# Problem: In a given diffusion apparatus, 15.0 mL of HBr gas diffuses in 1.0 min. In the same apparatus and under the same conditions, 20.3 mL of an unknown gas diffuses in 1.0 min. The unknown gas is a hydrocarbon.Find its molecular formula.

###### FREE Expert Solution
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###### FREE Expert Solution

Recall: Graham's Law of Effusion allows us to compare the rate of effusion of two gases. Graham's Law states that the rate of effusion of a gas is inversely proportional to its molar mass.

This means that when comparing two gases:

Let's designate HBr as gas 1 and the unknown as gas 2. We're given:
rateHBr = 15.0 mL/min                  MHBr = 1.01 g/mol H + 79.90 g/mol Br = 80.91 g/mol
rateunk = 20.3 mL/min                  Munk = ?

87% (227 ratings)
###### Problem Details

In a given diffusion apparatus, 15.0 mL of HBr gas diffuses in 1.0 min. In the same apparatus and under the same conditions, 20.3 mL of an unknown gas diffuses in 1.0 min. The unknown gas is a hydrocarbon.

Find its molecular formula.

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 Effusion concept. You can view video lessons to learn Effusion Or if you need more Effusion practice, you can also practice Effusion practice problems .

How long does this problem take to solve?

Our expert Chemistry tutor, Jules took 3 minutes to solve this problem. You can follow their steps in the video explanation above.

What professor is this problem relevant for?

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

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