During the formation of HCI from `H_2` and `Cl_2`, two moles of hydrogen and three moles of `Cl_2` have been used. What is the limiting reagent ?

Answer

To determine the limiting reagent in the reaction between hydrogen (H₂) and chlorine (Cl₂) to form hydrogen chloride (HCl), we can follow these steps:

### Step 1: Write the balanced chemical equation.
The balanced chemical equation for the formation of HCl from H₂ and Cl₂ is:
\[ \text{H}_2 + \text{Cl}_2 \rightarrow 2 \text{HCl} \]

### Step 2: Identify the stoichiometric ratios.
From the balanced equation, we can see that:
- 1 mole of H₂ reacts with 1 mole of Cl₂ to produce 2 moles of HCl.

### Step 3: Determine the number of moles of each reactant.
According to the question:
- Moles of H₂ used = 2 moles
- Moles of Cl₂ used = 3 moles

### Step 4: Calculate the required moles of each reactant.
For the 2 moles of H₂ used, the amount of Cl₂ required can be calculated using the stoichiometric ratio:
- Since 1 mole of H₂ requires 1 mole of Cl₂, 2 moles of H₂ will require 2 moles of Cl₂.

### Step 5: Compare the available moles with the required moles.
- We have 2 moles of Cl₂ available, but we have 3 moles of Cl₂ in total.
- Since we only need 2 moles of Cl₂ to react with the 2 moles of H₂, we have excess Cl₂.

### Step 6: Identify the limiting reagent.
- H₂ is the limiting reagent because we have only 2 moles of it, which is less than the 2 moles of Cl₂ required for the reaction. The Cl₂ is in excess.

### Conclusion:
The limiting reagent in this reaction is **H₂**.

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