CHEMISTRY COMMUNITY

Jonathan Pai 2I

Is water omitted in rate laws in aqueous solutions because the concentration of water is basically doesn't change because it is the solvent???

Jonathan Pai 2I

Why is initial rate against [A] for a 1st Order linear?

Why is half life against [A] for 0th Order linear?

Jonathan Pai 2I

Frequency when molecules collide with good orientation and energy to induce a reaction.

Jonathan Pai 2I

What concepts or problems could combine these two concepts and what the result be? Like temperature effects on rate, thermo equations that can be solved to provide info for kinetic equations?

Jonathan Pai 2I

Only the side that still needs a functional electrode. Just because it has a solid in the reaction does not mean it is an electrode, because it could be just a salt, which you would still need an electrode.

Jonathan Pai 2I

Galvanic cells need to be spontaneous, so that's why it is positive. Electrolytic can be negative because they work in the reverse direction.

Jonathan Pai 2I

Thanks

Jonathan Pai 2I

Yeah, when given energy values, it means per mole or if it of a reaction then it is per reaction.

Jonathan Pai 2I

Catalysts are not included.

Jonathan Pai 2I

Final exam info is on the website link that includes final exam info.

Jonathan Pai 2I

How do we set up Q in a concentration cell?

Jonathan Pai 2I

They are all linear, but 0th is [A], 1st is ln[A], 2nd is 1/[A]. It is that way to linearize the graph, and second order have a positive k slope.

Jonathan Pai 2I

There can be multiple lower case k's depending on how many elementary steps there are.

Jonathan Pai 2I

A first order problem asks to find k, so we used ln[A]=-kt+ln[A]o, but in the solution ignore the negative k value. I thought k could be negative because dont 1st and 0th order have negative slopes in their graph. Do we ignore the negative or how does this work?

Jonathan Pai 2I

The temperature is given to show why the reaction will occur (because of a temperature change), but regarding solving the kinematics and what we need to do, it is unnecessary.

Jonathan Pai 2I

Will we need to know certain industrial and biological processes like rusting or cathodic protection on the FInal? If so, how in depth, like would the scenarios provide us with the chemical reactions, so we won't need to memorize them?

Jonathan Pai 2I

In electrochemical problems like nernst involving n, the transfer of electrons, does that affect the final answer's signifcant figures, because that would make all the final answers 1 sig fig?

Jonathan Pai 2I

The vant hoff equation can be rearranged to find different values, such as G values, enthalpy, entropy, temperature, and K values

Jonathan Pai 2I

There is no curve

Jonathan Pai 2I

H+ is included if it is need in the half cell to balance out the hydrogen, or else the half cell reaction wouldn't happen.

Jonathan Pai 2I

You need Pt if there is not a solid electrode present.

Jonathan Pai 2I

When a conductor is not present. Know that if there is a solid,it does not mean it is automatically a conductor, because some solids are salts,so the Pt will still be needed.

Jonathan Pai 2I

Nernst, electrolytic, and kinetics should work

Jonathan Pai 2I

E is an intensive property, so it doesn't matter how many reactions or the ratio's of it. But reversing does affect if it is positive or negative.

Jonathan Pai 2I

In a cell diagram, knowing that the anode is the left side and cathode is the right side, on each respective side, does the order of the substances matter?

For example, is there a difference between these,
Zn/Zn2+//Ni2+/Ni versus Zn2+/Zn//Ni2+/Ni

Jonathan Pai 2I

Is the anode always reversed to get the full balanced equation? I thought we wanted the most positive voltage everytime, if not then what was that too?

Jonathan Pai 2I

How do you find n in deltaG=-nFE

Jonathan Pai 2I

Use H20 to first balance the oxygen, then use H+ to balance the hydrogens, the e- to balance the charge

Jonathan Pai 2I

Things with less energy are more stable, stuff with more energy are less stable. So if G is positive, that means energy is going up and it's less stable, versus if it was negative then it would become more stable.

Jonathan Pai 2I

Understand the purposes of the parts of the galvanic cells.

Jonathan Pai 2I

The reason the cell potential would be affected because with the salt bridge allowing the ion transfer, then there would be a charge buildup, thus affecting the negatively charged electrons.

Jonathan Pai 2I

yeah it's the equilibrium constant

Jonathan Pai 2I

All chemical things want to go to a lower energy, so exothermics release energy, that is why it is spontaneous.

Jonathan Pai 2I

reversible happens slowly so heat change can occur and the pressure usually is changing

Jonathan Pai 2I

yes, it involves enthalpy and temperature

Jonathan Pai 2I

isolated system transfers no matter or energy, so deltaU is 0, however U can have a specific value.

Jonathan Pai 2I

using which R depends on if the answer is looking for joules or looking for something else, like liters per mol. But, you can always convert after using 101.325 to get the correct units and value

Jonathan Pai 2I

the numerical values will have the little dot showing it is standard

Jonathan Pai 2I

complexity of the molecule effects entropy

Jonathan Pai 2I

irreversable needs to occur slowly for heat to equal out and pressure

Jonathan Pai 2I

I thought the main point of reversible was a changing pressure, but a homework problem asks us to solve a reversible at constant pressure. Can you explain the relationship between reversible and pressure.

Jonathan Pai 2I

Why does q=(C)(deltaT) for the q of a calorimeter. Why can we omit moles, n, from the equation when dealing with heat transfer with the calorimeter.

Jonathan Pai 2I

We are provided the constants and equations. Ones specific for this chapter are the ideal gas constants, ideal gas law, heat, the two work equations, etc.

Jonathan Pai 2I

Why does deltaH=q at constant pressure?

Why does deltaH=q at constant volume?

Thanks CC

Jonathan Pai 2I

Why is a motor engine and a body considered open systems?

Jonathan Pai 2I

Think of how we looked at endothermic reactions in equilibrium and boiling water. If you boil water (add heat), what happens. Water vapor is formed (product), so the added heat from the stove created more products, which is the characteristic of an endothermic reaction. H2O(l) + heat <> H2O(g) , shi...

Jonathan Pai 2I

A table will be given in the book. Sometimes though it will give us the K value for the conjugate base/acid, so we would need to manipulate Kw=Ka*Kb.

Jonathan Pai 2I

When the k value is small, 10^-3 , because so little of the reactants go to products it is negligable.

Jonathan Pai 2I

In 6D15, why does the AlCl3 become Al(H2O)^6 in the chemical equation, why doesn't it just become Al^3+, and why would it get 6 water molecules? And where was the Ka value provided? Thanks.

Jonathan Pai 2I

If it contains one more or less H, and the other atoms are the same. in the 6C1 table, they are there, the conjugate would be slightly different and would have the other Ka or Kb, depending if it is a conjugate acid or base.

Jonathan Pai 2I

There is no equilibrium change because the concentration of the gases at interest have not changed. Neither the n nor V have changed.

Jonathan Pai 2I

The K value is same though.

Jonathan Pai 2I

Ka*Kb = Kw

Kw is always 1.0x10^-14, so is one value increases, the other decreases.

Jonathan Pai 2I

K uses only equilibrium concentrations. Q can use any concentration at any time, which tells us where the reaction will go.

Jonathan Pai 2I

Use the one your given, don't use the one your not given.

Jonathan Pai 2I

Stability also relates to exo or endo, such as the HW question using a halogen, which makes us have to know that halogens are stable diatomically, so dissociating to monotomic would have to be endothermic.

Jonathan Pai 2I

Everything is assumed to remain the same unless it is explicitly stated.

Jonathan Pai 2I

Unaffected

Jonathan Pai 2I

It has -ate either because the hexcyanidochromate(III) part, the complex, is negative or because the chromium had just eaten.

Jonathan Pai 2I

Lone pairs or unfilled octet. Or if it's got extra H's or OH's.

Jonathan Pai 2I

Depends if it loses or accepts and H.

Jonathan Pai 2I

Lit is smaller so it has stronger polarizing power. You might be confusing poloarizing power with polarizability.

Jonathan Pai 2I

Jonathan Pai 2I

It means hybridization comes from atomic orbitals.

The orbitals hybridize so they can have more orbitals and a different shape that is necessary to form a bond.

Jonathan Pai 2I

For example, if molecule X has 2 double bonds and 1 single and molecule Y has 1 double bond and 2 single bonds, Molecule Y is longer because the averages are longer.

Jonathan Pai 2I

For sure

Jonathan Pai 2I

Octahedral is 90* between any atom, that's why it doesn't matter. But Trig Bipyr has angles of 90*(axial to equatorials) and 120*(trig planar atoms), that's why LP placement matters in Trig Bipyr.

Jonathan Pai 2I

A good reminder is the tail of the arrow having a perpendicular line to represent the addition symbol, +, thus showing that is the positive side going towards the negative part.

Jonathan Pai 2I

Yes it depends on IMF's.

From those it looks like LiCl is ionic, C3H7OH is H Bonding, C4H8 is nonpolar Londons, and N2 is also nonpolar but I think weaker than C4H8 because it has less electrons, so less London strength.

Correct me if I'm wrong.

Jonathan Pai 2I

I believe Sigma and Pie bonds aren't meant to describe the actual thing, such as resonance being an average of the bond lengths, but instead describing how we describe bonded molecules as single, double, triple bonds.

Jonathan Pai 2I

Are London forces a characteristic of all molecules, even polar molecules?

Jonathan Pai 2I

Dipole Dipole is molecules having a concentration of charge in a certain area due to polarity, which allows for greater attraction with another molecule that has its charges concentrated in certain areas. Hydrogen bonding is just super strong Dipole Dipole because of the Hydrogen with very electrone...

Jonathan Pai 2I

Jonathan Pai 2I

Sigma's bond along the same orientation axis. Pie bonds don't, so there is no rotation. Pie bonds are weaker than Sigma bonds because they don't have overlap, so weaker attraction

Jonathan Pai 2I

What is the difference? What terms are used to describe each one?

Jonathan Pai 2I

If it was in axial position, it would be repelling with 3 atoms at 90 degrees, because all 3 equatorial atoms would be there. Because it is in the equatorial position, it is only 90 degrees with 2 atoms, the axial ones.

Jonathan Pai 2I

Why does higher polarity lead to higher boiling point???

Jonathan Pai 2I

Is water's polarity the reason salts dissolve.

Jonathan Pai 2I

Think of H bonded to Phone, b/c it sounds like FON, is Hydrogen Bonding

Jonathan Pai 2I

I think it's Potential Energy of the London interaction between different molecules. The potential energy decreases very rapidly with distance increase because it is r^6.

Jonathan Pai 2I

Qualitative differences prob. Maybe why a double bond isn't twice as strong as a single bond, because Pie bond is weaker than Sigma bond.

Jonathan Pai 2I

Because Pie bonds don't overlap like Sigma bonds, they are weaker than Sigma bonds. That's why double bonds are less than twice as strong as single bond.

Jonathan Pai 2I

Formal charge wouldn't work out either

Jonathan Pai 2I

Some arrows have a plus sign, +, on the tail showing positive and then point of arrow is going to negative

Jonathan Pai 2I

It's good to know about the 2 and 1.5 values, but understanding why is a better plan. Given ionic bonds have large electronegativity differences, of course they'll be greater than 2, so knowing bonds that are of an atom on the left and right of periodic table, thus large electronegativity difference...

Jonathan Pai 2I

Trigonal Bipyramidal is like a totally blended version of linear, axial, and trigonal planar, equatorial.

Jonathan Pai 2I

Why is CH2Cl2 polar, I was thinking them H's would cancel each other and them Cl's would cancel each other. This problem 2E25D.

Thanks CC squad!

Jonathan Pai 2I

T-Shape is formed by 5 regions of electron density, which is the trigonal bipyramidal. Trigonal Bipyramidal is 3 equatorial bonds, 120* apart essentially making a trigonal planar, and 2 axial bonds, forming the top point of each pyramid and 90* from each of the equatorial atoms. The reason it forms ...

Jonathan Pai 2I

dipole is a concentration of charge, thus unbalancing the charge in an atom.

Jonathan Pai 2I

I think energy of breaking the bonds

Jonathan Pai 2I

Yes, because it has the same 3 Dimensional shape as a tetrahedral, however because of the lone pair, its shape is "Trigonal Pyramidal"

Jonathan Pai 2I

Sarah, you're right that N3- is bigger than O2-, which is why it has more polarizability, because there is more space for charge to concentrate in. You may be confusing the concept of polarizing power, which is question 2D9.

Jonathan Pai 2I

If charges favor a certain area more than any other area, it is polar. So usually if there is a lone pair hanging out polarity may occur because the lone pair pushes the bonds away more than a typical bond, thus the charges from the bonds are in a tighter local, thus not as equally spread out.

Jonathan Pai 2I

Google it, Or Bing it ;), what an octahedron looks like. Outside atoms form the points of an octahedron.

Jonathan Pai 2I

The wide balloon effect of Lone Pairs may help you visualize why it pushes the bonds closer, thus decreasing the angles.

Jonathan Pai 2I

Whip out your ruler and check.

We don't need to how to get bond lengths, just understand the relationship between strength, length, and single, double, triple, or james bonds.

Jonathan Pai 2I

Lewis structures do not have to be drawn like its shape because in the complex shapes it would be difficult and pointless to try to replicate the 3D shape in 2D. That's why knowing the name and bond angle is important in order to specify.

Jonathan Pai 2I

Resonance shows where the least concentration of charge will look like. But in reality, resonance structures are "averaged out". For example a thing with 2 single and 1 double bond is actually like 3 1.33 bonds.

Jonathan Pai 2I

The second is a simplified version of the deltaE version of the first one. DeltaE being it is set up as final-initial. The first one shows how the energy is related to the concept, the second one does not.

Jonathan Pai 2I

No, it the photon just passes right through. This can be understood through conservation of energy. The "input" photon which excites the electron must be the same value of the "output" photon when the electron drops. So it won't happen if it's 2.5, where 2 will input and the .5 w...

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