Solubility

Overview

Engineering reference data for Solubility in miscellaneous.

Key Formulas

Unit Conversion

$y = x \cdot k$

Multiply by conversion factor.

Linear Interpolation

$y = y_1 + \frac{(x - x_1)(y_2 - y_1)}{x_2 - x_1}$

Estimate between two known points.

Percentage

$p = \frac{\text{part}}{\text{whole}} \times 100\%$

Part as fraction of whole.

Variables

Symbol	Description	Unit
$x$	Input value	—
$y$	Output value	—
$k$	Conversion factor	—

Factors Affecting Solubility

• Solubility generally increases with temperature (though with exceptions).
• Smaller particles dissolve faster than larger particles.
• Stirring or shaking a mixture increases the rate of dissolving.

Example Calculations

The weight percent (wt%) concentration of a solution is calculated using:

$$\text{Concentration (wt\%)} = \frac{\text{Mass of solute (g)}}{\text{Mass of solute (g)} + \text{Mass of solvent (g)}} \times 100\%$$

Example 1: Problem: Sodium chloride (NaCl) has a solubility of 36 g in 100 g of water at 25°C. What is the concentration (wt%) of the saturated solution? Solution: A saturated solution contains the maximum solute.

$$\text{NaCl concentration} = \frac{36}{36 + 100} \times 100\% = 26.5 \text{ wt\%}$$

Example 2: Problem: What is the concentration (wt%) if 34 g NaCl is added to 100 g of water at 25°C? Solution: 34 g is less than the solubility (36 g), so all salt dissolves.

$$\text{NaCl concentration} = \frac{34}{34 + 100} \times 100\% = 25.4 \text{ wt\%}$$

Example 3: Problem: What is the concentration (wt%) if 38 g NaCl is added to 100 g of water at 25°C? Solution: 38 g exceeds the solubility. The solution becomes saturated, and 2 g of salt remains undissolved. The concentration is that of the saturated solution:

$$\text{NaCl concentration} = \frac{36}{36 + 100} \times 100\% = 26.5 \text{ wt\%}$$

References

• Original Source