CHEMISTRY COMMUNITY

Ami_Pant_4G

I think for the nernst equation you could either use bar or atm, because they are almost the same. Also you can use both pressures and concentrations in the same equation, they don't all have to be the same. I don't know why that's the case but that's what my TA told me. Hope this helps.

Ami_Pant_4G

yes, p is for pressure, and the qp is delta H at constant pressure. Hope this helps.

Ami_Pant_4G

I think yes, if it doesn't say anything like "the starting or initial pH was...", you can assume it is at equilibrium.

Ami_Pant_4G

I thought the conjugate seesaw refers to the idea that the stronger the acid the weaker its conjugate base is and vice versa, I could be wrong though.

Ami_Pant_4G

When do we use the 3/2R or 5/2R in place of Cvm/Cpm? And when refering to mono, linear, or non-linear what exactly is that talking about. Thanks in advance.

Ami_Pant_4G

I think thermodynamic properties may be referring to things like entropy, ethalpy, and gibbs free energy, but I'm not entirely sure.

Ami_Pant_4G

Dinitrogen pentoxide, N2O5, decomposes by a first-order reaction. What is the initial rate of decomposition of N2O5 when 3.45 g of N2O5 is confined in a container of volume 0.750 L and heated to 65 C? For this reaction, k= 5.23x10^23 s^-1 in the rate law (for the rate of decomposition of N2O5). Can ...

Ami_Pant_4G

The “aluminum–air fuel cell” is used as a reserve battery in remote locations. In this cell, aluminum reacts with the oxygen in air in basic solution. (a) Write the oxidation and reduction halfreactions for this cell. (b) Calculate the standard cell potential For part A I figured out the half reacti...

Ami_Pant_4G

I'm a little confused on how to determine the two half reactions occurring in the cell. Can someone please explain how to determine them? thanks in advance.

Ami_Pant_4G

Predict the potential of each of the following cells:
(a) Pt(s)|H2(g, 1.0 bar)|HCl (aq, 0.075 mol/L)||HCl(aq, 1.0 mol/L) | H2(g, 1.0 bar)|Pt(s).

Can someone please explain why Cl is not included in the cell diagram? Thanks in advance.

Ami_Pant_4G

Can someone please explain why we would include the H+ in the cell diagram, but not include H20 in the diagram for part c? Thanks in advance.

Ami_Pant_4G

Can someone please explain how to find the pH? I am aware I will have to use the Nernst equation, but I don't understand how to progress. Thanks in advance.

Ami_Pant_4G

A student was given a standard Cu(s)uCu21(aq) half-cell and another half-cell containing an unknown metal M in 1.00 m M(NO3)2(aq) and formed the cell M(s)uM1(aq)uuCu21(aq)uCu(s). The cell potential was found to be 20.689 V. What is the value of E8(M21/M)? I keep getting an answer of 1.029 V but the ...

Ami_Pant_4G

(a) Write balanced half-reactions for the redox reaction of an acidified solution of potassium permanganate and iron(II) chloride. (b) Write the balanced equation for the cell reaction and devise a galvanic cell to study the reaction (write its cell diagram). How do we know that we don't need to inc...

Ami_Pant_4G

Can someone please explain how to write the half reactions of part b? thanks in advance.

Ami_Pant_4G

Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction.

Can someone please explain how to solve part b? Thanks in advance.

Ami_Pant_4G

Can someone please explain the statement max potential is reached when there is very little current flow? (this is from my notes, so I could have written is down wrong) Thanks in advance.

Ami_Pant_4G

Is a galvanic cell referring to the same thing as a battery system? thanks in advance.

Ami_Pant_4G

Will work always negative, because work should not be done on the system (which in this case is the battery system)? Thanks in advance.

Ami_Pant_4G

What would be some examples of work that the battery system does?

Ami_Pant_4G

I kind think of it as the word cathode has a "t" in it, which looks like a "+" sign so we know it gains electrons (which is what happens in reduction), and then anode is the opposite. Hope this helps.

Ami_Pant_4G

How do we know we should not make a separate half reaction for the oxygen and/or hydrogen in part b, but also in general? Thanks in advance.

Ami_Pant_4G

Because the anode is slowly losing mass, does that mean the cathode is slowly gaining mass? Thanks in advance.

Ami_Pant_4G

I think it is a similar to applying Le Chatelier's to change in temperature. When the cell potential is positive, it means the forward reaction is favored so when it is increased the forward reaction will occur. When the cell potential is negative, the reverse reaction is favored so when it is incre...

Ami_Pant_4G

(a) Calculate the work that must be done against the atmosphere for the expansion of the gaseous products in the combustion of 1.00 mol C6H6(l) at 25 8C and 1.00 bar. (b) Using data in Appendix 2A, calculate the standard enthalpy of the reaction. (c) Calculate the change in internal energy, DU8, of ...

Ami_Pant_4G

Calculate the final temperature and the change in enthalpy when 765 J of energy is transferred as heat to 0.820 mol Kr(g) at 298 K and 1.00 atm (a) at constant pressure; (b) at constant volume. Treat the gas as ideal. Can someone please explain how to find the final temperature for both parts? Also ...

Ami_Pant_4G

Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to the air in the pump? (c) What is the...

Ami_Pant_4G

Specific heat capacity is the heat required to increase the temperature of a substance by 1° per 1 gram of that substance. Dividing the heat capacity by grams of substance would give you the specific heat capacity. Hope this helps.

Ami_Pant_4G

I think you would calculate the entropy of the temperature change and volume change separately and then add the values together (since entropy is a state function) to calculate the total change in entropy. So for the change in volume you would use the deltaS = nRln(V2/V1) and for the change in tempe...

Ami_Pant_4G

When pressure increases, does entropy decrease? If so can someone please explain why? Thanks in advance.

Ami_Pant_4G

I think it means that it is very difficult to measure ∆G° in the lab, so the best way to determine it's value is through calculations with the gibbs energy equation. Hope this helps

Ami_Pant_4G

If the formula deltaS = nRln(V2/V1) is used for change in volume and isothermal, does that mean the pressure is constant as well?

Ami_Pant_4G

In calorimeter calculations, when is mass not taken into consideration?

Ami_Pant_4G

Can someone explain how degeneracy and the atom arrangements are relevant to entropy? thanks in advance.

Ami_Pant_4G

Can someone explain why we can say that the universe is an isolated system, when an isolated system means that no energy is transferred to the surrounding? Thanks in advance.

Ami_Pant_4G

When exactly would we need to use the work integral rather than the simplified version of -p(delta)v? Thanks in advance.

Ami_Pant_4G

Can someone please explain how a bomb calorimeter works? Like I understand that it is used for measuring specific heat/specific heat under a constant volume, but how exactly does it work? Thanks in advance.

Ami_Pant_4G

There were a couple of homework questions about calculating K of polyprotic acids so I would know how to do so. Hope this helps.

Ami_Pant_4G

A change in temperature would change K because the rate of the reaction would change if the temperature is increased or decreased. Hope this helps.

Ami_Pant_4G

I believe freezing and condensing are exothermic. Hope this helps.

Ami_Pant_4G

Method two uses bond enthalpies to calculate the change in heat of the reaction. You would use the enthalpies given from a table for the bonds within different molecule. Breaking bonds have positive enthalpies and forming bonds have negative enthalpies. You would add all the enthalpies of broken and...

Ami_Pant_4G

When a reaction is exothermic the heat can be considered to be a product, so if the temp increases then the reaction will shift toward the reactants and if the temp decreases then the reaction will shift toward the products. Hope this helps.

Ami_Pant_4G

Does the conjugate seesaw apply to the opposite statement or is it just one way? The weaker an acid/base is, the stronger it's conjugate base/acid is.

Ami_Pant_4G

Find the initial concentration of the weak acid or base in each of the following aqueous solutions: (a) a solution of HClO with pH 5 4.60; (b) a solution of hydrazine, NH2NH2, with pH 5 10.20.

Can someone please explain how to find part a? Thanks in advance.

Ami_Pant_4G

Calculate the pH of 0.010 M H2SeO4(aq), given that Ka1 is very large and Ka2 = 1.23 x10^-2. Can someone please explain how to do this, thanks in advance.

Ami_Pant_4G

When approximating for a small Ka, should we always calculate % ionization to ensure it is lower than 5%? Thanks in advance.

Ami_Pant_4G

When calculating the 5% ionization, if one of the reactants has a coefficient, of two for example, should the % ionization be 2x/initial x 100%? Thanks in advance

Ami_Pant_4G

Will we have to be able to calculate the ph of buffer solutions on the test?

Ami_Pant_4G

Adding water has no effect because liquids and solids do not influence equilibrium or the K value, only aqueous and gasses do. Hope this helps.

Ami_Pant_4G

The change in concentration is represented in terms of x and whether there is a coefficient paired with the x depends on if there are coefficients in the balanced equation. The negative signs depends on which way the reaction is occurring. Hope this helps.

Ami_Pant_4G

I believe it was K< 10^-3. Hope this helps.

Ami_Pant_4G

Knowing whether Q in relation to K would tell you at what point the reaction is at. For example, if Q is less than K you would know that it is at a pre-equilibrium state for the forward reaction because the concentration of reactants is higher than the concentration of products. And in terms of when...

Ami_Pant_4G

It can be any five problems, as long as they relate to whatever we have covered in class so far.

Ami_Pant_4G

If a reaction is multiplied, for example 2N2(g) + 6H2(g) <-> 4NH3(g) from N2(g) + 3H2(g) <-> 2NH3(g), why would the K value be raised to the second power? If the coefficients of the balanced equation can be reduced by some factor why would you need to raise K to some power? Thanks in advance.

Ami_Pant_4G

What are some instances that show light acts like a wave and not a particle?

Ami_Pant_4G

If a molecule has NH3 is it safe to assume it is a base?

Ami_Pant_4G

ASetlur_3I wrote:Just to clarify, polydentate ligands are chelating right?

yes all polydentates are chelating

Ami_Pant_4G

6C.19 Decide which acid in each of the following pairs is the stronger and explain why: (a) HF or HCl; (b) HClO or HClO2; (c) HBrO2 or HClO2; (d) HClO4 or H3PO4; (e) HNO3 or HNO2; (f) H2CO3 or H2GeO3.

Can someone please explain why HCl4 is stronger than H3PO4? thanks in advance

Ami_Pant_4G

Decide whether an aqueous solution of each of the following salts has a pH equal to, greater than, or less than 7. If pH . 7 or pH , 7, write a chemical equation to justify your answer. (a) NH4Br; (b) Na2CO3; (c) KF; (d) KBr; (e) AlCl3; (f) Cu(NO3)2 Can someone please explain why d is neutral and wh...

Ami_Pant_4G

Which is the stronger base, the hypobromite ion, BrO2, or morphine, C17H19O3N? Justify your answer.

How would determine which base is stronger? Thanks in advance.

Ami_Pant_4G

A careless laboratory technician wants to prepare 200.0 mL of a 0.025 m HCl(aq) solution but uses a volumetric flask of volume 250.0 mL by mistake. (a) What would the pH of the desired solution have been? (b) What will be the actual pH of the solution as prepared? Can someone please explain how to s...

Ami_Pant_4G

Write the chemical equations of the two proton transfer equilibria that demonstrate the amphiprotic character of (a) HCO3; (b) HPO42. Identify the conjugate acid–base pairs in each case.

Csn some one please explain how to do part b of this problem? Thanks in advance.

Ami_Pant_4G

What does mean for an anion to be stable?

Ami_Pant_4G

What does the Ka equilibrium constant represent and what is it used for? Thanks in advance.

Ami_Pant_4G

How do we know that the NH3 part of the coordination complex is supposed to be called ammine?

Ami_Pant_4G

Dr. Lavelle mentioned that the fifth bond on an iron atom to form a myoglobin protein is a histidine, but what exactly is a histidine?

Ami_Pant_4G

Besides representing the number of molecules/atoms bonded to the central metal atom, what is the use of the coordination number(if there is one)? Thanks in advance.

Ami_Pant_4G

Dipole-dipole bonds depend on the polarity of molecules where as dipole-induced dipole bonds (aka van der waals forces) depend of the polarizability of electron clouds. hope this helps:)

Ami_Pant_4G

Is the bond angle of bent 109.5 or 120? thanks in advance

Ami_Pant_4G

What is the purpose of hybridized orbitals? Thanks in advance.

Ami_Pant_4G

What does it mean for the vsepr model to be able to predict the distortion qualitatively but not quantitatively?

Ami_Pant_4G

Just to clarify, since bonds are treated the same in terms of regions of electron density in the vsepr model, it doesn’t matter what resonance structure is used right?

Ami_Pant_4G

What does the A in the AXE formula for molecular shape mean and can it ever have subscripts? Thanks in advance :)

Ami_Pant_4G

Can someone please explain why the lone-bonding pair repulsion is lower than the lone-lone pair repulsion? Thanks in advance

Ami_Pant_4G

What is the difference between a sigma bond and a pi bond? Also, what does it mean that a pi bond is unhybridized?

Ami_Pant_4G

Can someone please explain how we know when molecules have hybrid orbitals? Thanks in advance

Ami_Pant_4G

Can someone please explain why the interaction potential energy is always negative? Thanks in advance

Ami_Pant_4G

I think electronegativity is the major component to determining dipole moments. However, making the lewis structure can help you determine the molecular structure of a molecule which helps determine the polarity of the molecule as a whole. Hope this helps:)

Ami_Pant_4G

What is the difference between E=hv and E=pc? The notes made it seem that thy were both used to calculate energy of the photon, so would that mean the only difference is the circumstance in which you would use them?

Ami_Pant_4G

Can someone please explain why Sc+2 and potassium don't have the same valence shell electron configuration?

Ami_Pant_4G

Will we have to know how to calculate the charge difference/dipole moment for the midterm?

Ami_Pant_4G

What is the difference between polarizing power and polarizability? thanks in advance!

Ami_Pant_4G

In the lecture, Dr. Lavelle said that ions that cause large distortions have high polarizing powers, but what does large distortion mean? thanks in advance!

Ami_Pant_4G

Just for clarification, every covalent bond between two different atoms has a dipole moment, but not every covalently bonded molecule is necessarily polar, right?

Ami_Pant_4G

Can someone explain how a coordinate covalent bond is different from just a covalent bond? thanks in advance!

Ami_Pant_4G

The following Lewis structure was drawn for a Period 3 element. Identify the element.

To find the element you would have to count the number of electron are present in the lewis structure and match it up to the element in the third period of the periodic table, right? Thanks in advance.

Ami_Pant_4G

Just for clarification, the octet can be exceeded if atoms are in the d-block?

Ami_Pant_4G

Give the ground-state electron configuration and number of unpaired electrons expected for each of the following ions: (a) Sb 3 + ; (b) Sn 4 +; (c) W 2 +; (d) Br 2-; (e) Ni 2-

Can someone please explain how to find the number of unpaired electrons?

Ami_Pant_4G

On the basis of the expected charges on the monatomic ions, give the chemical formula of each of the following compounds: (a) magnesium arsenide; (b) indium(III) sulfide; (c) aluminum hydride; (d) hydrogen telluride; (e) bismuth(III) fluoride. Can someone please explain how to find a and b? Thanks i...

Ami_Pant_4G

When calculating formal charge, is each single bond counted as one or two shared electrons?

Ami_Pant_4G

What exactly does the "probability of electron density" mean in terms of the electron orbitals?

Ami_Pant_4G

f the following sets of four quantum numbers {n,l ,m l ,m s}, identify the ones that are forbidden for an electron in an atom and explain why they are invalid: (a) {4, 2, -1, +1/2}; (b) {5, 0, -1, +1/2}; (c) {4, 4, -1, +1/2}.

Can someone please explain why c) works

Ami_Pant_4G

Which of the following statements are true for many-electron atoms? If false, explain why. (a) The effective nuclear charge Z eff e is independent of the number of electrons present in an atom. (b) Electrons in an s-orbital are more effective than those in other orbitals at shielding other electrons...

Ami_Pant_4G

What is Hamiltonian and what is used for in terms of the Schrodinger equation?

Ami_Pant_4G

I understand that electrons in the same orbital have to have opposite spins, but what exactly does it mean for electrons to have opposite spins?

Ami_Pant_4G

For clarification, is this equation only used in terms of hydrogen atoms? If so, is there a more general equation that applies to other atoms?

Ami_Pant_4G

I am a bit confused about what the standing part of "circular standing wave" means? Can someone please clarify? Thanks in advance.

Ami_Pant_4G

Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589 nm. How much energy is emitted by (a) an excited sodium atom when it generates a photon; (b) 5.00 mg of sodium atoms emitting light at this wavelength; (c) 1.00 mol of sodium atoms emitting light at this wavelength? Fo...

Ami_Pant_4G

I think he was saying that De Broglie's equation can't be applied to light because the equation only applies to particles with really small masses and light has no mass. I could be wrong but that's how I interpreted it.

Ami_Pant_4G

In terms of the photoelectric model, it states that electrons will be ejected from the metal surface if the light frequency is high enough. But at what point is light frequency considered high enough to eject an electron?

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