Mass analysis of a common drying agent of organic molecules reveals that it has the empirical formula P2O5. If the molar mass is 283.89 g/mol, which molecular formula is correct?

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### Determining the Molecular Formula from Empirical Formula and Molar Mass

Mass analysis of a common drying agent of organic molecules reveals that it has the empirical formula \( P_2O_5 \). If the molar mass is 283.89 g/mol, which molecular formula is correct?

- \(\quad\) \( P_2O_5 \)

- \(\quad\) \( P_4O_{10} \)

- \(\quad\) \( P_6H_{15} \)

- \(\quad\) \( P_5O_6 \)

- \(\quad\) \( P_3O_4 \)

#### Explanation

To determine the correct molecular formula, you divide the given molar mass by the molar mass of the empirical formula \( P_2O_5 \) and then use the resulting factor to scale the subscripts in the empirical formula. 

* **Step 1:** Calculate the molar mass of the empirical formula \( P_2O_5 \):

   - Phosphorus (P): \( 2 \times 30.97 \) g/mol
   - Oxygen (O): \( 5 \times 16.00 \) g/mol
   
   Molar mass of \( P_2O_5 \) = \( 2 \times 30.97 \) + \( 5 \times 16.00 \)
                           = \( 61.94 \) + \( 80.00 \)
                           = \( 141.94 \) g/mol

* **Step 2:** Divide the given molar mass by the molar mass of the empirical formula:
   
   Scaling factor = \( \frac{283.89\ g/mol}{141.94\ g/mol} \approx 2 \)

* **Step 3:** Multiply the subscripts in the empirical formula by this factor to get the molecular formula:

  Molecular formula = \( P_{2 \times 2}O_{5 \times 2} \)
                    = \( P_4O_{10} \)

Therefore, the correct molecular formula is **\( P_4O_{10} \)**.
Transcribed Image Text:### Determining the Molecular Formula from Empirical Formula and Molar Mass Mass analysis of a common drying agent of organic molecules reveals that it has the empirical formula \( P_2O_5 \). If the molar mass is 283.89 g/mol, which molecular formula is correct? - \(\quad\) \( P_2O_5 \) - \(\quad\) \( P_4O_{10} \) - \(\quad\) \( P_6H_{15} \) - \(\quad\) \( P_5O_6 \) - \(\quad\) \( P_3O_4 \) #### Explanation To determine the correct molecular formula, you divide the given molar mass by the molar mass of the empirical formula \( P_2O_5 \) and then use the resulting factor to scale the subscripts in the empirical formula. * **Step 1:** Calculate the molar mass of the empirical formula \( P_2O_5 \): - Phosphorus (P): \( 2 \times 30.97 \) g/mol - Oxygen (O): \( 5 \times 16.00 \) g/mol Molar mass of \( P_2O_5 \) = \( 2 \times 30.97 \) + \( 5 \times 16.00 \) = \( 61.94 \) + \( 80.00 \) = \( 141.94 \) g/mol * **Step 2:** Divide the given molar mass by the molar mass of the empirical formula: Scaling factor = \( \frac{283.89\ g/mol}{141.94\ g/mol} \approx 2 \) * **Step 3:** Multiply the subscripts in the empirical formula by this factor to get the molecular formula: Molecular formula = \( P_{2 \times 2}O_{5 \times 2} \) = \( P_4O_{10} \) Therefore, the correct molecular formula is **\( P_4O_{10} \)**.
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