### problems

greenspun.com : LUSENET : UR General Chemistry : One Thread

could someone explain to me how to do the following problems: 17, 25, 27. I would really appreciate this very much.

-- Anonymous, February 02, 2000

Here is what I have for #17:

q = molar heat capacity x moles x Change in Temp (20.8 J/mol C) (39.1 mol) (38 C) = 30,900 Joules

W = -P X Change in Volume (-1 atm) (-122L) = -12,400 J

Delta E = q + W

-- Anonymous, February 02, 2000

#25

@ Constant Volume: q = (n)(C with subscript v)(Delta T) q = (33.3 mol)(44.6 J/C-mol)(50 C) = 74,000 Joules

Delta E = q + w: since Delta V=0 then w=0 and Delta E = q.

Delta H = Delta E + Delta P(V) = Delta E + nR(Delta T) Delta H = 74,300 J + (33.3 mol)(8.314)(50 K)= 88,100 J

@ Constant Pressure:

q = Delta H = (n)(specific heat capacity)(Delta T)= 88,100 J w = (-P)(Delta V) = (n)(R)(Delta T) = -13,800 J Delta E = q + w

Sorry about having to type out the word delta every time. I don't know how to use symbols in netscape.

-- Anonymous, February 02, 2000

Give #27 another try using the same concepts as you did for the last two. Look at what changes for each particular step and use those changes to find what it is asking for. If you want more on this question post another message. You have the ability now to do it I think.

-- Anonymous, February 02, 2000