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 step by step, we will analyze the reactions involved and the volumes of gases before and after the reactions.

### Step 1: Write the balanced chemical reaction
The reaction between carbon monoxide (CO) and oxygen (O2) can be represented as follows:
\[ 2 \text{CO} + \text{O}_2 \rightarrow 2 \text{CO}_2 \]

### Step 2: Determine the initial volumes of gases
From the question:
- Volume of CO = 20 ml
- Volume of O2 = 50 ml

### Step 3: Identify the limiting reagent
From the balanced equation, we see that:
- 2 volumes of CO react with 1 volume of O2.

Now, we need to find out how much CO is required to react with 50 ml of O2:
- For 50 ml of O2, the required volume of CO is:
\[ \text{Required CO} = 2 \times 50 \text{ ml} = 100 \text{ ml} \]

Since we only have 20 ml of CO, CO is the limiting reagent.

### Step 4: Calculate the volume of O2 that reacts with the available CO
Using the stoichiometry from the balanced equation:
- 2 ml of CO reacts with 1 ml of O2.
- Therefore, 20 ml of CO will react with:
\[ \text{O2 used} = \frac{20 \text{ ml CO}}{2} = 10 \text{ ml O2} \]

### Step 5: Calculate the volume of CO2 produced
According to the stoichiometry of the reaction:
- 2 ml of CO produces 2 ml of CO2.
- Therefore, 20 ml of CO will produce:
\[ \text{CO2 produced} = 20 \text{ ml CO2} \]

### Step 6: Calculate the remaining volume of O2 after the reaction
Initially, we had 50 ml of O2. After the reaction, the volume of O2 remaining is:
\[ \text{Remaining O2} = \text{Initial O2} - \text{O2 used} = 50 \text{ ml} - 10 \text{ ml} = 40 \text{ ml} \]

### Step 7: Identify the final gas mixture after shaking with KOH
When the resulting mixture is shaken with KOH, it will absorb the CO2 produced:
\[ \text{KOH} + \text{CO2} \rightarrow \text{K2CO3} + \text{H2O} \]
Since all the CO2 produced (20 ml) will react with KOH, it will be removed from the gas mixture.

### Final Result:
After the reaction and the absorption of CO2 by KOH, the gas left in the container is:
- Volume of O2 left = 40 ml

### Conclusion:
The final answer is:
**40 ml of O2 is left.**

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