All India Engineering / Architecture Entrance Examination (AIEEE)

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AIEEE 2007 Chemistry

Q. 1. The energies of activation for forward and reverse reactions for respectively. The presence of a catalyst lowers the activation energy of both (forward and reverse) reactions by 100 kJ mol^–1. The enthalpy change of the reaction in the presence of catalyst will be (in kJ mol^–1)

1. 300
2. 120
3. 280
4. 20

Sol: Enthalpy change of a reaction is not affected by the presence of a catalyst as it lowers the activation energy of the forward and reverse reaction by the same amount . None of the options given is correct but option (4) can be treated as correct in terms of magnitude. Correct choice: (4)

Q. 2. The cell, , was allowed to be completely discharged at 298 K. The relative concentration of ZnocellE

1. antilog (24.08)
2. 37.3
3. 
4. 

Sol:

Correct choice: (3)

Q. 3. The pK_a of a weak acid (HA) is 4.5. The pOH of an aqueous buffered solution of HA in which 50% of the acid is ionized is

1. 4.5
2. 2.5
3. 9.5
4. 7.0

Sol: If the given weak acid is 50% ionized, then its conjugate base will have the concentration same as that of weak acid.

Correct choice: (3)