We have a tank that contains O2 at 146 mmHg, N2 at 146 mmHg, and CO2 at 138 mmHg. We then add 135 mmHg of Ar. What is the pressure in the tank?

To find the total pressure in the tank, you need to add up the partial pressures of each gas. The partial pressure of a gas can be calculated by multiplying the mole fraction of the gas by the total pressure.

First, let's calculate the mole fraction of each gas. The mole fraction is the ratio of the number of moles of a gas to the total number of moles of all gases.

For O2:
Mole fraction of O2 = moles of O2 / total moles
Since the mole fraction of each gas is directly proportional to its partial pressure, we can use the given pressures as representative of the mole fraction.
Mole fraction of O2 = 146 mmHg / (146 mmHg + 146 mmHg + 138 mmHg + 135 mmHg)

For N2:
Mole fraction of N2 = 146 mmHg / (146 mmHg + 146 mmHg + 138 mmHg + 135 mmHg)

For CO2:
Mole fraction of CO2 = 138 mmHg / (146 mmHg + 146 mmHg + 138 mmHg + 135 mmHg)

For Ar:
Mole fraction of Ar = 135 mmHg / (146 mmHg + 146 mmHg + 138 mmHg + 135 mmHg)

Now, let's calculate the total pressure in the tank by summing the partial pressures:
Total pressure = (Mole fraction of O2 * Total pressure) + (Mole fraction of N2 * Total pressure) + (Mole fraction of CO2 * Total pressure) + (Mole fraction of Ar * Total pressure)

Since we know the mole fractions and have the values of the other gases' pressures, we can substitute these values into the equation and solve for the total pressure.