Numerical answer · +4 / −1
The number of hydrogen atoms in toluene (C₇H₈) is x.
Answer and solution
Answer 8
Solution
Chemistry ma’am · 3 steps
Read the subscript on H in the formula; for toluene, check it against the structure too.
- Read the formula. In a molecular formula, the subscript after each symbol is the number of atoms of that element in one molecule. In C₇H₈ the subscript on H is 8.
- Check the structure. Toluene is methylbenzene, C₆H₅-CH₃. The benzene ring keeps 5 hydrogens after one is replaced by the methyl group, and the methyl group carries 3.
5 + 3 = 8
- So. One molecule of toluene has 8 hydrogen atoms, so x = 8.
The common slip: 9. Counting the 6 hydrogens of plain benzene and forgetting that the methyl group replaces one of them gives 9, not 8.
The idea to keep. Subscripts in a molecular formula count atoms per molecule. Splitting the structure into its groups is a quick way to confirm the count.
Answer from the NTA final answer key. Solution by PrepWiser.