Calculating molar specific heat capacity - not a monatomic gas

In summary, the conversation discusses calculating the molar specific heat capacity of an ideal gas when 25 J of heat is added while the gas expands at a constant pressure. The calculated value is -0.0918 J/(mole*Celsius) and there is a question about whether this can have a negative value. However, it is clarified that J/mole*C is the same as J/mole*Kelvin and no conversion is needed.
  • #1
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1. Suppose that 25 J of heat is added to one mole of an ideal gas. The gas expands at a constant pressure of 2.62 x 10^4 pascals while changing its volume rom 4.97 x 10^-4 m^3 to 7.02 x 10^-4 m^3. Calculate C_p and express in Joule / (mole * Celsius)

2. Relevant equations
Q = C_p*n*(delta T)
P(Delta V) = nR(Delta T)

3. Attempt at solution
25 J = C_p (1 mole) (Delta T)

Delta T = .64632 Kelvin
Delta T = -272.35 Celsius

25 J = C_p (1 mole) ( .272.35 Celsius)

C_p = -.0918 J / (mole*Celsius)

4. Question:
I inputted the answer into the online system as +.0918 J / (mole*celsius)
However, it is telling me that I am wrong.

Could there be a negative molar specific heat capacity? That doesn't make too much sense to me because shouldn't the molar specific heat raise the temperature?

Or did I do some stupid mistake with units/wrong equations?
 
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  • #2
Never mind.

I see that J/mole*C is the same thing as J/mole*Kelvin
No need for a conversion.
 

FAQ: Calculating molar specific heat capacity - not a monatomic gas

1. How is molar specific heat capacity different for a non-monatomic gas compared to a monatomic gas?

The molar specific heat capacity for a non-monatomic gas is higher than that of a monatomic gas because non-monatomic gases have more degrees of freedom, meaning they can store more thermal energy.

2. What is the formula for calculating molar specific heat capacity for a non-monatomic gas?

The formula for calculating molar specific heat capacity for a non-monatomic gas is C = (f/2)R, where C is the molar specific heat capacity, f is the degrees of freedom, and R is the gas constant.

3. How do you determine the number of degrees of freedom for a non-monatomic gas?

The number of degrees of freedom for a non-monatomic gas can be determined by using the formula f = 3N - k, where N is the number of atoms in the gas and k is the number of constraints on the gas.

4. Can molar specific heat capacity change with temperature for a non-monatomic gas?

Yes, molar specific heat capacity can change with temperature for a non-monatomic gas because as the temperature increases, the molecules have more kinetic energy and therefore more degrees of freedom, leading to a higher molar specific heat capacity.

5. How does the molar specific heat capacity of a non-monatomic gas compare to that of a solid or liquid?

The molar specific heat capacity of a non-monatomic gas is typically lower than that of a solid or liquid because gases have more degrees of freedom and can store more thermal energy per unit mass compared to solids and liquids.

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