CHEMISTRY COMMUNITY

Emma Randolph 1J

Why is the entropy of the surroundings equal to 0 for an irreversible equation?

Emma Randolph 1J

Why do units change for k depending on the order of the reaction?

Emma Randolph 1J

Can someone explain how to do 7.31 in the 7th edition? I'm confused as to how to rearrange the arrhenius equation.

Emma Randolph 1J

What are the units for k in the different orders of reaction?

Emma Randolph 1J

How are rate laws determined?

Emma Randolph 1J

What are the different units for k for 0 order 1st order and 2nd order reactions?

Emma Randolph 1J

Do we use half life for 0 order reactions or just 1st order?

Emma Randolph 1J

What is the difference between 0th order and 1st order reactions conceptually? I'm still confused as what the "order" is actually describing.

Emma Randolph 1J

Do we need to know delta G = -nFE for test 2?

Emma Randolph 1J

How are entropy and enthalpy related?

Emma Randolph 1J

For number 6k.5 in the 7th edition, it asks to write the balanced redox reaction for o3+Br--> o2 + BrO3- and I'm confused as to how to separate it into two different equations since there are two parts with Os.

Emma Randolph 1J

When asked what the initial and final oxidation numbers are is that just the charge of the ion?

Emma Randolph 1J

Why is the internal energy of an ideal gas in a reversible isothermal expansion equal to 0??

Emma Randolph 1J

When does delta H = q?

Emma Randolph 1J

Why is it that when a gas is at constant volume, the work is equal to zero and the internal energy is equal to the amount of heat supplied?

Emma Randolph 1J

For question 4C.3 when it asks to calculate the change in enthalpy when 765 J is transferred as heat to .820 mol Kr (g) at 298 K and 1.00 atm at constant pressure and constant volume, what equations would you use?

Emma Randolph 1J

When determining the internal energy accompanying a reaction, why does the second step involve using the equation q=-Ccal*(change in temp) ? I'm just confused as to why there's a negative sign.

Emma Randolph 1J

Does anyone understand what exactly "work" is? I'm confused as to what the difference is between work and energy. Are they the same?

Emma Randolph 1J

How do we know if a molecule is an acid or base if we are given a Ka, how do we know if the molecule is a base so we'd have to find the Kb?

Emma Randolph 1J

How are Ka and Kb related?

Emma Randolph 1J

When Ka is small, that means that the reaction favors the formation of products right? (and that there are more reactants?)

Emma Randolph 1J

For this question, it asks to rank the following solutions in order of increasing pH: (a) 1.0 * 10^-5 M HCl(aq); (b) 0.20 M CH3NH3Cl(aq); (c) 0.20 M CH3COOH(aq); (d) 0.20 M C6H5NH2(aq). Justify your ranking. How would I solve this ??

Emma Randolph 1J

For this question, it asks to calculate the h3O and OH concentrations, but I found that the H3O concentration is 2*10^-13 Does that mean that the solution is neutral? The question asking if it is, but is it??

Emma Randolph 1J

Because the reaction is responding to minimize the effect of increasing pressure, the more pressure you add to the products the more reactants will be made.

Emma Randolph 1J

If a reaction is endothermic and you added heat, would the Kw be bigger or smaller and why? I'm a bit confused.

Emma Randolph 1J

A sample of ammonium carbamate, NH4(NH2CO2), of mass 25.0 g was placed in an evacuated flask of volume 0.250 L and kept at 25 8C. 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(NH2CO...

Emma Randolph 1J

A reaction mixture is prepared by mixing 0.100 mol SO2, 0.200 mol NO2, 0.100 mol NO, and 0.150 mol SO3 in a reaction vessel of volume 5.00 L. The reaction SO2(g)+ NO2(g) -> NO(g) + SO3(g) is allowed to reach equilibrium at 460 C, when Kc = 85.0. What is the equilibrium concentration of each substanc...

Emma Randolph 1J

When solving for Q and comparing it to K, why is it that if Q < K it means that more products are formed and if Q > K it means more reactants are formed? I'm confused trying to figure this out conceptually.

Emma Randolph 1J

When calculating composite equations, why does the second reaction have to be squared? For example, in the book it gives the example 2P(g)+3Cl2(g)-> 2PCL3 PCl3(g) +Cl2 (g) -> PCl5 (g) and 2P(g)+ 5CL2 (g) -> 2PCl5(g) and states that K for the third reaction is equal to K1*K2^2. Why does the K value f...

Emma Randolph 1J

For the reaction N2(g) + 3H2(g) -> 2 NH3(g) at 400. K, K = 41. Find the value of K for each of the following reactions at the same temperature: (a) 2 NH3(g) -> N2(g)+3 H2(g) (b) 1/2 N2(g) + 3/2 H2(g) ->NH3(g) (c) 2 N2(g)+6 H2(g) -> 4 NH3(g). I understand that for part a you just put 1/41 to solve fo...

Emma Randolph 1J

Number 5G.9 asks: "A sample of ozone, O3, amounting to 0.10 mol, is placed in a sealed container of volume 1.0 L and the reaction 2 O3(g) S 3 O2(g) is allowed to reach equilibrium. Then 0.50 mol O3 is placed in a second container of volume 1.0 L at the same temperature and allowed to reach equi...

Emma Randolph 1J

For 5G.5, the question asks to calculate the value of K for the decomposition assuming that the initial pressure of X2 was at .10 bar. I'm just confused as to how you would go about calculating this?

Emma Randolph 1J

When coming up with the formula for a compund from its name, how do you know where to place the elements? For example, in exercise 3b in 9C of the 7th edition, the name of the compound is pentaamminesulfatocobalt (III) chloride. How do we know that means [Co(NH3)5(SO4)]Cl and not (NH3)5(SO4)CoCl ?

Emma Randolph 1J

Do we still have homework due this week?

Emma Randolph 1J

For Bronsted acids, is what makes the molecule an acid it separating in an aqueous solution?

Emma Randolph 1J

Can someone explain to me how to know if the hybridization of an atom is either in 1s or 2s? For example in number 2.45 in the 7th edition, the book asks to Identify the composition of the bonds and the hybridization of each lone pair—for example, by writing s (H1s,C2sp 2). How do you know that the ...

Emma Randolph 1J

Is test 3 just going to be on vsepr and hybridization?

Emma Randolph 1J

I'm still confused how to tell if a molecule is polar or nonpolar/ how to know which atom has the delta negative or delta positive charge. Is there a way you can tell which atom has the positive or negative charge by looking at the periodic table or something?

Emma Randolph 1J

Why is the shape of a molecule,such as XeF4 octahedral when there are 6 parts of electron density?

Emma Randolph 1J

Do we need to know how to figure out the hybridization of a central atom? and if so, how do we?

Emma Randolph 1J

How can you tell if a molecule is nonpolar or polar by just looking at the periodic table rather than looking up electronegativity?

Emma Randolph 1J

Do all tetrahedral molecules have a 109.5 degree angle in between the atoms?

Emma Randolph 1J

How do you know which compound has a greater ionic character or not? For example on the homework 2d.5, it's asking which has a greater ionic character HCl or HI but I'm not sure how to tell.

Emma Randolph 1J

Could someone please explain the differences between Lewis acids and bases? I know that the acids don't fill an octet and bases do or have a lone pair of electrons in the center, but what exactly does that mean? Thanks!

Emma Randolph 1J

Why is it that when an electron transitions from a higher to a lower energy level the energy of the photon emitted is negative?

Emma Randolph 1J

How do you know how many nodal planes exist for an orbital?

Emma Randolph 1J

For the photoelectric effect equation, is the kinetic energy always equal to 1/2mv^2 or can that be used for any part of the equation like the energy of the photon?

Emma Randolph 1J

Hi I'm just confused about why we have to find the formal charges of each atom/ what purpose it serves??

Emma Randolph 1J

I'm confused as to how to find/ if we have to know how to find the bond length of experimentally observed structures. For example, in lecture Professor Lavelle went over how Benzene has double and single bonds, with the double bonds being 1.34A and the single bonds being 1.54A, but the experimentall...

Emma Randolph 1J

yes I believe so

Emma Randolph 1J

I'm a bit confused as to why when we draw the Lewis Structure for the sulfate ion how it's okay for the sulfur to take in more than 8 electrons..Is there a limit of how many electrons it can take? How do we know how many electrons can fit into a atom?

Emma Randolph 1J

In lecture on Friday Professor Lavelle said that it doesn't matter :)

Emma Randolph 1J

For number 1E.7 on the homework, it asks to determine whether each of the following electron configurations represent the ground or excited state of an electron and I'm confused as to how you would determine that? please help

Emma Randolph 1J

For test 2, do we need to know how to find the quantum numbers of an electron? How do you do that?

Emma Randolph 1J

Will test 2 cover material about orbitals?

Emma Randolph 1J

For the photoelectric effect equation, do we need to use kg or g? In most examples I've only seen kg but could you also use grams for determing the energy?

Emma Randolph 1J

For homework problem 1B.15, they ask: The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 3 103 km?s 21. (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50...

Emma Randolph 1J

For question 1B.5, the book asks to calculate the wavelength of an atom with 140.511 keV of energy. I know how you would calculate this if the energy were in joules, but how do you convert this to joules?

Emma Randolph 1J

When trying to determine the wavelength and energy of photon for when the wave has a frequency of 300MHz, how would you do it? I'm confused how to apply the equations to the problem.

Emma Randolph 1J

Do we need to know how to calculate the percent yield for test 1?

Emma Randolph 1J

Are there any more practice problems that we could do to study for the test this week besides the ones in the homework? Also does anyone know what the format of the test is going to be?

Emma Randolph 1J

How many points will the test be out of?

Emma Randolph 1J

I'm still confused as to how the MinitialVinitial=mfinalvfinal formula applies to this problem, which values correspond to each part exactly?

Emma Randolph 1J

When balancing equations, I see that a lot of people say they start with the element that occurs the least. Does that mean the element with the least number of atoms on the reactant side, product side, or both? Or does it even really matter what order you balance an equation?

Emma Randolph 1J

Do we have to be aware of sig figs for every single calculation we carry out? I'm confused as to whether we don't have to worry about them or not when calculating something like molar mass.

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