1.    You have never done a chemical reaction with moles and mass before this, so this is a challenging problem to solve. I put this here as an option because while you have never done this specifically, you have done enough work with mass and moles to understand how each half of the equation is formed, and so can find the answers. The equation is perfectly balanced, so each mole of Tin (Sn) will produce one mole of H2. If you think you are the right track, you may email me for guidance and checks along the way.
Tin metal (Sn) reacts with hydrogen fluoride (HF) to produce tin (II) fluoride (SnF2) and hydrogen gas (H2) according to the following balanced equation.
Sn(s)+2HF(g)SnF2(s)+H2(g)
A.    How many moles of HF are required to react completely with 125.0g of Sn?

B.    How many grams of H2 would be formed by that amount of Sn and HF?

C.    How many moles of SnF2 would be formed by that amount of tin and HF?

D.    What do you think would happen if you added 10x more Sn and no extra HF to begin the reaction?