Hydrazine (n2h4), a rocket fuel , reacts with oxygen to form nitrogen gas and water vapor. the reaction is represented with the equation: n2h4(l) + o2(g) → n2(g) + 2h2o(g) how many grams of hydrazine are needed to produce 96.0g water?

The given equation is:
N2H4(l) + O2(g) → N2(g) + 2H2O(g)

From the periodic table:
mass of nitrogen = 14 grams
mass of hydrogen = 1 gram
mass of oxygen = 16 grams
Therefore:
molar mass of N2H4 = 2(14) + 4(1) = 32 grams
mass of water = 2(1) + 16 = 18 grams

From the balanced equation:
1 moles of N2H4 produces 2 moles of H2O.
32 grams of N2H4 produce 18*2=36 grams of water
To know the mass of N2H4 needed to produce 96 grams of water, all you need to do is cross multiplication as follows:
mass of N2H4 = (96*32) / 36 = 85.3334 grams

Exothermic,  physical change after it is already baked