What is the total pressure in of a gas mixture containing argon gas at 0.25 , helium gas at 385 , and nitrogen gas at 345 .

You don't have any units on those numbers.

To find the total pressure of a gas mixture containing different gases, we need to first understand Dalton's law of partial pressures. According to this law, the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of each gas.

In this case, we have three different gases: argon (Ar), helium (He), and nitrogen (N2). Each gas exerts a partial pressure, which is the pressure that gas would exert if it occupied the entire volume on its own.

We are given the partial pressures of each gas:
- argon gas (Ar) has a partial pressure of 0.25 atm
- helium gas (He) has a partial pressure of 385 atm
- nitrogen gas (N2) has a partial pressure of 345 atm

To find the total pressure, we simply add up the partial pressures of each gas:

Total pressure = Partial pressure of Ar + Partial pressure of He + Partial pressure of N2

Plugging in the given values:
Total pressure = 0.25 atm + 385 atm + 345 atm

Calculating the expression:
Total pressure = 730.25 atm

Therefore, the total pressure in the gas mixture is 730.25 atm.