Question

How many grams of solid product can be produced by mixing 45.6 grams of chlorine gas with excess sodium metal?

Answer 1

first, write the balanced equation:
Cl2 (g) + 2Na (s) --> 2NaCl (s)
*chlorine gas is diatomic*
then, do dimensional analysis to cancel units:
g of NaCl = (45.6 g Cl2)*(1 mol Cl2/35.45*2 g Cl2)*(2 mol NaCl/1 mol Cl2)*(58.45 g NaCl/1 mol NaCl)
*35.45 g is atomic mass of Cl, but since it is diatomic, it should be 35.45*2 g Cl2
*23 g is atomic weight of Na, thus 23 + 35.45 = 58.45 g is weight of NaCl

solving this, we obtain 75.2 g NaCl
(always check the number of significant digits)

so there,, :)