Question

Solid iron(III) hydroxide decomposes to produce iron(III) oxide and water vapor. If 0.75 L of water vapor is produced at STP, how many grams of iron(III) oxide were produced?

Answer 1

the iron III oxide is irrelevant here, you need to use the volme of H2O produces as your starting point. Since the reaction occurs at STP, 1mol of water vapor will occupy 22.4L. Sicne you only made 0.75L, you only made 0.0335moles of H2O vapor. Now use the mole ratio from the balanced equation to find moles of iron III hydroxide you started with