We’re asked to **determine the molar mass** of an **unknown hydrocarbon** whose **density is measured to be 1.97 g/L at STP.**

Recall that we can use the **ideal gas equation** to find the *density* of a gas *(hydrocarbons usually exist as a gas at STP):*

$\overline{){\mathbf{P}}{\mathbf{V}}{\mathbf{=}}{\mathbf{n}}{\mathbf{R}}{\mathbf{T}}}$

$\frac{\mathbf{P}\overline{)\mathbf{V}}}{\overline{)\mathbf{V}}}\mathbf{=}\frac{\mathbf{nRT}}{\mathbf{V}}\phantom{\rule{0ex}{0ex}}\mathbf{P}\mathbf{=}\frac{{\mathbf{n}}\mathbf{RT}}{\mathbf{V}}$

What is the molar mass of an unknown hydrocarbon whose density is measured to be 1.97 g/L at STP?

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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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Based on our data, we think this problem is relevant for Professor McCrory's class at UMICH.