Question

Calculate the equivalent mass of potassium dichromate. The reduction half-reaction in acid medium is,
Cr₂O₇²⁻ + 14H⁺ + 6e⁻ → 2 Cr³⁺ + 7H₂O

Answer 1

Potassium dichromate in acidic medium is a strong oxidizer.

It means it gains electrons during redox reaction.

From the reaction above we have 6 electrons.

Molar mass for Potassium Dichromate is 294.18

Equivalent mass is :

294.18 / 6 = 49.03 g

Answer 2

Answer: Equivalent weight of $K_2Cr_2O_7$ in acidic medium is 49 g/eq.

Explanation: We are given an ionic equation of $K_2Cr_2O_7$, which is

$Cr_2O_7^{2-}+14H^++6e^-\rightarrow 2Cr^{3+}+7H_2O$

Molar mass of $K_2Cr_2O_7$ = (2 × 39) + (2 × 52) + (7 × 16)

Molar mass of $K_2Cr_2O_7$ = 294 g

Equivalent weight in a redox reaction is the molar mass divided by the number of electrons lost or gained in the reaction.

For, the above reaction:

Number of electrons lost = 6

Hence, the equivalent weight of $K_2Cr_2O_7$ is

$\text{Equivalent weight of }K_2Cr_2O_7=\frac{294}{6}$

Equivalent weight of $K_2Cr_2O_7$ = 49 g/eq