A mixture of 1.41 g of oxygen and 1.66 g of helium has a total pressure of 4.34 atm. What is the partial pressure of the He gas?

To solve this problem, we need to use Dalton's Law of Partial Pressures, which states that the total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.

Step 1: Calculate the number of moles of each gas.

The molar mass of oxygen (O2) is approximately 32 g/mol, and the molar mass of helium (He) is approximately 4 g/mol.

For oxygen: Number of moles = mass / molar mass = 1.41 g / 32 g/mol = 0.0441 mol

For helium: Number of moles = mass / molar mass = 1.66 g / 4 g/mol = 0.415 mol

Step 2: Calculate the total number of moles.

Total moles = moles of O2 + moles of He = 0.0441 mol + 0.415 mol = 0.4591 mol

Step 3: Calculate the mole fraction of each gas.

The mole fraction is calculated by dividing the number of moles of a gas by the total number of moles.

For helium: Mole fraction = moles of He / total moles = 0.415 mol / 0.4591 mol = 0.904

Step 4: Calculate the partial pressure of each gas.

The partial pressure is calculated by multiplying the mole fraction of a gas by the total pressure.

For helium: Partial pressure = mole fraction of He * total pressure = 0.904 * 4.34 atm = 3.92 atm

So, the partial pressure of the helium gas in the mixture is approximately 3.92 atm.