Help with Entropy Homework: A+B to D, Heat & Exothermic?

  • Thread starter Thread starter quietrain
  • Start date Start date
  • Tags Tags
    Entropy
AI Thread Summary
The discussion focuses on calculating the entropy change and heat transfer for the reaction A + B → D at 300K. The user attempts to determine the entropy change using the equation change in s = ∫ Cp dT / T but is unsure about the temperature limits. They conclude that since the heat capacities equalize at a certain temperature, they can simplify the calculation. The resulting heat transfer calculation indicates that the reaction is exothermic, as heat is released. The conversation references MIT lecture notes to support the calculations and methodology.
quietrain
Messages
648
Reaction score
2

Homework Statement


if i have reaction A + B --> D

if i produce 1 mol of D, what is the entropy change?
how much heat is transferred?
is this exothermic or endothermic?

Homework Equations



reaction carried out at T = 300K,

molar heat capacities(constant Pressure),

CA = 5sqrt(T)
CB = 8sqrt(T)
CD = 12sqrt(T)

The Attempt at a Solution



change in s = ∫ dQ / T right?

so ∫ Cp dT /T

but what are my limits for my Temperature?

is it right to say since they equalize at some temperature, i don't need to know my upper bound?

so i take CD - (CB + CA) to get -1sqrt(T) ?

so Q = CpT = -1(sqrt300) * 300

so since it is -ve, heat is released, and reaction is exothermic?

thanks
 
Physics news on Phys.org


Are you sure this is all the data there is?
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top