20 ml of `CO` was mixed with 50 ml of `O_2` and the mixture was exploded. On cooling, the resulting mixture was shaken with KOH. Which gas and with what volume is left?

Options

A. `O_2`, 40 ml
B. `O_2`, 20 ml
C. `CO_2`, 10 ml
D. `CO_2`, 15 ml

Answer

To solve the problem, we will follow these steps:

### Step 1: Identify the reaction
When carbon monoxide (CO) reacts with oxygen (O₂), it produces carbon dioxide (CO₂) according to the following balanced chemical equation:
\[ 2 \text{CO} + \text{O}_2 \rightarrow 2 \text{CO}_2 \]

### Step 2: Determine the volumes of gases involved
We are given:
- Volume of CO = 20 ml
- Volume of O₂ = 50 ml

From the reaction stoichiometry, 2 volumes of CO react with 1 volume of O₂. Therefore, for 20 ml of CO:
- The amount of O₂ required = \( \frac{20 \text{ ml CO}}{2} = 10 \text{ ml O}_2 \)

### Step 3: Calculate the volume of CO₂ produced
According to the stoichiometry of the reaction, 20 ml of CO will produce 20 ml of CO₂.

### Step 4: Calculate the remaining volume of O₂
Initially, we had 50 ml of O₂. After the reaction, we used 10 ml of O₂:
- Remaining O₂ = Initial O₂ - Used O₂
- Remaining O₂ = 50 ml - 10 ml = 40 ml

### Step 5: Determine the gas left after shaking with KOH
When the resulting mixture is shaken with KOH, it absorbs CO₂. Since we produced 20 ml of CO₂, all of it will be absorbed by KOH. After the reaction and absorption:
- Remaining gases = Remaining O₂ = 40 ml

### Conclusion
After the reaction and the absorption of CO₂ by KOH, the gas left is oxygen (O₂) with a volume of 40 ml.

### Final Answer
The gas left is oxygen (O₂) with a volume of 40 ml.

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