Given: SnO2 + 2H2 → Sn + 2H2O Tin oxide reacts with hydrogen to produce tin and water. How many moles of SnO2 are needed to produce 500.0 grams of Sn?

Answer: 4.2123 mol

First, calculate the no. of moles of Sn produced in the reaction. You can find this by dividing the mass of Sn produced by the atomic mass of Sn. You can find the atomic mass of Sn from the periodic table, usually it is the number at the bottom.

No. of moles of Sn produced = 500 / 118.7 = 4.2123 mol

From the equation, we can see that the mole ratio (the numbers in front of each substance) of SnO2 : Sn is 1:1, which means, 1 mole of SnO2 reacts to give out 1 mole of Sn, so, we can conclude that the no. of moles of SnO2 and Sn are the same.

Note that the no. of moles of SnO2 will be different if the mole ratio is not 1:1, for example, if the mole ratio are 1:2, which means 1 mole of SnO2 will give out 2 moles of Sn, so the no. of moles of SnO2 will be the no. of moles of Sn divided by 2.

But since the ratio for this reaction is 1:1, the no. of moles of SnO2 required will be 4.2123 mol as well.