Answer: The molecular mass of this compound is 131 g/mol
Explanation:
Depression in freezing point:
where,
= depression in freezing point =
= freezing point constant = 
m = molality
i = Van't Hoff factor = 1 (for non-electrolyte)
= mass of solute = 0.49 g
= mass of solvent (cyclohexane) = 20.00 g
= molar mass of solute = ?
Now put all the given values in the above formula, we get:
Therefore, the molar mass of solute is 131 g/mol
(1) The melting of a crystalline solid is best depicted by the second graph. This is because, the second graph shows a horizontal line which means that for a while there was no change in temperature. This zone is the latent heat of fusion.
(2) The first graph shows the graph of a solid that is just heated but does not experience phase change. However, the second graph shows a solid that changes phase (from crystal/solid to liquid).
Answer :
(a) The number of moles of D produced can be, 6.67 moles.
(b) The volume of D prepared can be, 24.5 L
Explanation :
The given chemical reaction is:

Part (a) :
From the balanced chemical reaction, we conclude that:
As, 3 moles of A react to give 5 moles of D
So, 4 moles of A react to give
moles of D
Thus, the number of moles of D produced can be, 6.67 moles.
Part (b) :
As we know that 1 moles of substance occupies 22.4 L volume of gas.
As,
volume of B gives
volume of D
As, 9.8 L volume of B gives
volume of D
Thus, the volume of D prepared can be, 24.5 L