In the physical properties, it is mentioned that the element has 4 valence electrons. The elements in the periodic table are arranged such that, the number of valence electrons present in the neutral atoms belonging to a particular group is equal to the group number.
Thus, the unidentified element can be best classified as a nonmetal in period 4
Ans C)
Answer: The molar mass of water in the hydrate is 126.14.
Explanation:
4C₃H₅(NO₃)₃
------> 12CO₂
+ 6N₂
+ 10H₂O
+ O₂
mol of CO₂ = 
= 
mol ratio of CO₂ : C₃H₅(NO₃)₃
12 : 4
∴ if mole of CO₂ = 0.568 mol
then " " C₃H₅(NO₃)₃ = 
= 0.189 mol
∴ mass of nitroglycerin = mole * Mr
= 0.189 mol * 227.0995 g / mol
= 43.00 g