# Question #2e2b3

##### 2 Answers

The number of moles is

That's a Chemistry question and you need to use the ideal gas law to find the number of moles

Here, we have a ballon with a radius of

The volume is given by

The pression

Therefore, by the Rule of Three :

For the temperature,

For the mass,

The molar mass of

Therefore,

The number of moles of helium will be equal to **1.1** and the mass of helium will be **4.4 g**.

**SIDE NOTE** *Small correction - helium cannot exist as a diatomic molecule, so the correct notation is* *not*

There's nothing wrong with the method used in the other answer, but I want to show you how you can get the number of moles of helium without doing that many conversions.

You that your balloon has a radius of **18 cm**. You can determine its volume in

Use the fact that

Now use the ideal gas law equation to solve for *L atm/mol K*

To get the mass of helium, use its molar mass, which expresses the mass of *1 mole* of helium