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**1. Homework Statement**

A spherical balloon is inflated to a diameter of 36 cm. Assuming that the gas in the balloon is of atmospheric pressure (101.3 kPa) and is at a temperature of 20°C.

(a) How many moles of gas are in the balloon?

(b) If 21% of the molecules in the balloon are oxygen molecules, how many oxygen molecules are in the balloon?

**3. The Attempt at a Solution**

(a) I want to use the formula [tex]PV=nRT[/tex]

Volume is [tex]v=\frac{4}{3} \pi (0.18)^2 = 0.1357[/tex]

R is the constant 8.314

So [tex](101.3)(0.1357)=n8.314(20)[/tex]

Now if I solve for n I get [tex]n= {13.74}{166.28} = 0.082[/tex]

This is wrong because the correct answer must be

**1.02**. Do I need to convert the temprature to Kelvin/absolute temprature? ...because I tried that too & it didn't work.