7. A mixture of oxygen, nitrogen, and hydrogen gases exert a total pressure of 740 torr at 0°C. The partial
pressure of oxygen is 200 torr and the partial pressure of nitrogen is 400 torr. What is the partial pressure
of hydrogen gas in the mixture?
a. 140 torr
b. 200 torr
c. 740 torr
d. 1,340 torr