Chapter 4 - Sections 4.1-4.9 - Exercises - Conceptual Problems - Page 192: 137

A

From the diagrams, you can see that there is 4 N2O4 and 6 N2H4. Using the chemical equation provided, you can see that 4 N2O4 should react with 8 N2H4, but you only have 6 (when multiplied by 4). So 3 N2O4 would react with 6 N2H4. Therefore, one N2O4 would be left, and answer a is the only one which has one molecule of N2O4.