CHEMISTRY COMMUNITY

isha dis3d

What is the show cesium and iodine love watching together?
CSI

isha dis3d

How about the chemical workers… are they unionized?

isha dis3d

If you have a chemistry problem where a gas expands in volume AND temperature and were asked to calculate entropy, would you first solve the problem using the equation for two different volumes, and then assume volume is constant and calculate the entropy for two separate temperatures and add them?

isha dis3d

Could someone please explain how you would read a shorthand notation for a voltaic cell that has more than 4 molecules in its notation.

isha dis3d

How do you find the most strongly reducing metal when given a series of metals?

isha dis3d

What should you do if no one laughs at your chemistry jokes?
Keep telling them until you get a reaction.

isha dis3d

What is the chemical formula for "banana"? BaNa2

isha dis3d

You should add the two values together since you flipped the sign for one of the half-reactions. Doing so will result in a positive voltage. Remembering that the voltage should always be positive helps remember which sign to make the reactions.

isha dis3d

All the equations with dt represents differential rate laws, where it depicts rate versus concentration, but the integrated rate law is what shows rate versus time.

isha dis3d

It is however many times you need to divide the larger concentration to get to the second one. You could see this up as [larger concentration]/ 2^x =[lower concentration], and solve for x.

isha dis3d

The optimist sees the glass half full.
The pessimist sees the glass half empty.
The chemist see the glass completely full, half in the liquid state and half in the vapor state.

isha dis3d

The curves dont cross eachother since they have two different pressures at equillibrium.

isha dis3d

Since in PV=nRT, pressure and volume have an inverse relationship, so you can replace V2 and V1 with P2 and P1.

isha dis3d

Q is the energy transfer due to thermal reactions such as heating water, cooking, etc. anywhere where there is a heat transfer. H, is the state of the system, the total heat content.

isha dis3d

In order to balance a redox reaction, you would follow these steps: 1. Balance elements in the equation other than O and H. 2. Balance the oxygen atoms by adding H2O molecules to the opposite side of the equation. 3. Balance the hydrogen atoms by adding H+ ions. 4. Add up the charges on each side an...

isha dis3d

Have you heard the one about a chemist who was reading a book about helium? He just couldn't put it down.

isha dis3d

Cv and Cp are used when there are constant volume and constant pressure, respectively, when the temperature is changing. I believe you use the table which states CV an CP for either atoms, linear, or non-linear molecules.

isha dis3d

Would this mean that the delta S surroundings is -nRln (V2/V1) or -nRln (P2/P1) ?

isha dis3d

This law is also what dignifies the statement delta S total= S surroundings +S system.

isha dis3d

If the volume changes but is at constant pressure, does that automatically make the work of expansion w=-Px (delta) V?

isha dis3d

Silver walks up to Gold in a bar and says, "AU, get outta here!"

isha dis3d

To do this problem, you would need to convert 1 mole of TNT into grams, then use density to convert grams to cm cubed, then use the conversion that 1 L is =1000 cm^3. Divide -67 kj by this number and you would have enthalpy change per liter.

isha dis3d

This is correct since we know that if Q<K, the reaction will favor the products and therefore occur spontaneously since that is the way it moves toward. When Q is greater than K, the reaction will favor the reactants and therefore need the energy to move in the forward direction.

isha dis3d

Calculate the standard molar entropy of vaporization of water at 28.0 °C, given that its standard molar entropy of vaporization at 100.0 °C is 109.0 J⋅K−1⋅mol−1 and the molar heat capacities at constant pressure for liquid water and water vapor are 75.3 J⋅K−1⋅mol−1 and 33.6 J⋅K−1⋅mol−1 , respectivel...

isha dis3d

This is kind of an expansion to the first post, but when exactly would you use each equation?

isha dis3d

The -P delta V equation is used when volume changes in an irreversible reaction, where the external pressure is constant I believe.

isha dis3d

What do chemists call a benzene ring with iron atoms replacing the carbon atoms? A ferrous wheel.

isha dis3d

You could use both these equations when solving for the change in the equilibrium constant, Keq, of a chemical reaction given change in temperature, T, given the standard enthalpy change, ΔH⊖, for the process.

isha dis3d

The formula for delta U has delta H in it, as it is delta U= deltaH -P(delta V)

isha dis3d

Since these images show the same flask over time, the reaction that would be at equilibrium would be the one that has the forward and backward reaction occurring at the same rate. Since the forward reaction increases the number of moles, we know that as time goes on the number of molecules increasin...

isha dis3d

H2O is water and H2O2 is hydrogen peroxide. What is H2O4?
Drinking.

isha dis3d

A higher Kc means that the equilibrium ratio of products to reactants will be higher than at a lower Kc. Therefore it is said to "favor the right", since it has a greater proportion these products.

isha dis3d

Since H2SO4 is a polyprotic and strong acid, you can assume that the first deprotonation ionizes completely, which is why the ICE table directly plugs in the concentration for the second deprotonation .

isha dis3d

In a problem like this, you would use the equation delta (G)= -RTlnK + RTlnQ, where K is given, and Q is the formula we learned to use in equilibrium, where in this case would be ([P i]^2/ [Pi2])

isha dis3d

In the lecture today, Dr. Lavelle mentioned that reversible reactions do more work than non-reversible ones. Could someone please explain why this is so?

isha dis3d

Why did the noble gas cry? Because all his friends argon.

isha dis3d

You add up the values of the enthalpies and "cancel" out the reactants if those reactants are the same as those on the product side of another equation. If in case the coefficients are different, the equations can be combined algebraically. If one side of a reaction had say, 4H2 on the rea...

isha dis3d

I think that state is state property since it doesn't matter the pathway that the chemical takes to get to that phase.

isha dis3d

I think for an ideal gas at constant pressure, it takes more heat to achieve the same temperature change than it does at constant volume. At constant volume all the heat added goes into raising the temperature.But at constant pressure some of the heat goes to doing work.

isha dis3d

With gas pressures, you can still set up an ICE table since the K is given in Kp. It would be set up the same way as you would given molarity.

isha dis3d

Have you heard of Boyle's Law? It's a law stating that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature. Now building on top of that, have you ever heard of Cole's Law? It's a salad dish of raw cabbage, carrots, and other vegetables mixed...

isha dis3d

I think pka ad pkb aren't necessarily equal to ph and pOH, but they both will add to 14. If you think about the way Lavelle explains how p is (-log), then we can see how [H30+][OH-]=10^-14 and [Ka][Kb]=10^-14.

isha dis3d

When the pressure is increased, the reaction is going to favor the side with fewer moles. This is because, by the equation PV=nRT, we see that an increase in pressure creates an increase in moles. In order to retain equilibrium, the reaction will favor the side with fewer moles. So no change should ...

isha dis3d

Since we need the concentration (M) for the equation, divide the number of moles by the 3 liters.

isha dis3d

I think this reasoning would be okay as well, since Le Chatilier's principle states that the reaction will always establish equilibrium again it would do so by forming more products. This results in more moles in the same volume, which by the PV=nrT equation shows that the pressure does increase.

isha dis3d

Knowing that breaking of bonds is an endothermic process, that means that heat is a reactant in the process. Therefore with a temperature increase, the system will shift towards where there is less heat, which is the product side.

isha dis3d

I think as long as you remember how to isolate each variable and solve it using the given information, you will be okay.

isha dis3d

With questions like this, it always helps me to immediately make sure all concentrations are given, so I always automatically convert given moles and grams to concentrations. Also, since there are no coefficients other than 1, after setting up the ICE table you would be able to solve an equation for...

isha dis3d

Something that helped me remember is that K is the constant of a certain reaction when it is in equilibrium, but Q is the same formula using products and reactants at any stage of a reaction.

isha dis3d

I believe the reaction quotient Q is the same as the Kc. There was a previous question that asked this on the chemistry community too from a while back, but it seems the reaction quotient Q follows the same rules where you do not take into account solids or liquids.

isha dis3d

Another way to think of it is to rearrange the variables in the equation. We know that moles/volume is concentration, so n/V in this case is concentration. Solving for n/V in PV=nrT shows that concentration is equal to P/(R*T)

isha dis3d

Why do chemists enjoy working with ammonia?
Because it's pretty basic stuff.

isha dis3d

In general, a conjugate base is an anion that can absorb a proton in a chemical reaction. The conjugate acid is a cation that donates the proton or hydrogen in the reaction and loses the proton.

isha dis3d

In general, I believe cations from group 1 and group 2 are considered weak lewis acids and do not generate H3O+, and does not affect the pH, making it nuetral.

isha dis3d

If the salt has the anion of a weak acid, it will make the solution basic. If the salt has a cation of a weak base, it will make the solution acidic.

isha dis3d

If an acid has a more electronegative cation, the acid will more readily lose H+ ions. This is because the resulting anion is more stable, making the two parts ionize more easily, hence increasing the acidity.

isha dis3d

In the lecture, Dr. Lavelle referred to protonated and alkaline solutions, what exactly does this mean?

isha dis3d

I asked the guy sitting next to me if he had any Sodium Hypobromite…
He said NaBrO

isha dis3d

The radial distribution function is the probability distribution to find the center of a particle in a given position at a radial distance r from the center of a reference sphere. I just think the most important part of this concept it knowing that orbitals and wavefunctions are what give us the pro...

isha dis3d

Hi bff so in the stoichiometric problem you would use the chemical equation to find ratios between any two molecules. From there you can use the ratio of moles to convert from moles to grams using molar mass.

isha dis3d

if ligands are bidentate or more they can form a chelate. I believe this means they bind at more than one site.

isha dis3d

Is whether a ligand is mono, bi, or tri dentate dependent on how many lone pairs it has?

isha dis3d

hybrid orbitals have to do with the regions of electron density. In this case, the five regions of electron density mean the hybridization is sp3d.

isha dis3d

I think that we have to know the general formula of ligand names( with the greek prefix) with the transition metal cation and the anion hydrate.

isha dis3d

Two chemists go into a bar. The first one says "I think I'll have an H2O." The second one says "I think I'll have an H2O too" — and he died.

isha dis3d

In lecture, Dr. Lavells referred to many "unhybridized orbitals". How exactly can you identify these?

isha dis3d

After looking into it, it looks like electronegativity cannot be calculated from the number of subatomic particles in an atom. However, using Ionization Energy and Electron Affinity, one can calculate the Electronegativity of an atom using the above equation.

isha dis3d

I had a follow-up question to this discussion thread, is there a maximum number of electrons an expanded octect can accommodate?

isha dis3d

It is also important to note that different electronegativities between elements indicate different "vector" lengths when drawing the dipole moments out. This could result in a net vector or dipole in one direction.

isha dis3d

If a molecule has hydrogen bonds does it mean it has dipole-dipole as well?

isha dis3d

Kind of as a follow-up question, how would you determine which element in a molecule would create a bigger difference in electronegativity? Like when trying to compare two molecules' iconic character?

isha dis3d

What do you call a tooth in a glass of water? One molar solution

isha dis3d

I had a question that came up as I was doing one of the textbook problems. I noticed that the first electron taken out of Cu to become an ion is taken from 4s. Why is this the case, if the electron configuration of NI is [Ar], 3d8, 4s2?

isha dis3d

It isn't always the same, but I have found that usually when a molecule has the same number of electron densities it becomes easy to assume a shape. For example, when an atom has 4 electron densities around it and no lone pairs, the shape is tetrahedral. When there is one lone pair, the topmost atom...

isha dis3d

Why was the mole of oxygen molecules excited when he walked out of the singles bar?
He got Avogadro's number.

isha dis3d

So just to clarify, as the bond numbers increase (etc. single to triple), the number of sigma bonds stay the same and pi and delta increase?

isha dis3d

I believe that any elements past the atomic number 10 can have an expanded octect. This is because we see that when there are 5 or 6 groupson the central atom, d- orbitals are involved which allow octects to expand.

isha dis3d

LDF happens between all molecules I believe, but dipole dipole will happen between polar ones. LDF only happens when symmetric molecules bind or molecules of the same molecular formula bind.

isha dis3d

To add on to the previous comment, I believe you would be able to tell which experimentally derived bond length fits which atom because the length is usually in between the single and double bond lengths, as in the example with CH above.

isha dis3d

I believe if the difference in electronegativity for the atoms in a bond is greater than 0.4, we consider the bond polar. If the difference in electronegativity is less than 0.4, the bond is essentially nonpolar. If the electronegativity difference is greater than 2 it is considered ionic, and if it...

isha dis3d

I think the reason anions that are pulled into the shared region are classified as covalent is because a covalent bond indicates that two electrons are being shared by two molecules and unlike an ionic bond, are completely transferred over to the other molecule. In the shared region, the two electro...

isha dis3d

You could start this by drawing out the lewis structures for the nitrite, nitrate, phosphite, and phosphate ions. Nitrite has the formula NO2, which when drawn out without minimizing formal charges, would have single bonds between both Os and the N, leaving a formal charge of -1 on both Os and a for...

isha dis3d

I believe that if there ever if one electron that is not paired in a molecule it would be considered a radical.

isha dis3d

Just for further explanation, for atoms in the fourth period and beyond, higher d orbitals can be used for additional shared pairs beyond the octet. The energetic cost of using these higher orbitals to accommodate bonding electrons becomes smaller, as shown by the different atomic orbital energies.

isha dis3d

If two resonance structures have a mirror image of eachother (have the same outer atoms connected to it), are they still considered two different resonance structures or can they be considered the same?

isha dis3d

Another trend like this is seen in the l subshells, as you can find the number of subshells using 2l+1. For example, when l is 1, there are three subshells(2*1+1), -1, 0 and 1. when l is 2, there are five subshells(2*2+1), -2,-1, 0 and 1 and 2.

isha dis3d

An easy way to remember it is that as you go down a group, additional levels of shells are added, which adds tangible size to the atom. Across a period, the atomic radii decreases because as more electrons are added in the same shell, the effective nuclear charge, or Zeff, increases. This is the opp...

isha dis3d

Ionic bonds are stronger than covalent bonds because the electronegativity difference between the two elements is much greater than that of two elements in a covalent bond. In a covalent bond electrons are shared between the two elements and will often favor one element over the other depending on p...

isha dis3d

The same is true for period 5 as it shows the same trend. for example, the electron configuration of silver is [Kr] 4d¹⁰ 5s¹ and the configuration for molybdenum is [Kr] 4d₅ 5s₁.

isha dis3d

Hund's rule tells us about how the electrons in an atom should be placed into degenerate orbitals and is important for distinguishing characteristics of bonding because of how the electrons are placed.

isha dis3d

Could someone please explain the conceptual significance of the derivation of the DeBroglie particle equation?

isha dis3d

The general process I use to find empirical formulas from combustion is as follows: 1. Balance the combustion reaction, 2. Convert CO2 and H2O to moles. 3. convert moles of co2 and h20 into moles of c and h, respectively, and convert into grams of each element. 3. Subtract sum of grams of C and H fr...

isha dis3d

The group 5 elements have five valence electrons in their highest-energy orbitals so they can form ionic compounds by gaining three electrons, forming anions, but I believe they more frequently form compounds through covalent bonding. Bismuth can lose either their outermost p electrons to form 3+ ch...

isha dis3d

Once the frequency of the light exceeds the threshold frequency, photoemission begins. I did some more research regarding this and found Plank's quantum hypothesis, which states that the vibrational energy of atoms in a solid is not continuous but has only discrete values, which I believe would mean...

isha dis3d

Schrodinger's equation is important because wavefunctions of certain electrons are obtained as solutions to this equation. For example, atomic orbitals would be one.

isha dis3d

The second part of the question is basically asking how many electrons will be ejected when the energy of each photon is equal to the work function. This occurs when the kinetic energy of the electrons is zero. You would divide the given 7.21 x 10^-7 J by the found work function to find the number o...

isha dis3d

I saw on the chemistry outline for the Quantum World there was one point that states: With respect to electron transitions that give rise to a UV or visible spectrum: understand the difference between electronic transitions in atomic orbitals (atomic spectroscopy) and electronic transitions in molec...

isha dis3d

Hi, we did this problem in discussion today but I missed the answers. For part a) I ended up getting 0.0423 moles and I was wondering why I got a different answer than posted above? I multiplied 8.61 g * (1 mol/ 202.484 g/mol). I got 202.484 g/mol by adding up the molar mass. I think it has to do w...

isha dis3d

So I was curious regarding this concept after the module as well and after doing some research I found that atomic emission spectroscopy uses transfer and differences in transfers of wavelengths to see how much was absorbed. It does go off of the fact that the wavelengths that are mitted are recorde...

isha dis3d

An easy way to remember that electrons behave as particles in the photoelectric experiment is to remember that when intensity of light was increased, it did not help to remove any more electrons from the metal. Here, increasing intensity of light increased the wavelength which had no effect on the e...

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