Question

1. using the graph above, describe the connections between the temperature of a solvent and the solubility of a solute that is a solid. what would happen if a hot solution with a lot of solid in it cooled down?
2. how do polar and nonpolar substances differ? give an example of each. (p. 3)
3. compare the solubility of nacl and kcl at 70 degrees using the graph on p. 7.
4. why are carbonated beverages bottled with so much pressure? (p. 8)

Explanation:

Question 3

Step1: Analyze the graph trend

Observe the solubility curves of solid solutes (NH₄Cl, KCl, NaCl, KClO₃) as temperature (x - axis) increases. All curves show an upward slope, meaning solubility (y - axis, grams of solute per 100g H₂O) increases with temperature.

Step2: Predict cooling effect

For a hot, saturated (or nearly saturated) solution with excess solid, when cooled, the solubility decreases. Since the solution can't hold as much solute at lower temperatures, the excess solid solute will precipitate out (crystallize) from the solution.

Polar substances have a separation of electric charge (a dipole moment), meaning they have a positive and a negative end (e.g., water, $\ce{H2O}$, where oxygen is partially negative and hydrogens are partially positive). Nonpolar substances have an even distribution of charge (no dipole moment), with electrons shared equally or symmetrically (e.g., oil, or methane, $\ce{CH4}$). A key difference is in solubility: polar substances tend to dissolve in polar solvents (like water dissolves salt, a polar solute), and nonpolar substances tend to dissolve in nonpolar solvents (like oil dissolves in gasoline).

Step1: Locate 70°C on x - axis

Find the vertical line corresponding to 70°C on the temperature (x - axis) of the solubility graph.

Step2: Find solubility of NaCl and KCl

From the graph, at 70°C, the solubility curve of $\ce{NaCl}$ (the relatively flatter, red - brownish? or green? curve, depending on the graph's color coding) and $\ce{KCl}$ (the other curve). Visually, the solubility of $\ce{KCl}$ at 70°C is greater than the solubility of $\ce{NaCl}$ at 70°C. For example, if we estimate from the grid, at 70°C, $\ce{NaCl}$ solubility is around 37 - 38 g/100g $\ce{H2O}$, and $\ce{KCl}$ solubility is around 48 - 50 g/100g $\ce{H2O}$ (approximate values from typical solubility graphs for these salts at 70°C). So $\ce{KCl}$ is more soluble than $\ce{NaCl}$ at 70°C.

Answer:

For solid solutes (like the ones in the graph: $\ce{NH4Cl}$, $\ce{KCl}$, $\ce{NaCl}$, $\ce{KClO3}$), as the temperature of the solvent (water) increases, the solubility of the solid solute generally increases (all the solubility curves have a positive slope with increasing temperature). If a hot solution with a large amount of dissolved solid (a hot, nearly saturated or saturated solution) is cooled down, the solubility of the solid solute decreases. Since the solution can no longer hold the same amount of solute at the lower temperature, the excess solid solute will precipitate (crystallize) out of the solution.

Question 4