CHEMISTRY COMMUNITY

Ayushi2011

Yes, rate is determine by the slowest step.

Ayushi2011

More T, more activation energy because more collisions.

Ayushi2011

State functions are path-independent.

Ayushi2011

Q is negative as heat is being released.

Ayushi2011

You use the van't hoff equation.

Ayushi2011

Kelvin is always the unit for such equations.

Ayushi2011

I would calculate deltaH and then use deltaG = deltaH - TdeltaS to find entropy.

Ayushi2011

Depends on whether work is done or work is being done on the system.

Ayushi2011

Strong acids dissociate completely, while weak acids don't which affects the ph.

Ayushi2011

Use the 5% rule, if X is less than that then we can approximate.

Ayushi2011

K depended on ADP, basically the same as ADP.

Ayushi2011

Pre equilibrium is probably the method i would use.

Ayushi2011

When the rate is affected by the concentration of two first-order reactants, it is a second order reaction.

Ayushi2011

A catalyst will first appear to the left as a reactant, and then as a product in the following reactions because it speeds up the reaction but doesn't get used up.

Ayushi2011

No, only stoichiometric coeffecients affect the rate of a reaction, not the size of the reactant molecules.

Ayushi2011

It is independent of the concentration of the reactants.

Ayushi2011

A ph meter is a glass electrode, it is an ion-selective electrode.

Ayushi2011

You would do standard potential of cathode minus the standard potential of anode.

Ayushi2011

You use K when the reaction is at equilibrium, and Q when the reaction is not.

Ayushi2011

When a system does work, the value of work is negative.

Ayushi2011

G* means a substance is in its standard state.

Ayushi2011

Use q=mcdeltaT for these problems. Take into account phase changes as well.

Ayushi2011

It relates equilibrium constant to temperature.

Ayushi2011

More the disorganization, more is the entropy which is why COF2 will have more entropy compared to BF3.

Ayushi2011

Do try and read and understand what the textbook says.

Ayushi2011

Yes, because the power will be 1, making it a first order reaction.

Ayushi2011

The slowest step is the rate determining step, if the catalyst doesn't affect this step, the rate of reaction doesn't change.

Ayushi2011

Ayushi2011

They usually tell us which is the slow and fast step.

Ayushi2011

It is introduced as a reactant, and then produced as a product in the following equations showing that it remains unconsumed in the reaction.

Ayushi2011

Since its energy, its unit can be Joules or kJ.

Ayushi2011

A zero order reaction is independent of concentration and only depends on the rate constant.

Ayushi2011

[h3O+] + [OH-] = kw = 1x10^-14

Ayushi2011

Greater than 10^3 is a strong acid.

Ayushi2011

P is the constant pressure and V indicates temperature.

Ayushi2011

If the system is compressed, the reaction proceeds in the direction with the least moles of the gas, which can be either reactants or products.

Ayushi2011

Very strong acids have extremely low PH, sometimes it can be negative.

Ayushi2011

Inert gases won't cause any change in the chemical equilibrium (equilibrium constant) since they are unreactive.

Ayushi2011

We record temperature in terms of how it changes, change in a celsius is same as a change in a kelvin.

Ayushi2011

Breaking a bond is endothermic and forming one is exothermic, so it can be either.

Ayushi2011

If K value is very small, we can approximate.

Ayushi2011

when you are given Ka and Kb, you take -log of that to find pka and pkb. Pka + Pkb = 14

Ayushi2011

Strong acids and bases do have Ka and Kb.

Ayushi2011

To put it in simpler terms, changing the state of a substance releases a lot more energy than the substance remaining in the same state. Water at 100C releases less heat than steam because the change in state from water to steam (vaporisation), releases more energy.

Ayushi2011

Increasing pressure shifts the reaction to the side with the fewer moles of gas according to Le Chatelier's principle.

Ayushi2011

If we assume that the concentrations of h3o+ and oh- is the same, the answer will be square root of kw which is 10^-7.

Ayushi2011

Only gaseous and aqueous substances will be included in the equilibrium constant equations.

Ayushi2011

P stands for pressure, V is volume, n is number of moles, R is ideal gas constant, T is temperature,

Ayushi2011

The principle states that every time there is a shift from equilibrium, the effect of the shift will be counteracted to maintain equilibrium.

Ayushi2011

Kp is equilibrium constant for pressure whereas Kc is for concentrations.

Ayushi2011

Ionic bonds don't form sigma bonds, it is only for shared electrons.

Ayushi2011

Pi bonds only use unhybridized p orbitals.

Ayushi2011

ionic dipole is stronger than hydrogen bonding, so needs a higher melting point in order to break the bonds.

Ayushi2011

The trend is that electronegativity increases as we move across the period and decreases as we move down the group.

Ayushi2011

Non metal oxides generally form acids and metal oxides form strong bases.

Ayushi2011

smaller cations with less electron cloud have higher polarising power whereas larger anions with a large electron cloud and distortion have more polarizability.

Ayushi2011

I don't think resonance has got to do with strength per se. It is more about stabilizing the atom by delocalising the electrons. it also maintains a constant bond length in the compound.

Ayushi2011

Higher the electronegativity of an atom, the more electron it draws, making the acid stronger.

Ayushi2011

We mainly look at regions of electron density rather than bonding or lone pairs, in case of hybridization.

Ayushi2011

I think the hierarchy is ionic>ionic-dipole>hydrogen>dipole-dipole>london forces (in terms of strength of interaction). Higher the strength, higher the temperature it needs to break the bond so higher melting point.

Ayushi2011

I believe resonance stabilises a compound. Strength depends on the length of the bond, and other factors like electron repulsion, radius etc.

Ayushi2011

inter is between two molecules and intra is within the same molecule.

Ayushi2011

Lone pair-lone pair electron repulsion is the highest, so they need to be placed away from each other as we want minimum repulsion for most stability.

Ayushi2011

I think we memorise shapes and bond angles relative to each other, like why would a particular bond angle be smaller than another etc.

Ayushi2011

Regions where electrons are found, as the name suggests, the region where the electrons are most dense around an atom.

Ayushi2011

It covers both, whatever covered after midterm!

Ayushi2011

Bonding pairs have least repulsion, then lone pairs with bonding pairs, and lone pairs with each other have the highest repulsion.

Ayushi2011

Lone pair decreases bond angle because it causes repulsion with other lone pairs and bonding pairs.

Ayushi2011

The arrow points to the atom that pulls electrons towards itself, so the most electronegative one.

Ayushi2011

We name things according to molecular geometry because electron geometry takes into account lone pairs. We don't take lone pairs into account while writing the structure, just to find out how to minimize repulsion.

Ayushi2011

If there is repulsion between lone pairs, it would change the structure of the atom. We need to figure out how the lone pairs need to be arranged in each structure to minimise repulsion and find most stability.

Ayushi2011

This notation lets us know the number of bonding pairs and lone pairs which makes it easier to draw structures.

Ayushi2011

M stands for mega with value 10^6.

Ayushi2011

Won't be tested on the midterm.

Ayushi2011

Generally d-block elements because the d-orbital can accommodate more valence electrons.

Ayushi2011

4s is lower in energy than 3d, causing it to get filled up first.

Ayushi2011

Any particle with wavelike properties that has momentum. They will give us the mass and velocity.

Ayushi2011

We always want to put the least electronegative atom in the center.

Ayushi2011

Adding more electrons would definitely increase the atomic radius because the electrons keep getting added to the outermost shell.

Ayushi2011

A spin quantum number of +1/2 means the spin is in the upward direction, and vice versa for -1/2. Two electrons of opposite spin are always placed in one orbital
(by Hund's rule)

Ayushi2011

Formal charge needs to be calculated. If the formal charge of the central atom is 0, the atom is stable.

Ayushi2011

The mass of an electron will always be given to us, because it is a set mass.

Ayushi2011

You can also determine polarity from structure. If the structure of the compound is symmetric in terms of distribution of elements around the central atom, it is non polar. If the compound has a charge and is asymmetric, it is polar.

Ayushi2011

The unit is Joules, but in relation to photoelectric effect it is Joules per photon, since that is the particle whose energy we're trying to calculate.

Ayushi2011

The value of atomic radius will always be given to us.

Ayushi2011

The equation is used to calculate wavelength of a particle with linear momentum. The equation is wavelength(lambda) = h/m*v where h is Planck's constant (6.626*10^-34 Js) , m = mass of particle, v = velocity with which the particle is moving. the formula could also be lambda = h/p(momentum) as momen...

Ayushi2011

Do use the one given by Dr. Lavelle. Since Rydberg's constant is frequency, the unit is s^-1 or Hz.

Ayushi2011

Do use the one given by Dr. Lavelle. Since Rydberg's constant is frequency, the unit is s^-1 or Hz.

Ayushi2011

It is a unit of energy. 1keV = 1.602 * 10^-16 J. Normally an eV = 1.602 *n10^-19 J but since this is Kilo electron volt, the power to 10 is raised to -16.

Ayushi2011

I think you need to know which series corresponds to which energy level and region (UV, infrared, etc). It might help to go over wavelengths of some of the regions as well.

Ayushi2011

Doesn't hurt to write it down because its just additional helpful information!

Ayushi2011

I had no idea we get 10 points for just being there!

Ayushi2011

hey! You first have to balance the equation = 2AL + 6HCL --> 2ALCL3 + 3H2. You then calculate how many grams of product does each reactant give by calculating molar masses and using molecular weights of each. Using Al, we get: (5.43gAl/26.981g/molAl)*(2mol/2mol)*133.481g/molAlCl3 = 26.86g of AlCl3 D...

Ayushi2011

I'd start by first finding the how many elements are there in the compound, and then find the molecular mass of the compound. Since we know the number of elements, we divide the molecular mass of each element by the total mass of the compound we just found, to get mass percentage.

Ayushi2011

You can do either! I did both just to review all topics.

Ayushi2011

Could someone explain how to find the excess reactant in M5? I'm slightly confused.

Ayushi2011

He specified to do either fundamentals or quantum world or both for Homework 2!

Ayushi2011

He specified to do either fundamentals or quantum world or both for Homework 2!

Ayushi2011

For part b, I'd find the moles of a kilogram of water which is 1000g/(18.02g/mol) which is 55.49 moles. Since 1 mole has 6.022x10^23 molecules, 55.49 moles will have 55.49x(6.023x10^23)molecules which is 3.34x10^25 molecules.

Ayushi2011

What generally works for me is trial and error. I sort of keep multiplying low value numbers until I find one that converts all the decimals into whole numbers, or at least close. It may not be the most efficient way but it definitely does give me the right answer.

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