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Molecular mass: Quiz


Question 1: The average molecular mass and the molar mass of a particular substance in a particular sample are in fact ________ identical and may be interconverted by Avogadro's constant.
CalculusOptimization (mathematics)Mathematical analysisNumerical analysis

Question 2: The average molecular mass is the abundance weighted ________ (average) of the molecular masses in a sample.
VarianceArithmetic meanStandard deviationMean

Question 3: Because a mole of molecules may contain a variety of molecular masses due to natural ________, the average mass is usually not identical to the mass of any single molecule.
IsotopeAtomStable nuclideTechnetium

Question 4: The difference of 0.00472 u or 0.03% comes from the fact that natural water contain traces of water molecules containing, oxygen-17, oxygen-18 or hydrogen-2 (________) atoms.

Question 5: The molecular mass can also be measured directly using ________.
AutopsyEnzyme assayChromatographyMass spectrometry

Question 6: However, the exact mass of hydrogen-1 (the most common hydrogen ________) is 1.00783, and the exact mass of oxygen-16 (the most common oxygen isotope) is 15.9949, so the mass of the most common molecule of water is 18.01056 u.
Stable nuclideAtomIsotopeTechnetium

Question 7: There are also situations where the isotopic distributions are not typical such as with ________ used in some nuclear reactors which is artificially enriched with Deuterium.
PlutoniumHeavy waterUraniumNuclear reactor technology

Question 8: The average atomic mass of natural ________ is 1.00794 u and that of natural oxygen is 15.9994 u; therefore, the molecular mass of natural water with formula H2O is (2 × 1.00794 u) + 15.9994 u = 18.01528 u.

Question 9: The molecular mass can be calculated as the sum of the individual ________ (as found in a table of isotopes) of all the atoms in any molecule.
Molar massChemistryOxygenAtomic mass

Question 10: Molecular mass differs from more common measurements of the mass of chemicals, such as ________, by taking into account the isotopic composition of a molecule rather than the average isotopic distribution of many molecules.
Molar massAtomHydrogenAtomic mass


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