2Na + MgCl2 -> 2NaCl + Mg The problem is to find how many grams of sodium chloride is formed from 12.5g of sodium.

Answer 1

2Na + MgCl2 ==> 2NaCl + Mg .. single replacement

moles Na used = 12.5 g Na x 1 mole/22.99 g = 0.5437 moles Na

mass NaCl formed = 0.5437 moles Na x 2 moles NaCl/2 moles Na x 58.4 g/mole NaCl = 31.8 g (3 sig. figs.)