Final answer:
The molecular formula of a compound with an empirical formula of CH₃ and a molecular mass of 30 amu is C₂H₆, as the empirical formula needs to be multiplied by 2 to reach the molecular mass.
Step-by-step explanation:
To determine the molecular formula of a compound with an empirical formula of CH₃ and a formula mass of 30 amu, we first need to calculate the mass of a single molecule of the empirical formula. The atomic mass of Carbon (C) is approximately 12 amu, and Hydrogen (H) is approximately 1 amu. Therefore, the empirical formula mass is (1 x 12 amu) + (3 x 1 amu) = 15 amu.
Next, we divide the molecular mass given in the question (30 amu) by the empirical formula mass just calculated (15 amu):
30 amu / 15 amu = 2.
This result tells us that the molecular formula contains twice as many atoms of each element as the empirical formula. So, to get the molecular formula we multiply each subscript in the empirical formula by 2: (CH₃)₂ = C₂H₆. Therefore, the molecular formula of the compound is C₂H₆.
The answer from the provided options is (d) C₂H₆.