Multiple Choice QuestionsConsider the following processes Δ H (kJ/mol)
1/2 A → +150
3B → 2 C + D -125
E + A → 2D +350
For B + D → E + 2C, ΔH will be
525 kJ/mol
-175 kJ/mol
-325 kJ /mol
-325 kJ /mol
B.
-175 kJ/mol
Match (I) with list (II) for the compositions of substances and select the correct answer using the code given below the lists.
|
|
List I (substance) |
|
List II Composition |
|
A. |
Plaster of Paris |
1. |
CaSO4.2H2O |
|
B. |
Epsomite |
2. |
CaSO4. ½ H2O |
|
C. |
Kieserite |
3. |
MgSO4. 7H2O |
|
D. |
Gypsum |
4. 5. |
MgSO4.H2O CaSO4 |
|
A |
B |
C |
D |
|
3 |
4 |
1 |
2 |
|
A |
B |
C |
D |
|
2 |
3 |
4 |
1 |
|
A |
B |
C |
D |
|
1 |
2 |
3 |
5 |
|
A |
B |
C |
D |
|
1 |
2 |
3 |
5 |
B.
|
A |
B |
C |
D |
|
2 |
3 |
4 |
1 |
Plaster of paris = CaSO4.1/2 H2O
Epsomite =MgSO4.7H2O
Gypsum = CaSO4.2H2O
Kieserite = MgSO4.H2O
According to the Bohr theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon?
n= 6 to n = 1
n = 5 to n = 4
n= 6 to n = 5
n= 6 to n = 5
C.
n= 6 to n = 5
Which has the maximum number of molecules among the following?
44 g CO2
48 g O3
8 g H2
8 g H2
A.
44 g CO2
44 g CO2 = 1 mol CO2 = NA molecules of CO2
48 g O3 = 1 mol O3 = NA molecules of O3
8 g H2 = 4 mol H2 = 4 x NA molecules of H2
64 g SO2 = 1 mol SO2 = NA molecules of SO2
The half -life of a substance in a certain enzyme catalysed reaction is 138 s. The time required for the concentration of the substance to fall from 1.28 mg L-1 is
414 s
552 s
690 s
690 s
C.
690 s
Enzyme -catalysed reactions follow first order kinectics.
therefore,
Fall of concentration from 1.28 mg L-1 to 0.04 mg L-1 involves five half - lives.
A 0.1 molal aqueous solution of a weak acid is 30% ionised. if Kf for water is 1.86oC/m, the freezing point of the solution will be
-18oC
-0.54oC
-0.36oC
-0.36oC
D.
-0.36oC
What is the value of electron gain enthalpy of Na+ if IE1 of Na = 5.1 eV?
-5.1 eV
-10.2 eV
+2.55 eV
+2.55 eV
A.
-5.1 eV
IE1 of Na = - Electron gain enthalpy of Na+ ion.
= -5.1 eV.
Which of the following structures is the most preferred and hence of lowest energy of SO3 ?
D.
Formal charges help in the selection of the lowest energy structure from a number of possible energy structure from a number of possible Lewis structures for a given species. Generally, the lowest energy structure is the one with the smallest formal charges on the atoms.
Formal charge on an atom: = total number of valence electrons- non - bonding electrons - 1/2 x bonding electrons.
For lewis structure of SO3
Formal charge on three O atoms
A bubble of air is underwater at temperature 15o C and the pressure 1.5 bar. If the bubbles rises to the surface where the temperature is 25o C and the pressure is 1.0 bar, what will happen to the volume of the bubble?
Volume will become greater by a factor of 1.6
Volume will become greater by a factor of 1.1
Volume will become smaller by a factor of 0.70
Volume will become smaller by a factor of 0.70
A.
Volume will become greater by a factor of 1.6
Which of the following statements in incorrect?
pure sodium metal dissolves in liquid ammonia to give blue solution
NaOH reacts with glass to give sodium silicate
Aluminium reacts with excess NaOH to give Al(OH)3
Aluminium reacts with excess NaOH to give Al(OH)3
C.
Aluminium reacts with excess NaOH to give Al(OH)3
Aluminium being amphoteric reacts with aqueous alkalies with the evolution of H2 gas.
2 Al (s) + 2NaOH (aq) + 6H2O (l) --> 2Na+[Al(OH)4]- (aq) +3 H2 ↑
