All India Engineering / Architecture Entrance Examination (AIEEE)

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AIEEE 2007 Chemistry

Q. 23. Which of the following sets of quantum numbers represents the highest energy of an atom?

Sol: An orbital having higher value of (n + l) has higher energy. Out of the four options given, the value of (n + l) is highest if n = 3 and l = 2. Correct choice: (2)

Q. 24. Which of the following hydrogen bonds is the strongest?

1. O–H.…N
2. F–H.…F
3. O–H.…O
4. O–H.…F

Sol: Greater the difference in electronegativity of H–atom and the other electronegative atom with which H is covalently bonded, stronger is the hydrogen bond. Highest electronegativity difference exists in HF molecule. Correct choice: (2)

Q. 25. In the reaction,

1. 6 L HCl(aq) is consumed for every 3 L H₂(g) produced.
2. 33.6 L H₂(g) is produced regardless of temperature and pressure for every mole Al that reacts.
3. 67.2 L H₂(g) at STP is produced for every mole Al that reacts.
4. 11.2 L H₂(g) at STP is produced for every mole HCl(aq) consumed.

Sol: Given that,
For each mole of Al reacted, 1.5 mol of H₂ is formed; and for each mole of HCl(aq) consumed, 0.5 mol or 11.2 L of H₂ at STP is formed. Correct choice: (4)

Q. 26. Regular use of which of the following fertilizers increases the acidity of soil?

1. Potassium nitrate
2. Urea
3. Superphosphate of lime
4. Ammonium sulphate

Sol: Ammonium sulphate is a salt of weak base and strong acid. Its aqueous solution is acidic due to hydrolysis of ammonium ion. It will increase the acidity of soil. Correct choice: (4)

Q. 27. Identify the correct statement regarding a spontaneous process:

1. For a spontaneous process in an isolated system, the change in entropy is positive.
2. Endothermic processes are never spontaneous.
3. Exothermic processes are always spontaneous.
4. Lowering of energy in the reaction process is the only criterion for spontaneity.

Sol: For a process to be spontaneous in an isolated system, the change in entropy is positive. Correct choice: (1)

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