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• ### Thermodynamics, piston-cylinder device?

5kg of air is contained in a piston-cylinder device, initially at a pressure of 2MPa and a specific volume of 0.08 m3/kg. The air the expands, as an ideal gas, through a polytropic process, with variable values of n, to a final specific volume of 0.30 m3/kg.

Determine the equations and steps you would take to determine the actual P, T, and v at all points along the process. Identify unknowns, equations, constants, and calculation orders.

• ### Ever wondered where to find information for felons / ex-offenders?

I'm curious to know if there are any other ex-offenders that have had the opportunity to visit the site http://www.felonsforum.com/ ? And I'm curious to know what they thought of the site, as well as what they would change about the site, if anything.

Keep in mind; felonsforum.com is dedicated to providing resources to ex-offenders. Please feel free to chime in, if you're an ex-offender and have some type of feed back to give regarding the forum.

H

2 AnswersOther - Politics & Government10 years ago
• ### Regarding a Hydrogen Atom?

Why is it, and I'm not asking for you to look this up, even though there is no true accepted answer; why is it that an electron from a hydrogen atom doesn't fall into the nucleus?

Meaning, what keeps the electron from falling into the nucleus of the atom?

I asked the Australian Yahoo!Answers this exact question. I'm curious now to see what fellow American nerds will say.

• ### Regarding a Hydrogen Atom?

Why is it, and I'm not asking for you to look this up, even though there is no true accepted answer; why is it that an electron from a hydrogen atom doesn't fall into the nucleus?

Meaning, what keeps the electron from falling into the nucleus of the atom?

• ### Born-Haber cycle determining electron affinity of Br?

Hello all! I'm studying for an exam. On my review sheet there is this problem:

Use the data given below to construct a Born-Haber cycle to determine the electron affinity of Br.

DH°(kJ)

K(s) → K(g) 89

K(g) → K⁺(g) + e⁻ 419

Br2(l) → 2 Br(g) 193

K(s) + 1/2 Br2(g) → KBr (s) -394

KBr(s) → K⁺(g) + Br⁻(g) 674

I'm completely stumped. I'm not sure that I completely understand Born-Haber cycle, so if you could please explain how you solve this problem, it'd be much appreciated.

• ### Can you identify the largest Marijuana plant?

Which is larger: the indica m.j. or the sativa? As many points to you for the right mj plant which grows the largest; and a thumbs up to you if you can tell me where the tallest mj plant is found!

Cheers!

D

• ### Calculate the wavelength of a baseball?

Okay, I don't know what I'm doing wrong here... I'm studying for a midterm. Here's the question on the review packet:

Calculate the wavelength of a baseball (m = 155 g) moving at 32.5 m/s.

I keep getting that the wavelength is 1.389*10^-34

The answer that I have to choose from are:

A) 1.32 × 10-34 m

B) 3.57 × 10-32 m

C) 2.15 × 10-32 m

D) 7.60 × 10-36 m

E) 2.68 × 10-34 m

So I'm inclined to say the answer's 'A', but why I can't get that exact value is beyond me. I thought it was a rounding issue, but I'm thinking there's something I'm doing wrong.

Thanks, once again Chemistry masterminds.

• ### Calculating energy evolved during a reaction?

Hello again everyone! I'm still working through this monsterous packet of review problems for my up and coming midterm. I'm stumped again. If you could help me establish the problem and how one would go about figure out this problem, it'd be greatly appreciated, as always.

According to the following reaction, how much energy is evolved during the reaction of 2.50 L B2H6 and 5.65 L Cl2 (Both gases are initially at STP)? The molar mass of B2H6 is 27.67 g/mol.

B2H6(g) + 6 Cl2(g) → 2 BCl3(g) + 6 HCl(g)

DH°rxn = -1396 kJ

A) 352 kJ B) 156 kJ C) 508 kJ D) 58.7 kJ E) 215 kJ

• ### Problems Calculating ΔH°f for a Review Exam?

My teacher has given us a Review Exam for my chemistry class. I'm completely lost as to what is going on here. I've pasted the exact question below. I think there's a typo because, as you'll see, she has SO3 -297, and this value is throwing me off. If you understand this problem and can make sense of it, could you please share. Also, if you're willing to guide me in solving this problem, I'd appreciate it; as again think there's a typo; that or I'm completely lost.

Use the DH°f and DH°rxn information provided to calculate DH°f for SO3(g):

DH°f (kJ/mol) 2 SO2(g) + O2(g) → 2 SO3(g)

DH∘

rxn = -198 kJ

SO2(g) -297

A) -578 kJ/mol

B) -792 kJ/mol

C) -495 kJ/mol

D) -396 kJ/mol

E) -248 kJ/mol

• ### Heat, Heat Capacity, and Work?

Hello all, I'm stuck on yet another practice problem from my chemistry class.

The air within a piston equipped with a cylinder absorbs 565 J of heat and expands from an initial volume of .10 L to a final volume of .85 L against an external pressure of 1.0 atm. What is the change in internal energy of the air within the piston?

If you could explain your steps I'd appreciate it. I keep ending up with 423J but the book says it should be 489J