Which of the following feature of catalysts is described in reactions given below?
(i) `CO(g) +2H_(2)(g) overset(Cu//ZnO-Cr_(2)O_(3))rarr CH_(3)OH (g)`
(ii) `CO(g) +H_(2) (g) overset(Cu)rarr HCHO (g)`
(iii) `CO(g) +3H_(2)(g) overset(Ni)rarr CH_(4)(g) +H_(2)O(g)`

Options

A. Activity
B. Selectivity
C. Catalytic promoter
D. Catalytic poison

Answer

To analyze the reactions provided and determine the feature of catalysts described, we can follow these steps:

### Step 1: Identify the Reactions
We have three reactions involving carbon monoxide (CO) and hydrogen (H₂) as reactants, each leading to different products with different catalysts:
1. \( CO(g) + 2H_2(g) \overset{Cu/ZnO-Cr_2O_3}{\rightarrow} CH_3OH(g) \)
2. \( CO(g) + H_2(g) \overset{Cu}{\rightarrow} HCHO(g) \)
3. \( CO(g) + 3H_2(g) \overset{Ni}{\rightarrow} CH_4(g) + H_2O(g) \)

### Step 2: Analyze the Role of Catalysts
In each of these reactions, different catalysts (Cu/ZnO-Cr₂O₃, Cu, and Ni) are used to convert the same reactants (CO and H₂) into different products (methanol, formaldehyde, and methane respectively).

### Step 3: Determine the Feature of Catalysts
The key observation here is that the same reactants can yield different products depending on the catalyst used. This indicates that catalysts have a property known as **selectivity**. Selectivity refers to the ability of a catalyst to direct a reaction towards a specific product.

### Conclusion
The feature of catalysts described in the given reactions is **selectivity**. Different catalysts lead to different products from the same set of reactants.

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