CHEMISTRY COMMUNITY

melodyzaki2E

The rate constant of the reaction between CO2 and OH in aqueous solution to give the HCO3- ion is 1.5 *10^10 L/mol*s at 25 C. Determine the rate constant at blood temperature (37 C), given that the activation energy for the reaction is 38 kJmol-1.

melodyzaki2E

The rate constant of the first-order reaction 2 N2O(g)--->2 N2(g) + O2(g) is 0.76 1/s at 1000. K and 0.87 1/s at 1030. K.
Calculate the activation energy of the reaction.
How do you use Arrhenius here?

melodyzaki2E

Is the value for Kp given at a different temperature? Maybe use Van't Hoff? Because we don't include solids in our equilibrium constant equations, right?

melodyzaki2E

I'm confused about this too. I think in elementary steps, we can use the coefficients as the exponents for the rate law equation or maybe experimental data?

melodyzaki2E

i think adding up the exponents in the rate law equation gives us the order of the reaction, or we could look at the way concentration changes as time increases (on a graph) ?

melodyzaki2E

doesn't k change in response to changes in the rate of a reaction (so anything that increases or slows down the reaction including temperature, concentration, etc) ?

melodyzaki2E

How do we determine the Rate Law for a reaction when the experimental data isn't clear on what is doubled?

melodyzaki2E

I think the derived ln formula for first order will always be a straight line but I don't think the actual rate law for first order reactions are first order, i'm not totally sure though.

melodyzaki2E

I think for that one you had to solve for the Kw value at the lower temperature and then take the square root of that value to find the H+ concentration. If that value was lower than 10^-7 (which is the H+ concentration at pH of 7) then I think your solution was acidic because you had more H+ than O...

melodyzaki2E

A battery is just a collection of galvanic cells joined in a series and each galvanic cell has an anode and a cathode.

melodyzaki2E

yes, because the K value was large so product formation was favored so products are clearly more stable.

melodyzaki2E

I think we're supposed to use H+ when balancing acidic redox reactions for simplicity.

melodyzaki2E

there's usually a volume change or a change in the number of moles between reactants and products, I think.

melodyzaki2E

entropy is the measure of disorder or random activity in a system, whereas enthalpy is a measure of the overall energy is a system

melodyzaki2E

I think this is when you are calculating the enthalpy of formation of the standard molar entropy for 1 mole of NH3 because then you just want to produce one mole of that product. I'm not totally sure though.

melodyzaki2E

i think this is used when you have to calculate the heat capacity of an ideal gas at a constant volume

melodyzaki2E

in the second equation the pressure is constant and the volume is changing in response so everything on the other side of the ideal gas law equation stays constant, i'm not sure why we don't include it though.

melodyzaki2E

degeneracy is the number of positions a molecule can have raised to the number of molecules/particles in the object you're looking at. the ratio of the change in volume is equal to the change in degeneracy, so if you double the volume the ratio of degeneracy would be 2:1 (final degeneracy over initi...

melodyzaki2E

I think he'll expect us to know how to do it because we went through it in chem 14a. I'm not totally sure though.

melodyzaki2E

I think that's the equation for calculating heat. The equations for specific heat capacity and molar heat capacity include moles and grams I think?

melodyzaki2E

Identify the following systems as open, closed, or isolated: (a) coffee in a very-high-quality thermos bottle; (b) coolant in a refrigerator coil; (c) a bomb calorimeter in which benzene is burned; (d) gasoline burning in an automobile engine; (e) mercury in a thermometer; (f) a living plant. Does a...

melodyzaki2E

I would put each equation on top of each other, then cancel out the products that are used up as reactants in the next step (you may have to multiply to cancel them out exactly), then just add up all the enthalpy changes when you are left with your desired chemical reaction.

melodyzaki2E

when steam hits your skin, a lot of energy will be released as it condenses into a liquid, undergoing a phase change (because your skin temperature is a lot cooler in temperature), this energy release causes a much worse burn than if the same amount of boiling water were to hit your skin where it wo...

melodyzaki2E

work can't be a state function because it is proportional to the distance an object is moved, which depends on the path used to go from the initial to the final state and thus if work isn't a state function, then heat can't be a state function either because according to the first law of thermodynam...

melodyzaki2E

if they increase pressure by adding an inert gas, it doesn't shift the chemical reaction either way (regardless of the moles of gas on each side of the chemical reaction)

melodyzaki2E

I think K would decrease since in an endothermic reaction is like having heat as a reactant but it will push the reaction forward so i'm not totally sure.

melodyzaki2E

and then if you're given pH and you need to find the H30+ concentration you just do the antilog: 10^(-pH)

melodyzaki2E

If you focus on the inverse relationship pressure has with volume, that tends to help.
It will go to the side with fewer moles when volume decreases or pressure increases, and vice versa.

melodyzaki2E

I think thats supposed to be a representation of the units, bars, thats used when solving the equilibrium constant using pressure. I'm not sure though.

melodyzaki2E

A 25.0-g sample of ammonium carbamate, NH4(NH2CO2), was placed in an evacuated 0.250-L fl ask and kept at 25 C. At equilibrium, 17.4 mg of CO2 was present. What is the value of Kc for the decomposition of ammonium carbamate into ammonia and carbon dioxide? The reaction is NH4(NH2CO2)(s)-->2 NH3(g) ...

melodyzaki2E

Consider the reaction 2 NO(g) --> N2(g) O2(g). If the initial partial pressure of NO(g) is 1.0 bar, and x is the equilibrium concentration of N2(g), what is the correct equilibrium relation?
How do you find the equilibrium constant formula?

melodyzaki2E

How do we find the equilibrium constants for weak acids/bases? Is it different from strong acids/bases?

melodyzaki2E

Does anyone have any advice on how to memorize all the different ligands?

melodyzaki2E

Use the information in Table 17.4 to write the formula for each of the following coordination compounds: (a) potassium hexacyanidochromate(III) (b) pentaamminesulfatocobalt(III) chloride (c) tetraamminediaquacobalt(III) bromide (d) sodium bisoxalato(diaqua)ferrate(III) Does anyone have the answers f...

melodyzaki2E

it has one sigma and two pi bonds but it has the same electron density as a single or triple bond, I think.

melodyzaki2E

A coordination number is the number of atoms or ions immediately surrounding a central atom in a complex.

melodyzaki2E

Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center: (a) HN(CH2CH2NH2)2; (b) CO3 2; (c) H2O;(d) oxalate.
What does 'polydentate' mean?

melodyzaki2E

polarity shouldn't affect the resonance structure, focus on the formal charge when determining resonance.

melodyzaki2E

a single bond is representative of one sigma bond; a double bond is representative of a sigma bond and a pi bond; a triple bond is representative of one sigma and two pi bonds.

melodyzaki2E

if the molecule is asymmetric, the bond dipole moments won't "cancel out" and the molecule will have a net dipole moment and the molecule is therefore polar, but if the molecule is symmetric, dipole moments will usually cancel out. hope this helps.

melodyzaki2E

There are images online that are seriously helpful in identifying the different shapes, I use them all the time to make sure I'm doing it right.

melodyzaki2E

How does polarity affect the molecular shape of molecules? Does it change their VSEPR model at all?

melodyzaki2E

When we draw molecules with more than one lone pair around the central atom, how do we depict that that is a trigonal planar or a tetrahedral since its not as obvious as those with atoms attached?

melodyzaki2E

I don't think it matters whether you make it positive or negative as long as you don't use the same four quantum numbers for two different elements.

melodyzaki2E

the speed of light formula is only used on wavelengths in the electromagnetic radiation spectrum, you can't use it when particle has mass (you have to use de broglie for that).

melodyzaki2E

I think one will always be at least slightly more electronegative than the other; if they're the same element (like N2) then there wouldn't be any dipole moments because they would have equal electronegativity, i'm not totally sure though.

melodyzaki2E

do you have any other examples that might make it a bit more clear? thanks so much.

melodyzaki2E

Review his notes a couple times because he talks about everything during class, and then I do practice problems from the book because it exposes you to different ways he might ask a question on the exam. Good luck!

melodyzaki2E

I think so. I don't think it matters too much as long as you don't assign the same four quantum numbers to any two elements.

melodyzaki2E

Which M2 ions (where M is a metal) are predicted to have the following ground-state electron configurations: (a) [Ar]3d7; (b) [Ar]3d6; (c) [Kr]4d4; (d) [Kr]4d3? Where do you start when you approach this problem?

melodyzaki2E

I think it has something to do with the particle in the box analogy, like the electron has to be found somewhere inside this diameter which is the box. I'm not sure though.

melodyzaki2E

The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? To what region of the electromagnetic spectrum does this wavelength correspond (i.e. infrared, ultraviolet, x-ray, etc.)? W...

melodyzaki2E

In 1.0 s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0 s?

Can someone please explain how to solve this question please? thanks.

melodyzaki2E

I think he also talked about how it was a theoretical concept used to explain other things? I'm a little unclear about that part.

melodyzaki2E

do you have to know how to get from l to n to figure that out or is it just something you have to know?

melodyzaki2E

The unit joules is equal to kg*m^2*s^-2 but I'm not totally sure how that would work in a conversion.

melodyzaki2E

I think he was just trying to get the fact that the length of the wavelength is inversely related to the frequency of the photons, so long wavelengths didn't have enough energy to allow electrons to escape the metal but short wavelengths had high frequency so they were able to excite the electrons i...

melodyzaki2E

In that question they tell you that the diagram shown is the molecular structure, so I think you could just count out each of the atoms and that would give you the molecular formula. That one confused me too.

melodyzaki2E

I think it can have more than one limiting reactant but the mole ratio has to be the same between them and the quantities used have to have to match that mole ratio, so that both are used up simultaneously. But i'm pretty sure that this is a very hypothetical situation and is not seen in chemical re...

melodyzaki2E

I believe that it is a seperate chemical equation that is happening using the same reactants, so they would probably make that distinction in the question. I think what they were trying to get across with the concept of "competing reactions" though is just that the actual yield might be le...

melodyzaki2E

If you start off with one molecule of water, you have to divide by Avogadro's number to convert the molecule to moles, and then you can multiply the mole by the molar mass of water to get grams. So you should end up with 2.991 x 10^-23 g/molecule. Does that make sense?

Search found 61 matches