Problem: An organic compound contains C, H, N, and O. Combustion of 0.1023 g of the compound in excess oxygen yielded 0.2766 g CO2 and 0.0991 g H2O. A sample of 0.4831 g of the compound was analyzed for nitrogen by the Dumas method (see Exercise 129). At STP, 27.6 mL of dry N2 was obtained. In a third experiment, the density of the compound as a gas was found to be 4.02 g/L at 127°C and 256 torr. What are the empirical and molecular formulas of the compound?

FREE Expert Solution

We’re being asked to determine the molecular formula of a terephthalic acid composed of C, H, and O given the combustion analysis.


Recall that in combustion analysisa compound reacts with excess O2 to form products


For a compound composed of C, H, and O, the reaction looks like this:


CxHyOz + O2 (excess)  x CO2y H2O


This means we need to do the following steps:

Step 1: Calculate the mass of C and H in the compound.

Step 2: Calculate the mass of O in the compound.

Step 3: Determine the lowest whole number ratio of C, H, and O to get the empirical formula.

Step 4: Use the empirical mass to calculate the molecular formula


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Problem Details

An organic compound contains C, H, N, and O. Combustion of 0.1023 g of the compound in excess oxygen yielded 0.2766 g CO2 and 0.0991 g H2O. A sample of 0.4831 g of the compound was analyzed for nitrogen by the Dumas method (see Exercise 129). At STP, 27.6 mL of dry N2 was obtained. In a third experiment, the density of the compound as a gas was found to be 4.02 g/L at 127°C and 256 torr. What are the empirical and molecular formulas of the compound?

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What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Standard Temperature and Pressure concept. You can view video lessons to learn Standard Temperature and Pressure. Or if you need more Standard Temperature and Pressure practice, you can also practice Standard Temperature and Pressure practice problems.

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Our data indicates that this problem or a close variation was asked in Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition. You can also practice Chemistry: An Atoms First Approach - Zumdahl Atoms 1st 2nd Edition practice problems.