A gas mixture with a total pressure of 755 mmHg contains each of the following gases at the indicated partial pressure: 126 mmHg CO2, 224 mmHg Ar, and 177 mmHg O2. The mixture also contains helium gas. What is the partial pressure of the helium gas?
a) 228 mmHg
b) 227 mmHg
c) 229 mmHg
d) 230 mmHg
