4 g of helium is heated from − 2 0 ∘ C to 8 0 ∘ C. For helium c v = 0.75 and c p = 1.25 cal g − 1 C ∘− 1 (1 cal = 4.18 J). Which statements are correct?

Δ T = 100 K. Δ U = 4 × 0.75 × 100 = 300 cal = 1254 J (same at constant P and V ). At constant volume W = 0 . At constant pressure Q = 4 × 1.25 × 100 = 500 cal = 2090 J, so W = Q − Δ U = 836 J. Option D gives Δ U as the work and is wrong.

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Physics - Heat & Thermo Question with Solution | TestHub

PhysicsHeat & ThermoThermodynamics Laws & Specific Heats of GasesMedium2 minQB

PhysicsMediummultiple choice

4 g of helium is heated from $- 2 0^{\circ}$ C to $8 0^{\circ}$ C. For helium $c_{v} = 0.75$ and $c_{p} = 1.25$ cal $g^{- 1}$ $C^{\circ- 1}$ (1 cal = $4.18$ J). Which statements are correct?

Options:(select one or more)

Answer:

A, B, C

Solution:

$Δ T = 100$ K. $Δ U = 4 \times 0.75 \times 100 = 300$ cal = $1254$ J (same at constant $P$ and $V$ ). At constant volume $W = 0$ . At constant pressure $Q = 4 \times 1.25 \times 100 = 500$ cal = $2090$ J, so $W = Q - Δ U = 836$ J. Option D gives $Δ U$ as the work and is wrong.

Subject:PhysicsTopic:Heat & ThermoSubtopic:Thermodynamics Laws & Specific Heats of Gases

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