Question

How many grams of sodium chloride decompose to yield 15 grams of chlorine gas?

Answer 1

Answer:

24.6g of NaCl

Explanation:

Expression of the reaction:

            2NaCl →  2Na  +  Cl₂

Given parameters:

Mass of Cl₂  = 15g

Unknown:

Mass of NaCl  = ?

Solution:

To solve this problem, we have to use mole relationships.

 Find the number of moles of the mass of the given specie;

    Number of moles  = $\frac{mass}{molar mass}$  

     Molar mass of Cl₂  = 2(35.5) = 71g/mol

   Number of moles  = $\frac{15}{71}$   = 0.21mole

Now;

 From the balanced reaction equation;

        1 mole of Cl₂ is produced from 2 moles of NaCl;

      0.21 mole of Cl₂ will be produced from 0.21 x 2 = 0.42mole of NaCl

So,

  Mass of NaCl = number of moles x molar mass

    Molar mass of NaCl  = 23 + 35.5 = 58.5g/mol

 Mass of NaCl  = 0.42 x 58.5 = 24.6g of NaCl