The molar mass of hf is 20.01 g/mol. how many moles of sn are required to react with 40 g of hf?

You are given the molar mass of HF equals 20.01 grams per mole and the mass of HF equals 40 grams. You are required to get the number of moles of Sn in the reaction. The balanced chemical reaction is Sn(s) + HF(g) -> SnF2(s) + H2(g). Note that one mole of Sn is required to react with one mole of HF. So use the given mass of HF to get the moles of Sn,  

40 g HF(1 mol HF/20.01 g HF)(1 mol Sn/1 mol HF) = 1.999 or 2 moles of Sn  

For cyclohexane compounds drawn in a chair conformation:   -axial bonds are vertical  -equatorial bonds are parallel to two bonds within the ring.  thus, as i assume the chair conformation is drawn:   -the x group is in an axial position, as are the five other vertical bonds.  -three axial bonds are on the top face of the ring  -the other three axial bonds are on the bottom face  the position of the second substituent on each ring carbon is equatorial.  gauche groups must be on an adjacent carbon such as carbon 6 and carbon 2, and also gauche groups are rotated by 60 degrees relative to each other.  drawing the newman projections for c1–c2 and c1–c6 aids in visualizing the groups that are gauche to the y group on c1.  click this link and watch some academic videos that may you more understand the topic 

Use a magnet to separate iron, evaporate water, i'm not sure how to separate the other two i'm sorry but good luck