Students attempted to recover solid NaCl by pouring saltwater through quantitative…
CHEMISTRY · Single correct · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Students attempted to recover solid NaCl by pouring saltwater through quantitative filter paper with a nominal pore diameter of about 2μm. No residue was collected. Which of the following best explains the failure of this separation attempt?
(a) Because the solution was unsaturated, no solid NaCl was present to be trapped; only a saturated solution would form filterable crystals.
(b) NaCl crystals are denser than water, so gravity pulls them through the 2μm pores instead of allowing them to stay on the filter paper.
(c) Dissolved NaCl exists as individual hydrated ions whose diameters are far smaller than the filter pores, so the ions move through the paper with the solvent.
(d) Any NaCl crystals that reached the filter redissolved due to capillary action and water held in the paper, letting them pass through the pores.