9. Hydricarbon — Chemistry STD 11 Science — Question

${\text{2PQ}} \rightleftharpoons {{\text{P}}_2}{\text{  +  }}{{\text{Q}}_2}\,;\,\,\,\,{{\text{K}}_1}{\text{ =  2}}{\text{.5 }} \times \,{\text{1}}{{\text{0}}^5}\,$

${\text{PQ + }}\frac{1}{2}{R_2} \rightleftharpoons PQR\,;\,\,\,\,{{\text{K}}_2}{\text{ =  5 }} \times \,{\text{1}}{{\text{0}}^{ - 3}}\,$

The value of equilibrium constant for reaction

$\frac{1}{2}{{\text{P}}_2}{\text{ + }}\frac{1}{2}{{\text{Q}}_2}{\text{ + }}\frac{1}{2}{R_2} \rightleftharpoons PQR\,$ is

$Cr _2 O _7^{2-}+ XH ^{+}+6 Fe ^{2+} \rightarrow YCr ^{3+}+6 Fe ^{3+}+ ZH _2 O$

The sum of $X . Y$ and $Z$ is $.......$.