Gas Laws, Mixtures, and Reaction Stoichiometry

All flashcards

What is the ideal gas law?

$PV=nRT$, relating pressure, volume, amount in moles, and absolute temperature.

How is gas density related to molar mass and gas conditions?

For an ideal gas, $d=MP/(RT)$. Density increases with molar mass or pressure and decreases with temperature.

How can the molar mass of an unknown gas be determined experimentally?

Measure its mass, pressure, volume, and temperature, then use $M=mRT/(PV)$ with consistent units.

What is the difference between empirical and molecular formulas?

An empirical formula gives the simplest whole-number atom ratio; a molecular formula gives the actual atom count in a molecule.

How do you convert an empirical formula into a molecular formula?

Divide the measured molar mass by the empirical formula mass to find an integer multiplier, then multiply every empirical-formula subscript by it.

Quiz questions

1. According to Dalton's law, how is the total pressure of a nonreacting gas mixture calculated?Answer: Add the partial pressures of all components.
2. A gas mixture has total pressure $P_{total}$ and component A has mole fraction $X_A$. Which equation gives A's partial pressure?Answer: $P_A=X_A P_{total}$
3. A gas collected over water has total pressure $P_{total}$ and water-vapor pressure $P_{H_2O}$. Which expression gives the dry-gas pressure?Answer: $P_{gas}=P_{total}-P_{H_2O}$
4. For a balanced reaction, when can its coefficients be used directly as gas-volume ratios?Answer: When all gas volumes are measured at the same temperature and pressure.
5. In a reaction calculation, a reactant amount is given as a mass and a product amount is needed in moles. What should be done first?Answer: Convert the reactant mass to moles using its molar mass.