Question

Hydrazine, N2H4, is used as a rocket fuel. In the reaction below, if 93.1 g of N2H4 and 105.7 g of N2O4 are allowed to react, how many grams of excess reactant remain at the end of the reaction?

2 N2H4 + N2O4 → 3 N2 + 4 H2O

Answer 1

Answer: 19.54 grams H2H4 remain

Step-by-step explanation:

The moles of each reagent are calculated by dividing the mass of each by its molar mass (g/mole).

N2H4: (93.1g/(32.0 g/mole) = 2.908 moles

N2O4: (105.7g/92.0 g/mole) = 1.149 moles

The balanced equation says we need one mole N2O4 per 2 moles N2H4. This means the 1.149 moles of N2O4 will consume 2*(1.149 moles) = 2.298 moles of N2H4. Since we start with 2.908 moles, (2.908 - 2.298) = 0.611 moles N2H4 will remain unreacted. Bummer. Multiply by the molar mass of N2H4 to obtain 19.55 grams unreacted N2H4.