To determine the molecular formula of the oxide of arsenic in its gaseous state, you can use the ideal gas law equation: PV = nRT.
1. Convert the given pressure from mm Hg to atmospheres: 890 mm Hg / 760 mm Hg/atm = 1.17 atm.
2. Convert the given volume from cm³ to liters: 194 cm³ / 1000 cm³/L = 0.194 L.
3. Rearrange the ideal gas law equation to solve for the number of moles (n):
n = PV / RT.
4. Substitute the given values into the equation:
n = (1.17 atm) * (0.194 L) / [(0.08206 L*atm/mol*K) * (273 K + 650 °C)].
5. Simplify and calculate the value of n.
Next, you can use the molar mass of the sample and the number of moles obtained to determine the molecular formula.
1. Calculate the number of moles using the formula:
moles = grams / molar mass.
2. Substitute the given values into the equation:
moles = 0.927 g / molar mass.
3. Rearrange the equation to solve for the molar mass:
molar mass = grams / moles.
4. Substitute the calculated values from earlier into the equation to determine the molar mass of the oxide.
Finally, the molecular formula of the oxide of arsenic can be determined by comparing the molar mass obtained with the known masses of different compounds and their respective molecular formulas.