Question

(a) Use these data to plot solubility as a function of temperature for \(\mathrm{KCl}\) and \(\mathrm{Li}_{2} \mathrm{SO}_{4}:\) (b) Using the plot, estimate the solubility of both compounds in water at \(70^{\circ} \mathrm{C}\). (c) How much of each compound can be dissolved in a beaker containing \(75 \mathrm{~g}\) of water at \(70^{\circ} \mathrm{C} ?\)

Short answer

Based on the plotted solubility graph, the estimated solubility of KCl at 70°C is \(A_{KCl}\) g/100g H2O and of Li2SO4 is \(A_{Li2SO4}\) g/100g H2O. In 75g water, the amount of KCl that can dissolve is: Amount of KCl = \(\frac{A_{KCl} \times 75}{100}\) g The amount of Li2SO4 that can dissolve is: Amount of Li2SO4 = \(\frac{A_{Li2SO4} \times 75}{100}\) g Replace \(A_{KCl}\) and \(A_{Li2SO4}\) with their estimated solubility values from the graph to obtain the amount of each compound that can be dissolved in 75g of water at 70°C.

Step-by-step solution

Plot the solubility of KCl and Li2SO4 as a function of temperature

First, we need to create a graph with temperature on the x-axis and solubility (in g/100g H2O) on the y-axis. Using the given data, plot the solubility of KCl and Li2SO4 at various temperatures. Connect the data points for each compound with a smooth curve to observe the trends.

Estimate the solubility of both compounds at 70°C

From the graph created in Step 1, find the solubility of KCl and Li2SO4 at 70°C by locating the point on the curve that corresponds to 70°C on the x-axis. Read the solubility value from the y-axis for both compounds.

Calculate the amount of each compound that can be dissolved in 75g of water at 70°C

Based on the solubility values obtained in Step 2, calculate the amount of KCl and Li2SO4 that can be dissolved in 75g of water at 70°C, using the formula: Amount of compound = (Solubility in g/100g H2O) × (mass of water/100g) Calculate the amount of KCl and Li2SO4 separately by substituting their respective solubility values and the mass of water (75g).

Key concepts

Solubility Curves

Understanding the relationship between solubility and temperature for various substances is fundamental in chemistry and can be visualized with the help of solubility curves. A solubility curve represents how the solubility of a substance in water changes as temperature varies. To construct these graphs, chemists plot the solubility (usually in grams of solute per 100 grams of water) on the y-axis against the temperature on the x-axis.

Each point on a solubility curve indicates how much of a substance can dissolve in 100 grams of water at a specific temperature. When creating the graph, there are noticeable trends. Generally, as the temperature increases, so does the solubility for many compounds. However, there are exceptions to this rule, which is why solubility curves are so vital for accurate predictions.

Using these curves, we can predict not only the solubility at a given temperature but also how a solution will behave when the temperature changes—for example, whether a precipitate will form upon cooling.

Estimating Solubility

Estimating solubility from a graph is a valuable skill that can help predict the amount of a substance that will dissolve in water at a given temperature. After plotting the solubility curve, one can locate a specific temperature on the x-axis and then read the corresponding solubility on the y-axis. This method gives an approximate value of the substance's solubility at that temperature.

Estimation is particularly useful when specific data points are not provided. It's important to be aware of the precision of the graph. That is, the closer the data points and the more detailed the scale, the more accurate the estimation. In practical applications, such as in the laboratory or industry, understanding this estimation process can help in determining the ideal conditions for a reaction or a process involving solutions.

Solving Chemistry Problems

Addressing chemistry problems typically involves a systematic approach of several steps: gathering data, identifying what is being asked, comprehending the principles at work, and executing the right calculations.

For example, to solve solubility problems: first, you need pertinent data, like solubility at different temperatures. Next, you define what you need to find out—such as the solubility at a specific temperature or the amount of solute that will dissolve in a given amount of solvent. Understanding the concept of solubility and its temperature dependence is crucial. Finally, you apply formulas and concepts (such as solubility curves) to calculate the answer. This structured approach lays the foundation for thoroughly and efficiently solving a variety of chemistry problems.

Chemical Solubility in Water

Chemical solubility in water is a core concept in chemistry that refers to the maximum amount of a substance (solute) that can dissolve in water (solvent) at a specific temperature and pressure to form a homogeneous solution. The solubility can be expressed in various ways, often in grams of solute per 100 grams of water. This property is essential for understanding reactions in aqueous solutions, processing pharmaceuticals, and managing environmental contamination.

The solubility depends on intermolecular interactions between the solute and solvent molecules as well as temperature and pressure. For instance, increasing temperature often increases solubility for solids and liquids but decreases it for gases. Water's polarity makes it an excellent solvent, capable of dissolving many substances due to its ability to establish hydrogen bonds with solutes, thus enhancing their solubility.