Heat needed to change temperature of hydrogen gas

AI Thread Summary
To calculate the heat needed to change the temperature of 0.650 moles of hydrogen gas from 50 K to 100 K, the equation Q=nC_v(T_f-T_i) is used. The user initially assumed hydrogen is diatomic, using C_v = 5/2 R, but struggled with the calculations. After recalculating with a different approach, the user still arrived at incorrect results. The discussion highlights confusion over using the correct molar mass and specific heat capacity for diatomic versus monatomic hydrogen. Clarification on these values is essential for accurate heat calculation.
Kalie
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A rigid container holds 0.650 of hydrogen gas. How much heat is needed to change the temperature of the gas from 50 K to 100 K?
All right I know this is easy but for some reason I can't get the right answer what i have been doing is using the equation Q=nC_v(T_f-T_i)
Hydrogen gas is 1 g/mol
so n= .65 mol
C_v= 5/2 R= 20.775
because hydrogen gas is diatomic?
(T_f-T_i)= 100-50= 50
so putting it all together I get 675.188
which is wrong I made Hydrogen monotomic for the hay of it and got 405 J which is wrong too.
Please tell me what I am doing wrong...:cry:
 
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Kalie said:
A rigid container holds 0.650 of hydrogen gas. How much heat is needed to change the temperature of the gas from 50 K to 100 K?
All right I know this is easy but for some reason I can't get the right answer what i have been doing is using the equation Q=nC_v(T_f-T_i)
Hydrogen gas is 1 g/mol
so n= .65 mol
C_v= 5/2 R= 20.775
because hydrogen gas is diatomic?
(T_f-T_i)= 100-50= 50
so putting it all together I get 675.188
which is wrong I made Hydrogen monotomic for the hay of it and got 405 J which is wrong too.
Please tell me what I am doing wrong...:cry:

See the highlights in the quote. A contradiction?
 
OlderDan said:
See the highlights in the quote. A contradiction?
But i also calculated it for monotomic too...
 
Kalie said:
But i also calculated it for monotomic too...

Did you calculate it for diatomic using the correct mass?
 
OlderDan said:
Did you calculate it for diatomic using the correct mass?
Oh!
But When I do that I get
.65/2 = .325
.325*20.775*50 = 337.6 which is still wrong
 
nevermind monatomic at that temp
 

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