Question

When salt-X is mixed with equal amount of K$_2$Cr$_2$O$_7$ in a test tube and conc. H$_2$SO$_4$ is added followed by heating the test tube, red fumes of compound-Y is obtained which is passed into NaOH solution. Solution becomes yellow due to formation of compound-Z. The sum of total atoms present in, Y and Z is

Answer 1

12

Answer 2

Solution:

1. Formation of Compound Y:
   When a chloride salt (salt‑X) is heated with K₂Cr₂O₇ and concentrated H₂SO₄, the chromyl chloride test is performed. The red fumes produced are of chromyl chloride,

   $$\text{CrO}_2\text{Cl}_2$$

2. Formation of Compound Z:
   Passing the red fumes into NaOH solution yields sodium chromate, which is yellow in color,

   $$\text{Na}_2\text{CrO}_4$$

3. Counting Total Atoms:

   • In $\text{CrO}_2\text{Cl}_2$:
     Cr:1, O:2, Cl:2 → Total = $1+2+2 = 5$ atoms
   • In $\text{Na}_2\text{CrO}_4$:
     Na:2, Cr:1, O:4 → Total = $2+1+4 = 7$ atoms

   So, the sum of the atoms is:

   $$5 + 7 = 12$$