To determine the correct answer about the compound with the empirical formula [tex]\( CH_3 \)[/tex], let's analyze each statement.
Option A: It contains three times as many hydrogen atoms as carbon atoms.
- The empirical formula [tex]\( CH_3 \)[/tex] indicates that for every 1 carbon atom, there are 3 hydrogen atoms.
- Therefore, this statement is true because it explicitly states that the compound has three times as many hydrogen atoms as carbon atoms.
Option B: It consists of [tex]\( 75\% \)[/tex] hydrogen by mass.
- To determine the percentage by mass of hydrogen in [tex]\( CH_3 \)[/tex], we need to consider the atomic masses.
- The atomic mass of carbon (C) is 12, and that of hydrogen (H) is 1.
- The total mass of [tex]\( CH_3 \)[/tex] is [tex]\( 12 \)[/tex] (from 1 carbon) + [tex]\( 3 \times 1 \)[/tex] (from 3 hydrogens) = [tex]\( 15 \)[/tex].
- The mass of hydrogen in [tex]\( CH_3 \)[/tex] is [tex]\( 3 \)[/tex].
- The percentage by mass of hydrogen is therefore [tex]\( \left( \frac{3}{15} \right) \times 100 \% = 20\% \)[/tex].
- Hence, this statement is false because the compound does not consist of [tex]\( 75\% \)[/tex] hydrogen by mass.
Option C: Each molecule contains exactly four atoms.
- The empirical formula [tex]\( CH_3 \)[/tex] tells us that each molecule consists of 1 carbon atom and 3 hydrogen atoms.
- Adding these up, there are [tex]\( 1 + 3 = 4 \)[/tex] atoms in total per molecule.
- Therefore, this statement is true as each molecule contains exactly four atoms.
Option D: Each carbon atom is bonded to three hydrogen atoms.
- According to the empirical formula [tex]\( CH_3 \)[/tex], each carbon atom is indeed bonded to three hydrogen atoms.
- Thus, this statement is true.
After analyzing each option, it's clear that options A, C, and D are true. But if we must select the most accurate and least ambiguous statement, we consider the most definitive property from these options:
Option C: Each molecule contains exactly four atoms.
This is the most exact and comprehensive description based on the given empirical formula without requiring additional chemical bonding context.
Therefore, the correct answer is:
[tex]\[ \boxed{C} \][/tex]
