Question

The chemical equation below shows the reaction between tin (Sn) and hydrogen fluoride (HF).

Sn + 2HF Right arrow. SnF2 + H2

The molar mass of HF is 20.01 g/mol. How many moles of Sn are required to react completely with 40 g of HF?
1 mole
2 moles
3 moles
4 moles

Answer 1

1 mole of Sn

Step-by-step explanation:

The balanced equation tells us that 2 moles of HF react with every 1 mole of Sn. That's a molar ratio of 1/2. We need half as many moles of Sn as we have of HF. Lets determine the moles of HF that are in 40 g of the material. The molar mass of HF is (1 + 19) = 20 grams/mole.

40 grams of HF means we have 2 moles of HF: (40g HF)/(20 grams/mole HF) = 2 moles HF. Since the molar ratio is 1/2, we only need 1 mole of Sn for this reaction.