Question

1. How many moles of O2 are originally in a balloon if the initial volume is 1.00 L and the final volume is 0.67 L.  The final number of moles in the balloon is 8.0 moles.

Answer 1

According to the ideal gas law:

pV = nRT

where p- pressure, V - volume, n - number of moles, R - gas constant, T - temperature.

As temperature and pressure are constant:

V/n = RTp

From here:

V₁/n₁ = V₂/n₂

Finally:

n₁ = V₁n₂ / V₂ = 1.00 L × 8.0 mol / 0.67 L = 12 mol

Answer: 12 mol