Final answer:
The molecular formula of the hydrocarbon X that decolorizes bromine water and has a molar mass of 56 g/mol is most likely C4H8, which is characteristic of alkenes.
Step-by-step explanation:
To deduce the molecular formula of the hydrocarbon X that decolorizes bromine water but has no action on ammoniacal silver trioxonitrate (V) solution and has a molar mass of 56 g/mol, we make use of the given atomic masses of hydrogen (H=1) and carbon (C=12). Hydrocarbon X must be an alkene because alkenes react with bromine water, decolorizing it, and have no action on ammoniacal silver nitrate, which reacts with alkynes and aldehydes. Given the molar mass, we can calculate the number of moles of carbon and hydrogen in 56 g/mol.
If X were C2H6, its molar mass would be (2 × 12) + (6 × 1) = 30 g/mol, which is too low. C3H8 would have a molar mass of (3 × 12) + (8 × 1)= 44 g/mol, also too low. C4H10 has a molar mass of (4 × 12) + (10 × 1) = 58 g/mol, which is slightly higher than the given molar mass. However, if we consider the unsaturation due to the double bond in alkenes, C4H8 has a molar mass of (4 × 12) + (8 × 1) = 56 g/mol, which matches the given molar mass. Thus, the molecular formula of X is most likely C4H8.