The density of toluene (C7H8) is 0.867 g/mL, and the density of thiophene (C4H4S) is 1.065 g/mL. A solution is made by dissolving 8.10 g of thiophene in 250.0 mL of toluene. Assuming that the volumes of the solute and solvent are additive, what is the molarity of thiophene in the solution?

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Calculate the volume of thiophene using its mass and density. Use the formula: \( \text{Volume} = \frac{\text{Mass}}{\text{Density}} \).

Determine the total volume of the solution by adding the volume of thiophene to the volume of toluene.

Calculate the number of moles of thiophene using its mass and molar mass. Use the formula: \( \text{Moles} = \frac{\text{Mass}}{\text{Molar Mass}} \).

Use the total volume of the solution (in liters) and the moles of thiophene to calculate the molarity. Use the formula: \( \text{Molarity} = \frac{\text{Moles of Solute}}{\text{Volume of Solution in Liters}} \).

Ensure all units are consistent, particularly converting mL to L for the volume of the solution.

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Textbook Question

This figure shows the interaction of a cation with surrounding water molecules. (b) Which of the following explanations accounts for the fact that the ion–solvent interaction is greater for Li⁺ than for K⁺? a. Li⁺ is of lower mass than K⁺. b. The ionization energy of Li is higher than that for K. c. Li⁺ has a smaller ionic radius than K⁺. d. Li has a lower density than K. e. Li reacts with water more slowly than K. [Section 13.1]

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Textbook Question

Consider two ionic solids, both composed of singly charged ions, that have different lattice energies. (b) If not, which solid will be more soluble in water, the one with the larger lattice energy or the one with the smaller lattice energy? Assume that solute–solvent interactions are the same for both solids. [Section 13.1]

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Open Question

Which two statements about gas mixtures are true? [Section 13.1] (a) Gases always mix with other gases because the gas particles are too far apart to feel significant intermolecular attractions or repulsions. (b) Just like water and oil don’t mix in the liquid phase, two gases can be immiscible and not mix in the gas phase. (c) If you cool a gaseous mixture, you will liquefy all the gases at the same temperature. (d) Gases mix in all proportions in part because the entropy of the system increases upon doing so.

Open Question

If you compare the solubilities of the noble gases in water, you find that solubility increases from smallest atomic weight to largest, specifically: Ar < Kr < Xe. Which of the following statements is the best explanation? [Section 13.3] (a) The heavier the gas, the more it sinks to the bottom of the water and leaves room for more gas molecules at the top of the water. (b) The heavier the gas, the more dispersion forces it has, and therefore the more attractive interactions it has with water molecules. (c) The heavier the gas, the more likely it is to hydrogen-bond with water. (d) The heavier the gas, the more likely it is to make a saturated solution in water.

Textbook Question

The structures of vitamins E and B6 are shown below. Predict which is more water soluble and which is more fat soluble. [Section 13.3]

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Open Question

You take a sample of water that is at room temperature and in contact with air and put it under a vacuum. Right away, you see bubbles leave the water, but after a little while, the bubbles stop. As you keep applying the vacuum, more bubbles appear. A friend tells you that the first bubbles were water vapor, and that the low pressure had reduced the boiling point of water, causing the water to boil. Another friend tells you that the first bubbles were gas molecules from the air (oxygen, nitrogen, and so forth) that were dissolved in the water. Which friend is most likely to be correct? What, then, is responsible for the second batch of bubbles? [Section 13.4]