1. How many moles of tin are needed to react with 3.5 moles of hydrogen fluoride?

1.75 mole of Sn

Explanation:

We'll begin by writing the balanced equation for the reaction. This is given below:

Sn + 2HF —> SnF2 +H2

From the balanced equation above,

1 mole of Sn reacted with 2 moles of HF.

Therefore, Xmol of Sn will react with 3.5 moles of HF i.e

Xmol of Sn = 3.5/2

Xmol of Sn = 1.75 mole

Therefore, 1.75 mole of Sn is needed to react with 3.5 moles of HF