A materials science team fabricates nanocrystalline copper particles and seeks to…
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A materials science team fabricates nanocrystalline copper particles and seeks to verify the purity of the product. Using a highly sensitive microbalance, the team determines that a batch of the particles has a mass of 18.95 mg. An independent particle-counting technique indicates that the batch contains (1.76±0.05)×1020 copper atoms.
For copper, the literature molar mass is 63.55 g mol⁻¹ and Avogadro’s constant is NA=6.022×1023mol−1.
(a) Calculate the experimental molar mass of the copper obtained from the measured mass and the central (best-estimate) particle count.
(b) Determine the percent error of the experimental molar mass with respect to the literature value.
(c) Propagate the uncertainty in the particle count through your calculation in part (a) and report the experimental molar mass with its associated uncertainty.
(d) Based on your results in parts (b) and (c), assess whether the experimental data are consistent with the particles being pure copper at the 95 % confidence level. Provide a clear quantitative justification.