Tag: heat and thermodynamics

Quizzes (20) Questions (162)

Questions Related to heat and thermodynamics

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

The quantity of heat (in J) required to raise the temperature of $1.0\, kg$ of ethanol from $293.45\, K$ to the boiling point and then change the liquid to vapor at that temperature is closest to 
[Given : Boiling point of ethanol $351.45\, K$
              Specific heat capacity of liquid ethanol $2.44\, J\, g^{-1}\, K^{-1}$
               Latent heat of vaporization of ethanol $855\, J \, g^{-1}$]

  1. $1.42\, \times 10^2$

  2. $9.97\, \times 10^2$

  3. $1.42\, \times 10^5$

  4. $9.97\, \times 10^5$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Heat to raise temperature: Q1 = m * c * delta T = 1000g * 2.44 J/gK * (351.45 - 293.45)K = 1000 * 2.44 * 58 = 141,520 J. Heat to vaporize: Q2 = m * L = 1000g * 855 J/g = 855,000 J. Total Q = 141,520 + 855,000 = 996,520 J, which is approximately 9.97 * 10^5 J.

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

Which of the following statements are incorrect?
I. If $Q > 0$, heat is added to the system.
II. If $W > 0$, work is done by the system.
III. If $W = 0$, work is done by the system.

  1. II and III

  2. I, II and III

  3. I and II

  4. I and III
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

I is correct (heat added). II is correct (work done by system). III is incorrect because if W=0, no work is done by the system; the system is at constant volume.

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

A monatomic ideal gas expands at constant pressure, with heat Q supplied. The fraction of Q which goes as work done by gas is

  1. 1

  2. $\displaystyle{\dfrac{2}{3}}$

  3. $\displaystyle{\dfrac{3}{5}}$

  4. $\displaystyle{\dfrac{2}{5}}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$Q = nC _p \Delta T$ and $W = P\Delta V = nR\Delta T$
monatomic gas, $\displaystyle{C _p = \dfrac{5R}{2}}$.
$\Rightarrow$$\displaystyle{\dfrac{W}{Q} = \dfrac{2}{5}}$

Multiple choice principal and molar specific heats of gases isothermal and adiabatic processes specific heat capacity heat and thermodynamics physics

For a solid with a small expansion coefficient

  1. $ C _p - C _v = R $

  2. $ C _p = C _v $

  3. $ C _p $ is slightly greater than $ C _v $

  4. $ C _p $ is slightly less than $ C _v $
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For solids, the difference Cp - Cv is given by (alpha^2 * V * T * B) / beta, where alpha is the thermal expansion coefficient. Since alpha is small, Cp is slightly greater than Cv, but the difference is very small compared to gases.