Question

Chlorine gas can be produced commercially by passing an electric current through a concentrated solution of sodium chloride (brine). The equation is as follows: 2NaCl(aq) + 2H2O(l) → 2NaOH(aq) + Cl2(g) + H2(g). If the brine contains 250 g NaCl, how many moles of Cl2 can be produced?
A) 2.24 mol Cl2
B) 2.0 mol C2
C) 2.14 mol Cl2
D) 1.40 mol Cl2

Answer 1

We shall need the following equalities : 
moles = mass / Molar mass
1 mol NaCl = 58.4428 g NaCl 
1 mol Cl2 = 2 mol NaCl 

therefore
1 mol NaCl ---------------------------- > 58.4428 g NaCl 
X--------------------------------------------- > 250 g NaCl
x=250/58.4428=4.2776869 mol NaCl

1 mol Cl2 -----------------------> 2 mol NaCl 
  X------------------------------- > 4.2776869 mol NaCl
x=4.2776869/2=2.14 mol Cl2

the answer is 2.14 mol Cl2