The formula mass of methane CH4 (C: 12.01 amu; H: 1.008 amu) is 16.04 amu 16.042 amu 52.08 amu 52.072 amu
The Correct Answer and Explanation is:
Correct Answer: 16.042 amu
To determine the formula mass of methane (CH₄), calculate the sum of the atomic masses of all atoms present in one molecule of the compound.
Methane consists of:
- One carbon (C) atom
- Four hydrogen (H) atoms
The atomic mass of carbon is 12.01 atomic mass units (amu), and the atomic mass of hydrogen is 1.008 amu.
The total mass contribution of the hydrogen atoms is:
4 hydrogen atoms × 1.008 amu = 4.032 amu
Now, add this to the mass of one carbon atom:
12.01 amu (carbon) + 4.032 amu (hydrogen) = 16.042 amu
Thus, the formula mass of CH₄ is 16.042 amu.
This value represents the mass of a single molecule of methane in atomic mass units, which is the standard unit used to express the masses of atoms and molecules. Methane is a simple hydrocarbon with a tetrahedral molecular geometry, composed of one carbon atom covalently bonded to four hydrogen atoms.
The importance of calculating the formula mass lies in its role in chemical calculations, including mole conversions, stoichiometry, and molecular analysis. A precise value, such as 16.042 amu instead of a rounded 16.04 amu, is essential in laboratory and theoretical chemistry for achieving accurate results, especially in reactions involving gaseous methane or those requiring high precision.
Incorrect options:
- 16.04 amu is a rounded approximation and lacks the precision of the correct value.
- 52.08 amu and 52.072 amu are too large and do not correspond to the composition of CH₄; such values suggest larger or different molecular structures.
Accurate calculation of formula mass ensures proper interpretation of chemical behavior and enables reliable quantitative analysis.
