Answer: 1 mole
Explanation:
[tex]Sn+2HF\rightarrow SnF_2+H_2[/tex]
Moles of [tex]HF=\frac{\text{ given mass}}{\text{ molar mass}}[/tex]
Given mass= 40 g
Molar mass= 20.01 g/mol
Moles of [tex]HF=\frac{40g}{20.01g/mole}=2moles[/tex]
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.