Question

14. A 500.0 ml flask contained O2 gas at 25.0°C at a pressure of 4.5 atm. What is the number

of moles in the flask?

Answer 1

Step-by-step explanation:

3.Apply the ideal gas law: PV = nRT solving for n. Here you can use the pressure given in atm, but you must choose the 0.0821 atm L/mole K gas constant. Or you can change 4.5 atm to 3420 mm Hg and use the 62.4 mmHg L/mole K gas constant. You must change 500 ml to 0.5 L because both gas constants have units in L, and so the volume must be in liters so it can cancel out. And of course, you must change the temperature to Kelvin.

a. n = (4.5atm)(0.5L)

moliK)(298K) = 0.092 mole (0.0821 atmiL

b. 0.092mol 32g

⎛⎝⎜ ⎞⎠⎟ = 2.9 g

1mol

c. Remember that D = mass

vol so D = 2.9g

0.5L = 5.9 g/L