# Determine the total pressure of a gas mixture that contains oxygen, nitrogen, and helium if the partial pressures of the gases are as follows: #"P"_ ("O"_ 2) = "20.0 kPa"#, #P_ ("N"_ 2) = "46.7 kPa"#, and #P_ "He" = "26.7 kPa"# ?

##### 1 Answer

#### Explanation:

The idea here is that the **total pressure** of the gaseous mixture will be equal to the sum of the *partial pressures* of the constituent gases **Dalton's Law of Partial Pressures** here.

In other words, if you add the pressure that each gas would exert **if alone** in the container, you get the **total pressure** of the mixture.

So for a mixture that contains

#P_"total" = sum_i P_i#

In your case, the mixture contains three gases: oxygen gas, nitrogen gas, and helium. Moreover, you know that

#P_( "O"_ 2) = "20.0 kPa"# #P_ ("N"_ 2) = "46.7 kPa"# #P_ "he" = "26.7 kPa"#

This means that the **total pressure** of the gas is given by

#P_"total" = P_ ("O"_ 2) + P_ ("N"_ 2) + P_ "He"#

which is equal to

#P_"total" = "20.0 kPa" + "46.7 kPa" + "26.7 kPa"#

#color(darkgreen)(ul(color(black)(P_"total" = "93.4 kPa")))#