For the formation of `NH_4HS`
`NH_3(g) +H_2S(g) hArr NH_4HS(s)`
The energy for formation is `DeltaH=-85 kcal`. Find the maxiumu rate constant of backward reaction at `27^@C` . The energy difference between reactant and threshold energy is `+105 kJ(K_b=5.4 xx 10^(-3) "mol litre"^(-1) sec ^(-1)`)

Explanation

To find the maximum rate constant of the backward reaction for the formation of `NH4HS`, we will use the Arrhenius equation and the given data. Here’s a step-by-step solution:

### Step 1: Understand the Reaction and Given Data
The reaction is:
\[ \text{NH}_3(g) + \text{H}_2\text{S}(g) \rightleftharpoons \text{NH}_4\text{HS}(s) \]

Given data:
- \(\Delta H = -85 \text{ kcal}\) (for the formation of `NH4HS`)
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