Question

in the reaction 2Na + Cl2 --> 2NaCl how many grams of NaCl are produced when 25 g. of sodium reacts completely to form NaCl?

Answer 1

first thing to do here is to balance the chemical equation.
2Na + Cl2 --> 2NaCl
then we get the masses of Sodium and Chlorine from periodic table of elements in order to calculate the molar mass of NaCl. from periodic table,
Na = 23
Cl = 35.5
thus, NaCl = 23+35.5 = 58.5 g/mol
therefore,
25 g Na * (1 mol Na / 23 g Na) * (2 mol NaCl / 2 mol Na) * (58.5 g NaCl / 1 mol NaCl) = 63.57 g NaCl

note that the ratio (2 mol NaCl / 2 mol Na) came from the balanced chemical reaction.

hope this helps~ :)