ZUMDAHL Marathon Problem: Chemistry Experts Only!!

sonar
Fri, 29 Oct 2004 16:09:55 +0000

Volume of cylinder @ max temp:

(pi * .00800 m^2 *.0598 m) = 1.20235 x 10^-5 L^3



Mass of the gaseous products:

22.7 g X - (.250 mol H2O)(18.0154 g H2O/1 mol H2O) = 18.19615 g gas



10000 g H2O * 9.52 C * 4.184 J/(C x g) = 398316.8 J = 398.3168 kJ

398.3168 kJ * (1 mol X / 1893 kJ) = .2104156 mol X

–

22.7 g X - (.300 mol CO2)(44.0098 g CO2 / 1 mol CO2) - ( .250 mol H2O) (18.0154 g H2O/1 mol H2O) - (.025 mol O2)(31.9988 g O2 / 1 mol O2) =

4.19324 g A



sum of enathalpy = formation of CO2 + H2O + O2 + A

398.3168 kJ = (.300 mol CO2)(-393.5 kJ / 1 mol CO2) + ( .250 mol H2O) (-286 H2O/1 mol H2O) + 0 + A

587.8668 kJ = A



The above is info I thought may be helpful

I think that that you need to find the pressure (use given and subtract out the water vapor?) Then use ideal gas law (PV = nRT) to get moles of gas.

I suppose that you could subtract out the volume of the traces amount of liquid water, then use ideal gas law.

From there, you have total moles of gas, subtract the knowns to get moles of A.

Divide the mass of A by the moles of A to get A’s molar mass.

I would hazard a guess that A is probably a familar molar mass.

Then empirical formula X, now that you have the composition and moles of all it’s products, then find the real formula.

That’d be my approach, but checking to see if it works will take too long :P

I’m probably wrong though XD

Anyway, my take on (a) lol