Identify the gas laws from the following diagrams. (three diagrams, a, b and c, shown in the textbook with a '

Short Answer Questions · Q16

Q. Identify the gas laws from the following diagrams. (three diagrams, a, b and c, shown in the textbook with a 'Diagrams / Gas laws' answer table)

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Concept understanding — Gas Laws Overview

The gas laws are experimentally derived relationships connecting a gas's pressure ( $p$ ), volume ( $V$ ), temperature ( $T$ ), and amount ( $n$ ); the ideal gas equation is their unified summary.

Boyle's Law: $p \propto 1/V$ at constant $T, n$
Charles's Law: $V \propto T$ at constant $p, n$
Gay-Lussac's Law: $p \propto T$ at constant $V, n$
Avogadro's Law: $V \propto n$ at constant $p, T$
Combined, they give $\dfrac{p_1V_1}{T_1} = \dfrac{p_2V_2}{T_2}$ , useful when several of $p, V, T$ change together for a fixed amount of gas
Always use absolute (Kelvin) temperature

Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2019Set ANNUAL1 mark
$Q. Write the Van der Waals equation.$
›Reveal solutionSolution
The van der Waals equation, (P + an²/V²)(V − nb) = nRT, modifies the ideal gas law with two correction terms — one for intermolecular attractive forces (a) and one for the finite size of molecules (b).

Real gases deviate from ideal behaviour because (i) gas molecules do occupy a small but finite volume, and (ii) there are weak intermolecular attractive forces between them, both of which the ideal gas equation PV = nRT ignores. Van der Waals introduced two correction terms:

Pressure correction: an²/V² is added to the observed pressure P, because intermolecular attractions reduce the pressure a gas actually exerts.

Volume correction: nb is subtracted from the total volume V, because a fraction of the volume is occupied by the molecules themselves and isn't available for free movement.

Combining both corrections gives: (P + an²/V²)(V − nb) = nRT, where a and b are gas-specific van der Waals constants.

✓Final answer
$(P + an²/V²)(V - nb) = nRT.$
CBSE 2019Set ANNUAL1 markMCQ
$Q. Match the columns — Column A: (B) Charles' law. Choose the correct matching term from Column B.$
(i) Estimation of nitrogen
(ii) Estimation of halogen
(iii) V ∝ T
(iv) Concept of Ionisation
(v) Gain of electrons
›Reveal solutionSolution

Charles' law states that, at constant pressure, the volume of a fixed amount of gas is directly proportional to its absolute (Kelvin) temperature: V ∝ T.

Jacques Charles found experimentally that when the pressure and amount of a gas are held constant, its volume increases in direct proportion to its absolute temperature. This is expressed as V ∝ T, or V/T = constant. Of the five listed terms, this matches Charles' law correctly with the relation V ∝ T.

✓Final answer
$(iii) V \propto T.$

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Q.Identify the gas laws from the following diagrams. (three diagrams, a, b and c, shown in the textbook with a 'Diagrams / Gas laws' answer table)

Concept understanding — Gas Laws Overview

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