A laboratory technician is preparing a demonstration to illustrate the connection…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A laboratory technician is preparing a demonstration to illustrate the connection between individual atoms and the macroscopic masses handled in the lab.
The technician selects pure magnesium metal because its reactivity is easily observed when ignited. A clean ribbon of magnesium is cut so that its mass is exactly 2.35g.
Use the following average atomic masses (in atomic mass units, amu):
Mg = 24.31, C = 12.01, H = 1.008, O = 16.00.
Answer the following questions.
(a) Describe, in words, the quantitative relationship between an element’s average atomic mass in amu and its molar mass expressed in grams per mole.
(b) Explain how Avogadro’s number bridges the microscopic scale (individual atoms) and the macroscopic scale (measurable masses) for the sample described.
(c) Calculate the amount of substance, in moles, present in the 2.35g sample of magnesium. Report your answer with the correct number of significant figures.
(d) If the technician were instead to use a 2.35g sample of carbon, would the number of atoms in the carbon sample be greater than, less than, or equal to the number of atoms in the 2.35g magnesium sample? Justify your answer quantitatively.