Question

The density of O2 is 1.43 g/L at STP. Find the density at 70.0°C and 840 mmHg.

a) 1.43 g/L
b) 1.58 g/L
c) 1.35 g/L
d) 1.29 g/L

Answer 1

By applying the combined gas law, the density of O2 at 70.0°C and 840 mmHg is calculated to be approximately 1.29 g/L.

Step-by-step explanation:

This question involves applying the Gas Laws to determine the density of a gas under changed conditions of temperature and pressure. Since density is directly proportional to pressure and inversely proportional to temperature (via the Ideal Gas Law), we can use the combined gas law to solve for the new density:

The combined gas law is P1/T1 = P2/T2, where P is pressure and T is temperature (in Kelvins). The density of a gas changes with conditions according to the formula d1/P1*T2 = d2/P2*T1, where d1 and d2 are the densities under two different sets of conditions.

To answer the question:

1. Convert the given temperature to Kelvin: T2 = 70.0°C + 273.15 = 343.15 K.
2. Convert the given pressure to atmospheres: P2 = 840 mmHg * (1 atm / 760 mmHg) = 1.10526 atm.
3. Plug in the values: (1.43 g/L / 1 atm) * (273.15 K / 343.15 K) * 1.10526 atm = 1.29 g/L.

Thus, the new density at 70.0°C and 840 mmHg is approximately 1.29 g/L, which corresponds to choice (d).