Answer: 1 mole
Step-by-step explanation:

Moles of

Given mass= 40 g
Molar mass= 20.01 g/mol
Moles of
From the given balanced chemical equation, it can be seen that 2 moles of HF react with 1 mole of Sn.
Thus 1 mole of Sn are required to react with 40 g of HF.