Which has the maximum number of molecules among the following?

• 44 g CO₂

• 48 g O₃

• 8 g H₂

• 64 g SO₂

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 = 5 to n = 3 

C.

n= 6 to n = 5 

Energy of photon obtained from the transition n = 6 to n = 5 will have least energy.

Consider 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

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 15^o C  and the pressure 1.5 bar. If the bubbles rises to the surface where the temperature is 25^o 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 greater by a factor of 2.9

A.

Volume will become greater by a factor of 1.6 

i.e., volume of bubble will be almost 1.6 times to initial volume of bubble.