A scientist is examining a mixture of nitrogen, hydrogen, and ammonia. The individual pressures that are exerted by nitrogen and hydrogen are 0.26 atm and 0.28 atm, respectively. If the total pressure is 0.90 atm, what is the partial pressure of ammonia?

Using Daltons Law which states that the total pressure of a gas mixture is the sum of the gasses partial pressure. Thus,

Pt (total pressure) = P1+P2+P3

where

Pt = 0.90 atm

P1 = 0.26 atm

P2 = 0.28 atm

P3 = ?

substitute the formula with known variables

P3 = 0.90 atm - (0.26atm+0.28atm)

P3 = 0.36 atm

The partial pressure of ammonia is 0.36 atm