91影视

Deviations from Raoult鈥檚 law lead to the formation of azeotropes, constant boiling mixtures that cannot be separated by distillation, making industrial separations difficult. For components A and B, there is a positive deviation if the A-B attraction is less than A-A and B-B attractions (A and B reject each other), and a negative deviation if the A-B attraction is greater than A-A and B-B attractions. If the A-B attraction is nearly equal to the A-A and B-B attractions, the solution obeys Raoult鈥檚 law. Explain whether the behavior of each pair will be nearly ideal, have a positive deviation, or a negative deviation:

(a) Benzene $\mathbf{\left(}{\mathbf{\text{C}}}_{\mathbf{\text{6}}}{\mathbf{\text{H}}}_{\mathbf{\text{6}}}\mathbf{\right)}$and methanol;

(b) Water and ethyl acetate;

(c) Hexane and heptane;

(d) Methanol and water;

(e) Water and hydrochloric acid.

Calculate the molality, molarity, and mole fraction of $\mathit{F}\mathit{e}\mathit{C}{\mathit{l}}_{\mathbf{3}}$ in a 28.8 mass % aqueous solution (d = 1.280 g/mL).

Wastewater from a cement factory contains 0.25 g of ${\mathbf{Ca}}^{\mathbf{2}\mathbf{+}}$ion and 0.056 g of ${\mathbf{Mg}}^{\mathbf{2}\mathbf{+}}$ion per 100.0 L of solution. The solution density is 1.001 g/mL. Calculate the ${\mathbf{Ca}}^{\mathbf{2}\mathbf{+}}$and ${\mathbf{Mg}}^{\mathbf{2}\mathbf{+}}$ concentrations in ppm (by mass).

An automobile antifreeze mixture is made by mixing equal volumes of ethylene glycol (d = 1.114 g/mL; 杀 = 62.07 g/mole) and water (d = 1.00 g/mL) at ${\mathbf{20}}^{\mathbf{o}}\mathbf{C}$. The density of the mixture is 1.070g/mL. Express the concentration of ethylene glycol as:

(a) Volume percent

(b) Mass percent

(c) Molarity

(d) Molality

(e) Mole fraction

In what sense is a strong electrolyte 鈥渟trong鈥�? What property of the substance makes it a strong electrolyte?

Express Raoult鈥檚 law in words. Is Raoult鈥檚 law valid for a solution of a volatile solute? Explain.

What are the most important differences between the phase diagram of a pure solvent and the phase diagram of a solution of the solvent?

Which aqueous solution has a freezing point closer to its predicted value, 0.01 m NaBr or 0.01 m MgCl₂? Explain.

Question: Which solution has the lower freezing point?

(a)$\mathbf{11}\mathbf{.}\mathbf{0}{\mathbf{gofCH}}_{\mathbf{3}}\mathbf{OHin}\mathbf{100}\mathbf{.}\mathbf{gofH}\mathbf{2}\mathbf{Oor}\mathbf{22}\mathbf{.}\mathbf{0}{\mathbf{gofCH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OHin}\mathbf{200}\mathbf{.}\mathbf{gofH}\mathbf{2}\mathbf{O}$

(b)$\mathbf{20}\mathbf{.}\mathbf{0}{\mathbf{gofH}}_{\mathbf{2}}\mathbf{Oin}\mathbf{1}\mathbf{.}\mathbf{00}{\mathbf{kgofCH}}_{\mathbf{3}}\mathbf{OHor}\mathbf{20}\mathbf{.}\mathbf{0}{\mathbf{gofCH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}\mathbf{OHin}\mathbf{1}\mathbf{.}\mathbf{00}{\mathbf{kgofCH}}_{\mathbf{3}}\mathbf{OH}$

Which solution has the higher boiling point?

(a) 38.0 g of ${\mathbf{C}}_{\mathbf{3}}{\mathbf{H}}_{\mathbf{8}}{\mathbf{O}}_{\mathbf{3}}$ in 250. g of ethanol or 38.0 g of ${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{6}}{\mathbf{O}}_{\mathbf{2}}$in 250. g of ethanol

(b) 15 g of ${\mathbf{C}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{6}}{\mathbf{O}}_{\mathbf{2}}$ in 0.50 kg of ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$ or 15 g of NaCl in 0.50 kg of ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$.