StemCET Logo

Chemistry Question 57 – NEET-UG 2024

← Back
In which of the following processes entropy increases? A. A liquid evaporates to vapour. B. Temperature of a crystalline solid lowered from 130 K to 0 K. C. 2NaHCO3(s)→Na2CO3(s)+CO2(g)+H2O(g) D. Cl2(g)→2Cl(g) Choose the correct answer from the options given below:

Entropy is a measure of the disorder or randomness of a system. An increase in disorder corresponds to an increase in entropy.

Step 1: Understand Entropy Changes in Different Processes✦ Active

Entropy (ΔS) is a measure of the disorder or randomness of a system. Generally, entropy increases when a system becomes more disordered. Key factors that increase entropy include phase transitions from solid to liquid to gas, an increase in the number of moles of gas, an increase in temperature, and an increase in the number of independent particles.

💡 Teacher's Secret Hint

Remember that entropy is a state function, and its change depends only on the initial and final states of the system.

Step 2: Evaluate Entropy Change for Each Given Process○ Expand

Let's analyze each process: A. A liquid evaporates to vapour: This is a phase transition from liquid to gas. Gases have significantly higher disorder than liquids, so entropy increases (ΔS>0). B. Temperature of a crystalline solid lowered from 130 K to 0 K: Lowering the temperature decreases the kinetic energy and vibrational motion of particles, leading to a more ordered state. Thus, entropy decreases (ΔS<0). At 0 K, a perfect crystalline solid has zero entropy. C. 2NaHCO3(s)→Na2CO3(s)+CO2(g)+H2O(g): In this reaction, 2 moles of solid reactants produce 1 mole of solid and 2 moles of gaseous products. The formation of gas from solid significantly increases the disorder of the system, so entropy increases (ΔS>0). D. Cl2(g)→2Cl(g): Here, 1 mole of gaseous diatomic molecules breaks into 2 moles of gaseous atoms. The number of gaseous particles increases, leading to greater disorder and thus an increase in entropy (ΔS>0).

💡 Teacher's Secret Hint

Pay close attention to the physical states (solid, liquid, gas) and the change in the number of moles of gas in chemical reactions.

Step 3: Identify the Correct Combination○ Expand

Based on the analysis, processes A, C, and D result in an increase in entropy. Therefore, the correct option is (2) A, C and D.

✦ STEM Console utilizes AI models to generate step-by-step explanations and math clues. AI can make mistakes.