To determine which compound has the highest normal boiling point, we need to look at the molecular structure of the compounds. The compounds given are all alkanes, which are hydrocarbons with single bonds between carbon atoms. The general formula for alkanes is CnH2n+2, where n is the number of carbon atoms. Alkanes are non-polar molecules, and their boiling points generally increase with increasing molecular weight due to the greater Van der Waals forces (induced dipole-induced dipole interactions) between larger molecules.
Let's analyze each of the compounds:
A) C2H6 (Ethane) has 2 carbon atoms and 6 hydrogen atoms.
B) C3H8 (Propane) has 3 carbon atoms and 8 hydrogen atoms.
C) C4H10 (Butane) has 4 carbon atoms and 10 hydrogen atoms.
D) C5H12 (Pentane) has 5 carbon atoms and 12 hydrogen atoms.
The molecular weight of a molecule is calculated by summing the atomic weights of all the atoms in the molecule. Carbon has an atomic weight of approximately 12 atomic mass units (amu) and hydrogen has an atomic weight of about 1 amu.
Let's calculate the molecular weight for each compound:
A) For C2H6: (2 * 12 amu) + (6 * 1 amu) = 24 amu + 6 amu = 30 amu
B) For C3H8: (3 * 12 amu) + (8 * 1 amu) = 36 amu + 8 amu = 44 amu
C) For C4H10: (4 * 12 amu) + (10 * 1 amu) = 48 amu + 10 amu = 58 amu
D) For C5H12: (5 * 12 amu) + (12 * 1 amu) = 60 amu + 12 amu = 72 amu
Comparing the molecular weights of each compound:
Ethane (C2H6) = 30 amu
Propane (C3H8) = 44 amu
Butane (C4H10) = 58 amu
Pentane (C5H12) = 72 amu
The highest molecular weight is for pentane (C5H12), which is 72 amu, and since boiling point increases with molecular weight for alkanes, the compound with the highest normal boiling point among the given options is pentane.
Therefore, the correct answer is:
D) C5H12
