Question:

X g of benzoic acid on reaction with aqueous \(NaHCO_3\) release \(CO_2\) that occupied 11.2 L volume at STP. X is ________ g.

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In such reactions, always use the stoichiometric relationship from the balanced chemical equation to convert volumes of gases into moles. Then use the molar mass to find the corresponding mass.
Updated On: Nov 1, 2025
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Approach Solution - 1

Step 1: Write the Balanced Chemical Equation

The reaction between benzoic acid (C\(_6\)H\(_5\)COOH) and sodium bicarbonate (NaHCO\(_3\)) is: \[ \text{C}_6\text{H}_5\text{COOH(aq)} + \text{NaHCO}_3\text{(aq)} \rightarrow \text{C}_6\text{H}_5\text{COONa(aq)} + \text{H}_2\text{O(l)} + \text{CO}_2\text{(g)} \]

Step 2: Calculate the Moles of CO\(_2\) Released

At STP (Standard Temperature and Pressure), 1 mole of any gas occupies 22.4 L. Given that 11.2 L of CO\(_2\) is released, the number of moles of CO\(_2\) is: \[ n_{\text{CO}_2} = \frac{11.2 \, \text{L}}{22.4 \, \text{L/mol}} = 0.5 \, \text{mol} \]

Step 3: Calculate the Moles of Benzoic Acid

From the balanced chemical equation, we can see that 1 mole of benzoic acid reacts to produce 1 mole of CO\(_2\). Therefore, the number of moles of benzoic acid is equal to the number of moles of CO\(_2\): \[ n_{\text{Benzoic Acid}} = n_{\text{CO}_2} = 0.5 \, \text{mol} \]

Step 4: Calculate the Mass of Benzoic Acid

The molar mass of benzoic acid (C\(_6\)H\(_5\)COOH) is: \[ \text{Molar Mass} = 6(12) + 5(1) + 12 + 2(16) + 1 = 72 + 5 + 12 + 32 + 1 = 122 \, \text{g/mol} \] The mass of benzoic acid is calculated as: \[ X = n_{\text{Benzoic Acid}} \times \text{Molar Mass} = 0.5 \, \text{mol} \times 122 \, \text{g/mol} = 61 \, \text{g} \]

Conclusion

The mass of benzoic acid is \( \boxed{61} \) grams.

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Approach Solution -2

Given: In the reaction of benzoic acid with aqueous sodium bicarbonate (\( \text{NaHCO}_3 \)), CO₂ is released. The volume of CO₂ produced is 11.2 L at STP. We know that at STP (Standard Temperature and Pressure), 1 mole of gas occupies 22.4 L. The balanced chemical equation for the reaction is: \[ \text{C}_6\text{H}_5\text{COOH (aq)} + \text{NaHCO}_3 \rightarrow \text{C}_6\text{H}_5\text{COONa (aq)} + \text{CO}_2 (g) + \text{H}_2\text{O (l)}. \]

Step 1: Moles of CO₂ Released

The volume of CO₂ released is given as 11.2 L. Using the molar volume of gas at STP (22.4 L = 1 mole), we can calculate the number of moles of CO₂: \[ \text{Moles of CO}_2 = \frac{11.2 \, \text{L}}{22.4 \, \text{L/mol}} = 0.5 \, \text{moles of CO}_2. \]

Step 2: Moles of Benzoic Acid Used

From the balanced equation, 1 mole of benzoic acid reacts with 1 mole of sodium bicarbonate to produce 1 mole of CO₂. Therefore, the moles of benzoic acid used will be the same as the moles of CO₂ produced: \[ \text{Moles of benzoic acid} = 0.5 \, \text{moles}. \]

Step 3: Mass of Benzoic Acid Used

The molar mass of benzoic acid (\( \text{C}_6\text{H}_5\text{COOH} \)) is 122 g/mol. Thus, the mass of benzoic acid used is: \[ \text{Mass of benzoic acid} = \text{moles} \times \text{molar mass} = 0.5 \, \text{moles} \times 122 \, \text{g/mol} = 61 \, \text{g}. \]

Final Answer:

The mass of benzoic acid used is \( \boxed{61} \, \text{g}. \)

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