Exercises: Separation of Solutions and Mixtures
Name a physical property that differs between the components of each mixture and that can be used to separate them: (a) ethanol and water, (b) sand and salt dissolved in…
Name a physical property that differs between the components of each mixture and that can be used to separate them: (a) ethanol and water, (b) sand and salt dissolved in water, (c) the colored pigments in a marker ink.
In paper chromatography, what are the stationary phase and the mobile phase? Which component of a mixture moves farther up the paper: the one more attracted to the paper…
In paper chromatography, what are the stationary phase and the mobile phase? Which component of a mixture moves farther up the paper: the one more attracted to the paper or the one more attracted to the solvent?
In a paper chromatography experiment, a dye spot traveled 3.0 cm while the solvent front traveled 6.0 cm from the starting line. Calculate the retention factor ($R_f$)…
In a paper chromatography experiment, a dye spot traveled 3.0 cm while the solvent front traveled 6.0 cm from the starting line. Calculate the retention factor ($R_f$) of the dye.
Emma runs a paper chromatogram of a green ink. The solvent front moves 8.0 cm. The yellow component moves 6.4 cm and the blue component moves 2.0 cm. (a) Calculate the…
Emma runs a paper chromatogram of a green ink. The solvent front moves 8.0 cm. The yellow component moves 6.4 cm and the blue component moves 2.0 cm. (a) Calculate the $R_f$ value of each component. (b) Which component has stronger attractions to the polar paper? Explain.
A mixture of hexane ($\text{C}6\text{H}{14}$, nonpolar) and ethanol ($\text{C}2\text{H}5\text{OH}$, hydrogen bonding) is separated by simple distillation. Which…
A mixture of hexane ($\text{C}_6\text{H}_{14}$, nonpolar) and ethanol ($\text{C}_2\text{H}_5\text{OH}$, hydrogen bonding) is separated by simple distillation. Which substance distills first? Explain in terms of intermolecular forces and boiling point.
In column chromatography, a polar silica gel column is used to separate a nonpolar compound A from a polar compound B using a nonpolar solvent. Which compound exits the…
In column chromatography, a polar silica gel column is used to separate a nonpolar compound A from a polar compound B using a nonpolar solvent. Which compound exits the column first? Explain, and describe what would happen if the solvent were changed to a much more polar one.
A student separates three compounds on a polar silica TLC plate using a nonpolar solvent. The solvent front travels 7.5 cm. Compound P travels 6.0 cm, compound Q travels…
A student separates three compounds on a polar silica TLC plate using a nonpolar solvent. The solvent front travels 7.5 cm. Compound P travels 6.0 cm, compound Q travels 3.0 cm, and compound R travels 0.75 cm. (a) Calculate each $R_f$. (b) Rank the compounds from least polar to most polar and justify using intermolecular forces. (c) Predict how the $R_f$ values would change if a more polar solvent were used, and explain.
A mixture contains water (boiling point 100 °C), ethanol (78 °C), and dissolved sodium chloride. (a) Describe a sequence of separation steps to isolate pure ethanol and…
A mixture contains water (boiling point 100 °C), ethanol (78 °C), and dissolved sodium chloride. (a) Describe a sequence of separation steps to isolate pure ethanol and recover the salt. (b) Explain, in terms of particle-level forces, why ethanol boils at a lower temperature than water and why the salt does not distill. (c) Explain why a single simple distillation of an ethanol–water mixture does not give 100% pure ethanol.