CHEMISTRY COMMUNITY

Jessica Chen 1F

SO2Cl2(g) → SO2(g) + Cl2(g) is an example of a first order reaction

Jessica Chen 1F

An example of a 2nd order reaction is
O + O3 → O2+ O2

Jessica Chen 1F

Technically, yes, because when you find the order of A and B by dividing the rate laws, the exponent (z) of [C] would be 0 because it is a zero-order reaction, which would make the value of [C]^z = 1 and thus irrelevant to finding the orders of A and B.

Jessica Chen 1F

You can tell that molecule C is a zero order reaction because when you divide the equations (you select the 2 equations where the concentration of A and B are the same and only C is different, which would be in experiment 1 and 4), you get 2/2 = (7/4)^z Since 2/2 is 1, Z has to be 0 in order for (7/...

Jessica Chen 1F

It doesn't matter what order you go in, you just have to make sure the ratio of the rates is in the same 'order' as the ratio of the concentrations. For example, rate 1/rate 2 = k [A]1 / k[A]2.

Jessica Chen 1F

For 7A.17, they just happened to choose the first experiment and plugged in the values to get the rate constant k. All the experiments should get you approximately the same k value.

Jessica Chen 1F

IsabelLight2H wrote:Are there units for K?

For a zero-order reaction, the units for k will be units of concentration/time (M/s).

Jessica Chen 1F

E naught is under standard conditions so it is a constant for a reaction, while E can vary under different conditions.

Jessica Chen 1F

The reaction order is the relationship between the concentrations of species and the rate of a reaction, so a zero-order reaction would be one where the rate is independent of the concentration of the reactants, while a first-order reaction is one where the rate of reaction is directly proportional ...

Jessica Chen 1F

Gibbs free energy (G) is the measure of the total amount of energy available to do work while entropy (S) is the measure of the disorder of the system. Gibbs free energy is calculated using enthalpy (H), temperature (T), and entropy (S) with the equation delta G = delta H - T(delta S).

Jessica Chen 1F

Since the equation to calculate for delta G is delta G = delta H - T(delta S), a small/negative delta H (enthalpy), large/positive T (temperature), and a large/positive S (entropy) would make for a very small/negative delta G.
The opposites would make delta G larger (more nonspontaneous).

Jessica Chen 1F

Since delta G is calculated for by the equation delta G = delta H - T(delta S), the factors that affect delta G are the enthalpy of reaction, the temperature that the reaction takes place at, and the entropy. A negative enthalpy, high temperature, and high entropy makes for a spontaneous reaction (n...

Jessica Chen 1F

A reversible reaction would also have more work done and is isothermal (temperature remains constant.)
An irreversible reaction would have less work done and is isobaric (pressure remains constant).

Jessica Chen 1F

The heat of vaporization is a lot larger than the heat of fusion (40 kJ vs 334 J) so when steam condenses back into water, it releases all 40 kJ into the skin, which creates more severe burns.

Jessica Chen 1F

If the reaction is exothermic, heat is a product and increasing the temperature would cause the reaction to shift toward the reactant side, making reactants more stable and products less stable. If the reaction is endothermic, heat is a reactant and increasing the temperature would cause the reactio...

Jessica Chen 1F

In part (a), the equation you use to calculate the standard enthalpy of vaporization is delta S (vap) = delta H (vap) / T(boiling point in K). So you get delta H (vap) = (85 J/K)(80 + 273 K) = 30,005 J or 30.0 kJ. For part (b), the standard entropy change of the system is calculated by multiplying t...

Jessica Chen 1F

The degree symbol means that the reaction is happening in the standard state, which is at 1atm and 298.15K (or 25°C).

Jessica Chen 1F

U is a state property/function because it does not depend on the path taken to get to its present state and also describes the equilibrium state of the system. That is why you can add or subtract separate internal energies to calculate the total internal energy.

Jessica Chen 1F

delta U is 0 for it to be isothermal, but that doesn't mean work also has to be 0. Since delta U = q + w, that just means that q + w has to equal 0. Work has to cancel out the heat.

Jessica Chen 1F

Bond enthalpies are the least accurate way of measuring reaction enthalpies because they are made of multiple averages and thus an overall average.

Jessica Chen 1F

R is 0.08206 in the PV=nRT formula because its units are L atm K-1 mol-1 in that case.
R is 8.314 in the w=-nRTlnV1/V2 formula because its units are J K-1 mol-1 in that case.

Jessica Chen 1F

An example of the conjugate seesaw could be NaOH.
NaOH is a strong base, but its conjugate acid, Na+, is so weak that it's basically a neutral cation and won't affect the pH of the solution.

Jessica Chen 1F

Acids generally have an H+ in their chemical formula (e.g. HCl, HNO3, HClO4, NH4+ etc.)
Bases usually have an OH- in their chemical formula (e.g. NaOH, KOH etc.)

Jessica Chen 1F

The anions of strong acids, which include Cl-, Br-, I-, NO3-, ClO4-, are such weak bases that they have no significant effect on the pH of a solution so they are basically neutral. The cations of Group ½ elements (also those with charge +1 from other groups) are such weak acids that the hydrated ion...

Jessica Chen 1F

Solids and liquids are excluded from K calculations because their concentrations/densities remain constant (1) throughout the reaction. On the other hand, the concentrations/densities of gases and aqueous solutions are changeable and thus we need the ICE chart to solve for concentrations at equilibr...

Jessica Chen 1F

We can deduce that Cl2 is more thermodynamically stable than F2 because there is more Cl2 at equilibrium than F2 with the same pre-conditions.

Jessica Chen 1F

Temperature changes the equilibrium constant because temperature permanently affects the rate constants of the forward and backward reactions, which thus, in turn, affects Kc. On the other hand, if pressure or concentration of reactants/products are changed, the reaction will shift towards equilibri...

Jessica Chen 1F

I think he meant to differentiate between "sitting" and "shifting". When equilibrium 'sits' to the right, reactants are favored, and when it 'sits' on the left, products are favored. On the other hand, "shifting" means that the reaction is moving towards equilibrium (wh...

Jessica Chen 1F

The equation definitely has to be balanced before you plug things in to solve K because the stoichiometric coefficients matter as the exponents.

Jessica Chen 1F

You can use the equation Q = [(pC)^c(pD)^d] / [(pA)^a(pB)^b] and plug in the partial pressures into A, B, C, D and the stoichiometric coefficients into a, b, c, d.

Jessica Chen 1F

The 8 strong bases would probably be good to know:

1. LiOH
2. NaOH
3. KOH
4. RbOH
5. CsOH
6. Ca(OH)2
7. Sr(OH)2
8. Ba(OH)2

Jessica Chen 1F

The definition of a strong acid is that they completely dissociate in solutions and thus, they give off more protons. Weak acids may not completely dissociate and/or dissociate less than strong acids so they won't give off as many protons.

Jessica Chen 1F

We should probably also know the general 8 strong bases and 7 strong acids:
Bases
1. LiOH
2. NaOH
3. KOH
4. RbOH
5. CsOH
6. Ca(OH)2
7. Sr(OH)2
8. Ba(OH)2

Acids
1. HI
2. HBr
3. HCl
4. HClO3
5. HClO4
6. H2SO4
7. HNO3

Jessica Chen 1F

Sigma bonds are also stronger than pi bonds, so a double bond (sigma + pi) would overall still be weaker than 2 sigma bonds.

Jessica Chen 1F

Polarizability means that the electron clouds of an atom readily undergo a large distortion. Anions have high polarizability because they are larger and have a bigger electron cloud. The nucleus exerts weak control over valence electrons because there is a lower effective nuclear charge and the elec...

Jessica Chen 1F

The graph shows that: If the bond is weaker, the dissociation energy is smaller because it is easier to break apart the bond. If the bond is stronger, the dissociation energy is higher because it is harder to break apart the bond. As the internuclear distance increases, the dissociation energy decre...

Jessica Chen 1F

The molecular structure for I3- is linear and not bent since the formula is AX2E3 (2 attached atoms, 3 electron pairs), the 3 electron pairs will settle on the axial plane and the other two iodine atoms will settle on the equatorial plane, which will form a linear shape.

Jessica Chen 1F

It's impossible to have more than one sigma bond (with one sigma bond, any more bonds would have to be pi bonds). This is because sigma bonds are when orbitals are overlapping head-to-head, and it's impossible to have 2+ lobes pointing at each other and overlapping each other's orbitals in the head-...

Jessica Chen 1F

This means that the electrons in the p-orbitals pair with the electrons of the p-orbital on the other atom and the orbitals overlap in a side-by-side arrangement both on the top and bottom (on each side of the internuclear axis). These pi bonds basically lock the molecule into place so that it is un...

Jessica Chen 1F

Something to add on is that all single bonds are sigma bonds, all double bonds have one sigma and one pi bond, and all triple bonds have one sigma and two pi bonds and so on (all have one sigma, the rest are pi bonds). The sigma bonds allow the molecule to rotate, but the pi bonds are rigid and lock...

Jessica Chen 1F

AX2E3 is linear because all three lone pairs are equatorial, leaving one upper axial and one lower axial atom that forms a linear shape.
AX2E2 is bent because the two lone pairs repel the two atoms (e.g. water molecule).

Jessica Chen 1F

The two lone pairs look like they are next to each other (and therefore closer) when you draw them in 2D, but because it is a tetrahedral shape, all the angles/positions are technically the same distance from each other and it doesn't matter where the two lone pairs are located.

Jessica Chen 1F

I would divide all the moles by the smallest value, and set that small value as x. The other values would then be multiples (not necessarily integer) of x. I would then try to multiply all these multiples of x by a number to get whole numbers. There's really no easy way besides trial and error for t...

Jessica Chen 1F

A permanent dipole moment is when the molecule is polar. The two or more atoms within the molecule must have substantially different electronegativities (one must attract electrons more than the other and becomes more negative while the other becomes positive).

Jessica Chen 1F

Induced dipole implies that before a heavily charged ion came near the original atom, the atom was nonpolar. Even though the atom was nonpolar, it has a cloud of electrons surrounding it. Putting a charged ion near the nonpolar atom disturbs the arrangement of the electrons so that the originally no...

Jessica Chen 1F

V is the # of valence electrons the atom has (look at the periodic table, count over groups from left to right)
L is how many lone electrons that element has on its Lewis structure
S is the number of shared electrons between multiple atoms' Lewis structures

Jessica Chen 1F

Not any wavelength of light can be emitted from the atoms in the lamp because there needs to be a specific amount (quanta) of energy in order to eject an electron from a metal surface. Thus, the wavelength (because it is related to the frequency and thus energy of the atom) also has to be a specific...

Jessica Chen 1F

The general formula for quantum numbers is (n, l, ml, ms).
Since it's the 5s orbital, n=5.
Since it's the s orbital, l=0.
ml would also be 0, and ms would be either +1/2 or -1/2.
(5, 0, 0, +1/2 or -1/2)

Jessica Chen 1F

Given that an Au atom (gold) has an electron configuration of [Xe] 5d9, 6s2, does that mean the 6s subshell would start to be filled before the 5d subshell was completely filled? Is that possible and why?

Jessica Chen 1F

deltap x deltax >= h/4pi

p (momentum) - kg x m/s
x (position) - m

Jessica Chen 1F

P-orbitals do have one plane!
And d-orbitals have 2 nodes no matter the orientation. Four of the d-orbitals have 2 nodal planes, and one of them has 2 nodes that are actually two cones that point at the origin.

Jessica Chen 1F

You can determine how many values of Ml there are based on the number of L through the equation M = (2L + 1) For example, if L = 1, there are (2(1)+1) = 3 values of M and they are -1, 0, +1 if L = 2, there are (2(2)+1) = 5 values of M and they are -2, -1, 0, +1, +2 and so on.

Jessica Chen 1F

Actually, you can use DeBroglie's equation on photons. Even though photons have no rest mass, they do have a nonzero momentum. Thus, the wavelength relationship still works for photons, you just have to use their momentum and the equation λ=h/p for photons.

Jessica Chen 1F

I asked Prof. Lavelle last lecture and he said the Heisenberg module is the last one he will be posting. No more posts but he did say that Sapling Learning (something that comes with the textbook) has more resources like videos.

Jessica Chen 1F

Threshold energy is the minimum amount of energy needed for the photon to remove an electron from the metal surface. It takes energy for the photon to remove the electron, and any less energy than needed (the threshold) would not eject an electron.

Jessica Chen 1F

In the experiment setup, the detector is connected to a polarized electric circuit, meaning there is a positive end and a negative end. Even though the velocity of the electron is 0, it would float up towards the positively charged part of the circuit near the detector (because opposite charges attr...

Jessica Chen 1F

Usually, if you were given the equation E=1/2MV^2, you would be asked to find V. The M in this equation is the mass of a single electron (not the sum mass of all the electrons), which is the same for all elements no matter the type of element/metal. So yes, it would have to be given and it is 9.11x1...

Jessica Chen 1F

The audio-visual assignments are not part of the homework grade (they are anonymous and the TAs/prof can't keep track of whether you complete them or not, but they are probably helpful in terms of helping you understand the content and doing better on tests!

Jessica Chen 1F

The answer should have as many sigfigs as the LEAST # of sigfigs in the given problem.

For example, if you were told to subtract 1.702 (4 sigfigs) from 5.0 (2 sigfigs), your answer should only have 2 sigfigs and is 3.3.

Jessica Chen 1F

I think Prof.Lavelle did say in a recent lecture that we should include state symbols when writing chemical equations in the homework as well as tests! I'm pretty sure he also said that there won't be a super random compound that we'll have know the state of--it'll generally be something we're famil...

Jessica Chen 1F

Hey! So you can first list out the basic formulas needed here: M(molarity) = mol/volume(L) MiVi=MfVf (because the # of moles are constant; i means initial, f means final) You can then list out the given information: Mi = 0.778 M Vi = ? Mf = 0.0234 M Vf = 150.0 mL You just have to plug all the given ...

Search found 61 matches