How Do You Calculate the Change in Internal Energy for Hydrogen Gas?

AI Thread Summary
To calculate the change in internal energy for one mole of hydrogen gas heated from 278 K to 390 K at constant pressure, the formula used is ΔU = (1.5)nRT, where n is the number of moles, R is the universal gas constant, and T is the change in temperature. The calculation performed yielded a result of approximately 1396.84 J. However, the student is unsure why this answer is marked incorrect, suspecting it may relate to significant figures, despite being instructed to maintain five decimal places. The discussion highlights confusion over the application of significant figures and the correct interpretation of the formula. The student seeks clarification on the calculation process and potential errors.
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Homework Statement


One mole of hydrogen gas is heated from 278 K to 390 K at constant pressure. Hydrogen has a specific heat of 43.6 J/mol*K. The universal gas constant is 8.31451 J/K mol. Calculate the change in the internal energy of the gas. Answer in units of J


Homework Equations



Change in Internal energy = (1.5)nRT
n= number of moles
R= universal gas constant
T= change in temperature

The Attempt at a Solution


(1.5)(1 mol)(8.31451 J/k mol)(112 K)
=
1396.83768

what am i doing wrong??
the website i have to submit my homework to says it's incorrect...:eek:
 
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I think that's right... You may want to look at the significant figures though.
 
noo def not
my teacher HATES significant digits, so we're just supposed to carry it out about 5 decimal places
grr i can't figure this one out :(
 

Thread 'Errors and significant figures'

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...
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Thread 'A cylinder connected to a hanging mass'

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...
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