CHEMISTRY COMMUNITY

Reva Kakaria 1J

A second order reaction means that the reaction rate is proportional to either the square of the concentration of one reactant, or to the concentrations of two reactants multiplied together; so two molecules have to collide for the reaction.

Reva Kakaria 1J

Given the elementary steps of a reaction mechanism, how are you supposed to figure out which one is the rate-determining/slow step? What kind of information would have to be given to be able to know?

Reva Kakaria 1J

Since it isn't in the syllabus, I don't think we need to know it.

Reva Kakaria 1J

The frequency factor represents how often molecules collide in the correct orientation for a reaction to occur.

Reva Kakaria 1J

A metal is corroded when it loses electrons (it's oxidized). These electrons are conducted to a cathode, which is then reduced, and gets plated.

Reva Kakaria 1J

I think this week's homework should be mainly kinetics problems since we started covering kinetics last week.

Reva Kakaria 1J

Yes, I believe first order reaction graphs will always be straight lines when they are graphed as ln[R] vs time.

Reva Kakaria 1J

I think they probably want us to use the elements in their most stable form, which for carbon is C (s), graphite.

Reva Kakaria 1J

Since K is equal to concentration of products over concentration reactants, if one of the reactant's concentration is quadrupled, then the the original K is divided by 4.

Reva Kakaria 1J

This is similar to the Hess's Law approach we used for calculating reaction enthalpy. Basically, you want to make sure that the substances you are not interested in cancel each other out. In this case, you are trying to find the Gibbs Free Energy of ATP hydrolysis, and therefore want to cancel out t...

Reva Kakaria 1J

Yes, if delta G is positive, the reaction is always not spontaneous.

Reva Kakaria 1J

The lecture in which we started Gibbs free energy was on 2/8, right after we finished entropy, so I would start from there excluding the entropy material.

Reva Kakaria 1J

It might be because the 1 mL = 1 gram is only applicable for water, not for other substances.

Reva Kakaria 1J

005199302 wrote:for #6, how do we know that change in entropy is zero?

Since the system starts and ends at the same state, the entropy doesn't change.

Reva Kakaria 1J

I am still confused as to what exactly the difference between degeneracy and entropy? Don't both of these concepts relate to disorder in a system? While both of them relate to disorder, degeneracy is just the number of states a system has that are the same energy level. Entropy, however, is the deg...

Reva Kakaria 1J

If the reaction is endothermic, then cooling will favor reactant formation; if the reactant is exothermic, then cooling will favor product formation. This occurs according to Le Châtelier's Principle, since the systems will adjust to minimize the temperature change.

Reva Kakaria 1J

Basically, degeneracy is the number of states in which energy can be at a given level. If a given particle can only be at a certain energy level in one particular state (i.e. if it moves, its energy level changes), then it has a degeneracy of 1. Going back to the example Professor Lavelle gave in cl...

Reva Kakaria 1J

They're available to pick up in Young 3034! You just have to show your bruin card and then you can get your final.

Reva Kakaria 1J

Could someone please explain why reversible expansion must be isothermic?

Reva Kakaria 1J

An extensive property is something that depends on how much of something is being measured, like mass, which changes depending on how much of a substance you weigh. An intensive property doesn't depend on the amount of substance; for example, density remains the same throughout some substance no mat...

Reva Kakaria 1J

In a bomb calorimeter, volume is kept constant, so pressure changes; in the other type of calorimeter, pressure is kept constant, so volume can change.

Reva Kakaria 1J

Enthalpy is the amount of heat released or absorbed in some reaction at a constant pressure, whereas heat capacity is the heat required to raise the temperature of some substance by 1 degree Celsius. In both cases, the units to use are Celsius or Kelvin.

Reva Kakaria 1J

I believe it is the concentration of the conjugate acid over the initial concentration of the base multiplied by 100.

Reva Kakaria 1J

Yes, since strong acids and bases are 100% ionized.

Reva Kakaria 1J

Yes, salts will be included on the test (everything up to last Friday will be on the test).

Reva Kakaria 1J

In lecture, Dr. Lavelle stated that the ionization constant of water is Kw = [H3O+][OH-] = 10^-14. What exactly does ionization constant mean? Is it the same thing as equilibrium constant?

Reva Kakaria 1J

I would recommend doing as many practice problems from the textbook from different topics as you feel necessary for your own understanding. There are also weekly review worksheets on Chemistry Community (if you search "Session Worksheets" you should be able to find them). If you feel like ...

Reva Kakaria 1J

As long as you keep the units consistent throughout a single problem, you can use both bars and atm to calculate Kp, depending on which one is given in a problem.

Reva Kakaria 1J

A spontaneous reaction is a reaction that takes place without any external interference; a spontaneous reaction is exothermic (there is a decrease of energy in the system).

Reva Kakaria 1J

For units of partial pressure, should we use bars or atmospheres? What is the difference between the two?

Reva Kakaria 1J

I believe it depends on what you are given: if you are given the concentrations of the molecules in the chemical reaction, then it's Kc, and if you are given the partial pressures, you have to find Kp.

Reva Kakaria 1J

When a compound has resonance structures, its negative charge/electrons are delocalized. This makes it more stable, so if that compound has a bond with H, it is more likely to lose H+ since the resulting anion will be stabilized by delocalization. In other words, the more stable the anion is, the mo...

Reva Kakaria 1J

Drawing the most stable Lewis structure is probably the best way to go about it, because it will give you the correct answer every time if it is drawn correctly.

Reva Kakaria 1J

Amphoteric refers to a compound, especially metal oxides/hydroxides, that can act as either a base or an acid.

Reva Kakaria 1J

A coordinate covalent bond is a covalent bond in which two of the electrons come from a single atom. Hope this helps!

Reva Kakaria 1J

The end of outline 3, which is chemical bonds, and all of outline 4 (molecular shape and structure).

Reva Kakaria 1J

CLO2+ has three regions of electron density (one lone pair and two double bonds), but since the name of the shape of a compound is only based on bonds and excludes lone pairs, its shape is angular/bent. In terms of electron density regions, however, it is trigonal planar.

Reva Kakaria 1J

Since H3O+ has a lone pair and three bonds, I think the bond angles would be <109.5 degrees, since the electron densities are tetrahedral, but a lone pair is more diffuse than a bond so it pushes the covalent bonds closer together.

Reva Kakaria 1J

Basically, we name molecule shapes based on the number of bonds they have, not based on the number of regions of electron density. So in terms of regions of electron density, ammonia is tetrahedral because there is one lone pair and three bonds (so four areas of electron density), but since we only ...

Reva Kakaria 1J

Yes, bent and angular both describe the same molecular shape!

Reva Kakaria 1J

Enzymes and proteins have active sites which other molecules bind to; they are then converted into some product and released. The shape of an enzyme's active site, which is influenced by electronic structure, determines what kind of molecules can attach to it, and therefore what the function of that...

Reva Kakaria 1J

It results in momentary areas of relatively high or low electron density, causing nearby atoms to be attracted to the positive area, which is how Van Der Waals forces are created.

Reva Kakaria 1J

Distortion is when the shape of the electron cloud of an atom is changed due to attraction from another atom. If an atom is highly polarizable, that means that its electron cloud can be distorted easily by a polarizing atom.

Reva Kakaria 1J

Multiplying the percentage by the molar mass is more accurate and faster than assuming 100g and converting that into moles, and then dividing by the smallest number. You can then use the grams found by multiplying percentage by molar mass to convert into moles, which gives you the molecular formula,...

Reva Kakaria 1J

Since MgCl2 is a salt, I believe you would draw it similar to NH4Cl, by putting Mg in the middle with full octet in brackets and one Cl- on either side without any dots for electrons.

Reva Kakaria 1J

You should add a double bond if it lowers the formal charges, since the most stable Lewis structure for a molecule is the one with the smallest formal charges on each atom. The number of bonds depends on which specific Lewis structure you're drawing, but in general you should never have more than th...

Reva Kakaria 1J

Double bonds are shorter because they share more electrons, attracting the nuclei of two atoms closer together than a single bond does.

Reva Kakaria 1J

None of the resonance structures we draw as Lewis symbols actually exist in real life, because in an actual molecule that has resonance structures, the double bond is divided up in between the atoms equally. For example, for a nitrate ion, NO3-, we draw the Lewis structure as nitrogen having a doubl...

Reva Kakaria 1J

Yes, I believe when an object is large its uncertainty is so small in comparison that it's basically irrelevant to calculations done

Reva Kakaria 1J

I think it's a convention, because when an electron's energy is zero, it's on the verge of escaping from the atom. If the electron is closer to the negative, it has less potential energy, so it becomes negative. The negative sign lets us differentiate between attached electrons and free electrons; t...

Reva Kakaria 1J

A black body is a theoretical object that absorbs all wavelengths of radiation. When an object is heated up, it emits light, so black-body radiation is the wavelengths of light a black body emits when heated up. Observation of black-body radiation has shown that the intensity of the radiation emitte...

Reva Kakaria 1J

When we're given ∆x, it's usually the diameter of an atom, but one of the problems in the book uses diameter of a nanoparticle. I think in general we will be given some sort of diameter.

Reva Kakaria 1J

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. Answer the following three questions. A. What is the kinetic energy of the ejected electron? How would one go about to solve this problem? What equation wo...

Reva Kakaria 1J

The answer is C, the extent of the change in the electrical field at a given point decreases, because since E =hv, when frequency decreases, so does energy. Less energy means less of a change in the electrical field. Hope this helps!

Reva Kakaria 1J

natalieg4e wrote:Will this equation be provided on the test?

Yes, it's on the constants and equations sheet that we're provided for tests.

Reva Kakaria 1J

I don't think it should matter, since it's just different notation forms of writing them, and g/mol makes dimensional analysis easier

Reva Kakaria 1J

I think you use the Balmer series when n = 2, so electrons are in the second energy level, and the Lyman series when n = 1, so electrons are in ground state.

Reva Kakaria 1J

Hi! The rules of sig figs are: 1. All non-zero digits are significant 2. Any zeros in between two non-zero numbers are significant 3. A zero at the end of a number without a decimal point is not significant 4. Any zeros at the beginning of a number are not significant 5. Final/trailing zeros in a nu...

Reva Kakaria 1J

The molar mass of the molecular formula Xylitol is given as 152.15, and when you add up all the molar masses of C5H12O5, you get the same number, which means that it's the molecular formula. In this case the molecular formula is also the empirical formula, since the amounts of each element are alrea...

Reva Kakaria 1J

If there is no excess of either reactant, that means that all reactants are present in exactly the right molar ratio. This means calculating the moles of product with any reactant would give you the same answer. This works even if they don't have the same number of moles; as long as the ratio is rig...

Reva Kakaria 1J

Hi! When I solve for V using the formula M = n/V, I get V = n/M, so I think you might have accidentally inverted molarity and moles. Then when I do the problem, I get
V = 0.03/0.06, which gives me 0.5 Liters.
I hope this helps!

Reva Kakaria 1J

I think only multiple points can be precise, since precision is defined as a series of measurements being close to each other, and a single point can't do that.

Search found 62 matches