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QLDChemistryQuick questions
Unit 2: Molecular interactions and reactions
Quick questions on The ideal gas equation and molar volume (QCE Chemistry Unit 2)
9short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What is units for QCE Chemistry?Show answer
QCAA's chemistry data sheet supplies R in J/(mol K) and defines standard conditions for chemistry. With these units, products PV come out in joules, matching the energy units of nRT.
What is molar volume of a gas?Show answer
The molar volume V_m is the volume occupied by 1 mol of an ideal gas at a specified pressure and temperature.
What is rearranging PV = nRT?Show answer
Solve for any single variable:
What is worked example?Show answer
What is the density of nitrogen gas, N_2, at SLC?
What is forgetting Kelvin?Show answer
Using degrees C in PV = nRT gives wrong answers and sometimes negative results. Always convert.
What is wrong R for the unit set?Show answer
Use R = 8.314 J/(mol K) with kPa and L. Using R = 0.0821 L atm /(mol K) with kPa will be off by a factor of 100.
What is treating SLC and STP as the same?Show answer
They are not. SLC is 25 degrees C, 100 kPa, V_m = 24.79 L/mol. The classic 22.4 L/mol value uses old STP (0 degrees C, 1 atm).
What is confusing V_m with M?Show answer
V_m is litres per mole (a volume). M is grams per mole (a mass). They are independent and both needed when converting between mass and volume of a gas.
What is reporting too many significant figures?Show answer
Match the input data, typically 3 sig fig in QCAA problems.