becky Belisle 1A

I assumed that was a solution manual error.

Becky Belisle 1A

Concentration does impact cell potential, as demonstrated by the Nernst equation.

Becky Belisle 1A

You add an inert electrode, such as Platinum, when the anode or cathode is lacking a metal in the solid state. For instance, when the substances in the cathode are both aqueous, Platinum could be added.

Becky Belisle 1A

The easiest way to know is by using the octet rule to figure out how many electrons the element usually gains or loses.

Becky Belisle 1A

I think Gibbs free energy is extensive because energy does depend on the amount.

Becky Belisle 1A

I think KJ is best, but it should not really matter.

Becky Belisle 1A

For 3b: the first step is to calculate the amount of heat need to raise the temperature of all the ice cream to 0 degrees C. Then, you subtract this value from the total heat that was given. Next, you set the value for heat from the subtraction equal to the half the mass of the ice cream multiplied ...

Becky Belisle 1A

The formula for internal energy is: ΔU= q + w, so when volume is constant, w=0. Thus, when no work is done, ΔU = q. ΔH = q at constant pressure because if the pressure changed that would affect the enthalpy, but not the heat transfer.

Becky Belisle 1A

ΔU = 0 when a process is isothermal.

Becky Belisle 1A

w= -PΔV should be used for irreversible expansions, and it is probably stated in the question if the process is irreversible. w=-nRTln(V2/V1) is for reversible expansions.

Becky Belisle 1A

Heat capacities change based on the amount of particles. Specific and molar heat capacities are for specified quantities of particles, so they are intensive.

Becky Belisle 1A

Since the pKa of benzoic acid is given, the first step is to find the pKb of its conjugate base (C7H5O2-). This can be found using pKa+pKb=14. Next, the Kb can be found by raising 10 to the power of -pKb. Then use an ice table, set up the Kb equation, and set the equation equal to the value found fo...

Becky Belisle 1A

At 0K, if the structure is perfectly ordered, then entropy is equal to zero. However, if there are still possible microstates, the entropy will not be equal to zero.

Becky Belisle 1A

Cv can be used when the entropy change is being addressed by multiple steps. For example, the entropy change can be calculated for the change in volume with ΔS=nRln(V2/V1). Then, the entropy change can be calculated for the change in temperature with ΔS=nCln(T2/T1). Since entropy is a state function...

Becky Belisle 1A

When I use the equation you provided, I get 64,482.8 J, which equals the answer provided in the review session.

Becky Belisle 1A

Solutions of strong acids have a higher pH than solutions of weak acids of the same the molarity. For weak acids: the weaker the acid, the greater the pKa.

Becky Belisle 1A

If an expansion is isothermal, the change in temperature equals zero. If an expansion is reversible, w= -nRTln(V2/V1). For irreversible expansions, pressure is treated as constant. So, w= -PexΔV.

Becky Belisle 1A

The heat being added is energy, and that energy goes toward changing the phase, breaking bonds, not towards heating the substance.

Becky Belisle 1A

C can be substituted with Cv=(3/2)R or Cp=(5/2)R if the substance in question is an ideal gas.

Becky Belisle 1A

The problem provides the change in enthalpy at 200°C, so the first step is to heat up the reactants from 37°C to 200°C. This is why the change in temperature equals 163°C. I do not see any values of 11.3 or 16.3.

Becky Belisle 1A

The mass of ice is in grams, specific heat capacity is in J/(°C x g), and temperature is in °C. Thus, when mCΔT is multiplied out, the units should all cancel besides Joules.

Becky Belisle 1A

The reaction is being considered when 1.00 mol CO2 has formed. Thus, 0.5 mol PG and 0.25 mol BG reacted to form 1.00 mol CO2 and 0.25 mol H2O. The initial amount of moles was 0.75 and the final amount of moles was 1.25. Thus, delta n is 0.5 mol.

Becky Belisle 1A

Standard enthalpies of formation are often given so that you can solve for the standard reaction enthalpy. ΔH(rxn) =ΣΔHf(products) - ΣΔHf(reactants)

Becky Belisle 1A

3/2R is the C value at a constant volume. It can be used in the equation ΔS=nCln(T1/T2). In this equation, C can be substituted with Cp (constant pressure) or Cv (constant volume) depending on the problem.

Becky Belisle 1A

Do you mean residual entropy? If so, residual entropy can be best understood in comparison to residual entropy of a crystalline structure nearing 0K. The residual entropy is zero in this situation because the degeneracy (number of possible microstates^number of molecules) is equal to 1, and S=kBln(W).

Becky Belisle 1A

For part b, internal energy is a state function, so although 2 different path are given, Δ U is still equal to zero. State functions are path independent.

Becky Belisle 1A

Isothermal means the change in internal energy equals zero, and since Δ U = q + w, q = -w.

Becky Belisle 1A

W is degeneracy and kB is the boltzmannn constat.

Becky Belisle 1A

I think the degeneracy of one mole equals 2 raised to avogadro's number because N equals the number of atoms/molecules.

Becky Belisle 1A

I think we usually are assuming ideal gas in this unit.

Becky Belisle 1A

I just checked the solutions manual again to make sure. The mercury is a closed system, and the manual says that.

Becky Belisle 1A

It should always take energy when breaking bonds and release energy when forming bonds. However, the standard enthalpy of formation for an element is zero when it is in its standard state. For example the bond enthalpy of O2 (Oxygen) is zero.

Becky Belisle 1A

I do not think there are any that are excluded.

Becky Belisle 1A

It depends on which defintion you use. A Bronsted acid donates a proton, so it must at least have a proton in the formula.

Becky Belisle 1A

If you are given the Ka and it is very very small then sometimes it can be assumed that less than 5% of the acid was deprotonated. I think it also has to do with memorizing which acids and bases are very weak.

Becky Belisle 1A

I think the noble gases are inert since they have 8 valence electrons.

Becky Belisle 1A

Using quizlet to remember important things is also very helpful.

Becky Belisle 1A

I think it would be based on the equilibrium constant. If products are favored, they are more stable. If reactants are favored, they are more stable.

Becky Belisle 1A

Kw = [H3O+][OH-]

Becky Belisle 1A

If you are confused about a specific topic the search tool on here is very helpful. Sometimes I'll google a question I have and the top result is this website.

Becky Belisle 1A

The reaction quotient still has the same formula as the equilibirum constant, except for the equilibrium constant the values used are the ones at equilibrium.

Becky Belisle 1A

I think you would first convert the partial pressures to concentrations.

Becky Belisle 1A

I don't think you can know without more information, such as the charge of the transition metal.

Becky Belisle 1A

The other reactant is oxygen. So the mass of the oxygen contributes to the mass of the products.

Becky Belisle 1A

I think there are some ways to tell. For example, H2PO4-, it is apparent it can accept a proton because it has a negative charge, but it also has protons to donate.

Becky Belisle 1A

I think it's useful to memorize the oxidation states of the common ligands.

Becky Belisle 1A

what do you mean extra p orbital? sp is 2 regions of e- density, sp2 is 3 regions, sp3 is 4 regions, sp3d is 5, sp3d2 is 6.

Becky Belisle 1A

I think just knowing that iron is ferrate is enough.

Becky Belisle 1A

I think the arrow should always point toward the negative.

Becky Belisle 1A

They have to have unpaired electrons not lone pairs.

Becky Belisle 1A

Yes, it tells you how many bonds an atom can form. Which explains why atoms like carbon form hybridized orbitals.

Becky Belisle 1A

It seems that in the VSEPR model the chlorine atoms are next to each other and the oxygens are next to each other.

Becky Belisle 1A

Based on the way we took notes in class, that would make sense.

Becky Belisle 1A

Singe, double, and triple bonds have the same effect for determining the shape of a molecule. The shape is not different depending on the order of the bond.

Becky Belisle 1A

I think slightly less than has to do with lone pairs affecting what the angle normally is for a certain structure.

Becky Belisle 1A

Probably the questions from 2E.

Becky Belisle 1A

Covalent or Ionic bonds

Becky Belisle 1A

And more electrons mean the radius of the atom is larger.

Becky Belisle 1A

I think more electrons increases the probability of electron distortions.

Becky Belisle 1A

Stronger forces mean the atoms/molecules are closer together and less mobile. Thus, they are solid.

Becky Belisle 1A

I think oxygen forms two bonds typically and fluroine forms one. This is based on how many electrons they need for the octet guideline.

Becky Belisle 1A

It is easier to remove the outermost electrons, which are the ones in 4s.

Becky Belisle 1A

I think it's based on the energies of those sublevels. 4d has lower energy than 5s, and the electron configurations are written in order of increasing energy.

Becky Belisle 1A

The equation should always be final minus initial. So E= -hR (1/n_final² + 1/n_initial²)

Becky Belisle 1A

λ=hc/E is the same as λ=h/p except because c is used it is specific to light. λ=h/p cannot be used for light because p=mv and photons are massless.

Becky Belisle 1A

The first ionization energy is the energy required to remove an electron from a neutral atom (same number of protons and electrons), whereas the second ionization energy is the energy required to remove an electron from an ion with a charge of 1+. The atom is an ion because the number of electrons i...

Becky Belisle 1A

This is Schrodinger's Equation:

A simpler form is:
Hѱ= Eѱ

Becky Belisle 1A

Becky Belisle 1A

I think the seven problems can come from any of the sections. For example, in my homework this week I chose to do only problems from 1D. It does not matter that we have not covered everything from this section in lecture yet.

Becky Belisle 1A

Theoretical yield is larger than actual yield because the actual yield comes from experiments. In experiments, competing reactions may occur, the reactants may not react fully, and the reaction may not have gone to completion. Other explanations for why the maximum product was not produced are also ...

Becky Belisle 1A

In 0.0490, the significant zero is only the one in the ten-thousandths place. I remember this rule because this zero shows more precision in the measuring equipment used. If the number was 0.0409, the zero between the 4 and 9 would be a significant figure.

Becky Belisle 1A

I think when it says "quantized or discrete" that discrete is just serving as a definition or qualifier for the word quantized. The difference between them is not the main point. When values are quantized they become discrete.

Becky Belisle 1A

I think it's best to use sig figs in all problems. When doing addition or subtraction, the number with the least digits after the decimal determines how many digits can be after the decimal. For Example: 1.82 + 2.1 = 3.9.

Becky Belisle 1A

I was also confused at first by this problem. The first step is to calculate the molar mass of (OH) 2 using a periodic table. Then, this value can be subtracted from the given molar mass of the metal hydroxide. This will give you the molar mass of the unknown metal. Using a periodic table you can fi...

Becky Belisle 1A

Prefix : Name: Meaning: G giga 10^9 M mega 10^6 k kilo 10^3 d deci 10^(-1) c centi 10^(-2) m mili 10^(-3) μ micro 10^(-6) n nano 10^(-9) p pico 10^(-12) Volume: m^3 (extensive property: dependent on size) Density: kgm^(-3) (intensive property: independent of size) Bond lengths are 1 x 10^(-10) m, w...

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