The electronegativity of nitrogen (N) is 3.0, while the electronegativity of hydrogen (H) is 2.1. As it can be seen that nitrogen (N) is more electronegative than that of hydrogen (H),
So electron pairs are attracted towards nitrogen and thus it carries a partial negative charge and hydrogen carries a partial positive charge. The image of electron distribution is attached as follows.
Thus NH₃ is a polar molecule .
The answer is b. 4.2 mole. The balanced reaction formula is 2LiOH + H2SO4 -->Li2SO4 + 2H2O. And the ratio of mole number of the reactants is the same as the ratio of coefficients.
The amount of energy released is calculated by the product of heat of fusion and mass.
The formula of amount energy released is given by:
(1)
Here,
q is amount of energy released
L is heat of fusion (
)
m is mass of water
Put all the given values in equation (1)

≅ 

Thus, amount of energy released is 