Answer: 100.
Explanation:
1) The subscripts to the right of each element (symbol) in the chemical formula tells the number of atoms of that element present in one unit formula.
2) The unit formula of C₄H₄S₂ is equal to 1 molecule.
3) Therefore, there are 4 carbon atoms, 4 hydrogen atoms and 2 sulfur atoms in each molecule of C₄H₄S₂.
4) Then, you just have to multiply the corresponding subscript of the element times the number of molecules (25 in this case) to find the number of atoms of that kind.
5) These are the calculations for each element in the molecule C₄H₄S₂.
i) C: 4 × 25 = 100
ii) H: 4 × 25 = 100
iii) S: 2 × 25 = 50.
6) The question is about H only, so the answer is that there are 100 hydrogen atoms in 25 molecules of C₄H₄S₂.
