Stoichiometry Questions

• Steam distillation of immiscible liquids: Pure toluene boils at 110.6°C, pure water at 100°C. Toluene and water are immiscible. In a well-agitated equimolar mixture boiling at 1 atm (sum of vapour pressures = 1 atm), the mole fraction of water in the vapour phase (Xw) will satisfy:
• Reference state convention: Normal Temperature and Pressure (NTP) corresponds to which pair of conditions?
• Vapour pressure trend (revisited): For liquids of similar chemical nature at a given temperature, vapour pressure generally ________ with increasing molecular weight.
• Rate law inference: For the reaction X → Y, tripling [X] increases the rate ninefold. What is the order of the reaction with respect to X?
• Adsorption energetics: For physical adsorption dominated by van der Waals attraction and capillarity, the heat of adsorption is approximately equal to the heat of ________.
• Fuel gas usage problem (NTP basis): From 1 kg of calcium carbide (CaC2), about 0.41 kg of acetylene (C2H2) is produced with water. If an acetylene lamp burns 35 litres of gas per hour at NTP, how many hours of service are obtained from 1 kg CaC2?
• Real-gas compressibility factor Z (defined as actual volume / ideal-gas-predicted volume): As the pressure of the gas approaches 0 (very low-pressure limit), to what value does Z tend?
• Thermodynamics of NO and NO2 at 298 K: Given N2 + 2 O2 → 2 NO2 has ΔG° = 100 kJ per reaction (i.e., 50 kJ per mol NO2), and NO + 1/2 O2 → NO2 has ΔG° = -35 kJ per mol NO2, determine the standard free energy of formation of NO (kJ/mol).
• Unsteady leaching from porous solids: A long cylinder (5 cm diameter, flat ends sealed) and a sphere (5 cm diameter) are made from the same porous material and equally saturated with NaCl solution. Both are dipped for a short, equal time in a large, well-agitated water tank. If Xc and Xs are the fractions of salt remaining in the cylinder and sphere, which relation holds?
• Heat capacities of gases: At which absolute temperature condition can Cp equal Cv for a substance?
• Law of corresponding states: At equal reduced pressure and equal reduced temperature (corresponding states), which property of different gases is nearly the same?
• Unit conversion (kinematic viscosity): 1 m^2/s is equal to how many stokes (1 stoke = 1 cm^2/s)?
• Boiling-point elevation (colligative property): Compared with the pure solvent, the boiling point of a solution containing a nonvolatile solute is
• Avogadro’s number definition: Avogadro number is the number of molecules contained in one __________ of a gas (i.e., one chemical mole).
• Direction of solvent flow in osmosis: Across a semi-permeable membrane, the diffusion of which component goes in which direction?
• Stoichiometric methane combustion with air (all gaseous products): For CH4 + 2 O2 → CO2 + 2 H2O with stoichiometric air (21% O2, 79% N2 by volume), what is the water vapour mole fraction in the product mixture?
• Raoult’s law and ideality: Raoult’s law is exactly obeyed by which type of liquid solution under the same temperature and pressure conditions?
• Viscosity of dry atmospheric air: At room temperature (around 20–25°C), the dynamic viscosity of air is approximately what value in centipoise (cP)?
• Atomic number vs. other atomic properties: Which property of an element is always a whole number by definition?
• Unit conversion check (energy and power): Identify the incorrect conversion among the following commonly used engineering unit relations.