alleryAn ideal gas expands isothermally into a vacuum. What is w?
- Positive
- Zero
- Negative
- Equal to q
Show answer and solution
Correct answer: B. Zero
The external pressure is zero in a vacuum, so no work is done and w = 0.
CBSE Class 11 (Science) Thermal Properties of Matter & Thermodynamics — practice questions — page 5
Explore 267 free Thermal Properties of Matter & Thermodynamics questions in CBSE Class 11 (Science) Physics. Open each question or exercise to read its content, reference answers and available explanation.
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An ideal gas expands isothermally into a vacuum. What is w?Read the answer and worked solution →For free isothermal expansion of an ideal gas, Joule found what about ΔU?Read the answer and worked solution →For an isothermal irreversible change, which relation holds between q and w?Read the answer and worked solution →Why is enthalpy H a state function?Read the answer and worked solution →At constant pressure, the heat absorbed by a system equals which quantity?Read the answer and worked solution →What is the sign of ΔH for an exothermic reaction?Read the answer and worked solution →In ΔH = ΔU + Δng RT, what does Δng stand for?Read the answer and worked solution →Water vaporises at 373 K with ΔH = 41.00 kJ/mol. What is ΔU, taking R = 8.3 J/mol K?Read the answer and worked solution →For which reaction is ΔH equal to ΔU?Read the answer and worked solution →What does a large heat capacity C mean for a given heat input?Read the answer and worked solution →What does specific heat measure?Read the answer and worked solution →How much heat raises 200 g of a metal (c = 0.5 J/g K) by 10 K?Read the answer and worked solution →For one mole of an ideal gas, what is Cp - CV?Read the answer and worked solution →Which instrument measures heat changes at constant volume?Read the answer and worked solution →Why is no work done in a bomb calorimeter, even with gases involved?Read the answer and worked solution →Heat measured in a calorimeter open to the atmosphere gives which quantity?Read the answer and worked solution →A bomb calorimeter (20.7 kJ/K) warms 1 K when 1 g of graphite burns. What is ΔU per mole?Read the answer and worked solution →How is the reaction enthalpy ΔrH calculated from molar enthalpies?Read the answer and worked solution →What is the sign of ΔH for melting any solid?Read the answer and worked solution →What is the standard enthalpy of fusion of ice in kJ/mol?Read the answer and worked solution →What is sublimation?Read the answer and worked solution →Which solid sublimes at 195 K?Read the answer and worked solution →What is bond dissociation enthalpy?Read the answer and worked solution →Why is a mean C-H bond enthalpy used for methane?Read the answer and worked solution →In gas-phase reactions, ΔrH approximately equals what?Read the answer and worked solution →Why is lattice enthalpy found by a Born-Haber cycle?Read the answer and worked solution →What is true of the sum of enthalpy changes around a Born-Haber cycle?Read the answer and worked solution →NaCl has lattice enthalpy +788 and hydration enthalpy -784 kJ/mol. What is ΔsolH?Read the answer and worked solution →What is enthalpy of dilution?Read the answer and worked solution →What does Hess's law state about enthalpy change?Read the answer and worked solution →
Worked practice questions
For free isothermal expansion of an ideal gas, Joule found what about ΔU?
- It equals w
- It is negative
- It is positive
- It is zero
Show answer and solution
Correct answer: D. It is zero
Joule measured q = 0 and w = 0 in free expansion, so ΔU = 0.
For an isothermal irreversible change, which relation holds between q and w?
- q = -w
- q = 2w
- q = w
- q = 0
Show answer and solution
Correct answer: A. q = -w
At constant temperature of an ideal gas ΔU = 0, so q + w = 0 and q = -w.
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