Please don\'t answer unless you\'re sure! Which statement is *correct*? A The st
ID: 808209 • Letter: P
Question
Please don't answer unless you're sure!
Which statement is *correct*? A The standard entropy of a gas phase substance is less than the standard entropy of the same substance in the solid phase. For two different substances in the same phase, the substance with the more complex structure has the lower entropy. The more highly ordered allotrope of an element has a higher entropy. The entropies of elements and compounds are always positive. For a monatomic gas, the gas with the lower molar mass has the greater entropy.Explanation / Answer
1. Option A is incorrect.
Explanation: For a particular substance S(solid) > S(liquid) > S(gas) always.
2. Option B is incorrect.
Explanation: Consider the equation, S = k ln W. [W relates to the no of states and no of particles available, W = (number of states)number of particles]. For a complex molecule number of states is higher. So entropy is higher.
3. Option C in incorrect.
Explanation: Entropy is higher when the particles in the system is less ordered.
4. Option D is correct.
Explanation: Entropy of an element or a compound is always a positive quantity. Third law of thermodynamics presumes that a perfectly crystalline structure at '0'K has 'zero' standard entropy, but in reality this is not true because crystals always form at a finite temperature.
5. Option E in incorrect.
Explanation: Higher molar mass (or more perfectly higher number of electrons) indicates higher value of 'W' because of availability of more electronic states. So for monatomic gases, the gas with lower molar mass has the smaller entropy.