Answer : The molecular weight of a substance is 157.3 g/mol
Explanation :
As we are given that 7 % by weight that means 7 grams of solute present in 100 grams of solution.
Mass of solute = 7 g
Mass of solution = 100 g
Mass of solvent = 100 - 7 = 93 g
Formula used :

where,
= change in freezing point
= temperature of pure water = 
= temperature of solution = 
= freezing point constant of water = 
m = molality
Now put all the given values in this formula, we get


Therefore, the molecular weight of a substance is 157.3 g/mol
Water can be turned to ice if to cold gas if to hot
ice can turn to water if to hot and stay the same if to cold
gas will turn to water if to hot and freeze to ice if to cold and the pattern keeps going like that.
hope this helps
One lone pair, as there is a single covalent bond between the hydrogen and the carbon, and a triple covalent bond between the nitrogen and the carbon, leaving two free electrons/one electron pair on the nitrogen..... I think ((: