Identifying Unknown Substances Based on Solubility Data

In this article, we delve into the process of identifying an unknown substance based on its solubility data, particularly when 100 grams of the substance is dissolved in 100 mL of water at a temperature of 35°C. Understanding the solubility of substances and the factors that influence it can provide valuable insights into the identity of the substance in question.

Calculating the Concentration

First, let's calculate the concentration of the solution provided in the problem statement:

The concentration of the solution is given by:

$$frac{100 text{ grams}}{100 text{ mL}} 1 text{ g/mL}$$

Knowing the concentration, we can begin to narrow down the possible substances by considering the solubility of various common substances at 35°C.

Common Substances with High Solubility

Many salts and sugars can dissolve to achieve the concentration of 1 g/mL in 100 mL of water at 35°C. Some examples include:

Sodium Chloride (NaCl): Has a solubility of about 36 g/100 mL at 20°C and increases slightly at higher temperatures. Sucrose (Table Sugar, C12H22O11): Has a solubility of about 2000 g/100 mL at 25°C, which is much higher than 1 g/mL.

Given that the concentration is 1 g/mL, which is significantly lower than the solubility of sucrose, sodium chloride is a more likely candidate. However, it is important to note that other substances may also be considered depending on the specifics of the scenario.

Physical Properties and Temperature Effects

When considering the identity of the substance, it is crucial to take into account both physical properties and temperature effects:

Physical Properties: If the substance is a solid, additional information such as its taste, texture, appearance, and any special properties can help in identifying it. For instance, the taste and texture of the dissolved substance can provide initial clues, but these are often insufficient on their own. Temperature Effects: The solubility of many substances increases with temperature. Therefore, the temperature of 35°C might allow for a wider range of possible substances, as their solubility may be higher at this temperature than at others.

For instance, some salts like calcium nitrate (Ca(NO3)2) can dissolve to a concentration of 1200 g/L at 20°C. At 35°C, this concentration would be even higher, making it a viable candidate. Other salts like Rubidium Chloride (RbCl) and Rubidium Nitrate (RbNO3) both have solubilities just under 100 g/100 mL at 30°C and just over that at 40°C, making them possible candidates if the solution is saturated at 100 g per 100 mL.

Additionally, Barium Nitrite (Ba(NO2)2) has a solubility of 102 g at 40°C but drops to 72.8 g at 20°C, making it less likely to be the substance if the solubility gradient is significant.

Unsaturated Solutions

If the solution is not saturated, there are even more possibilities. Hundreds of compounds can dissolve more than 100 g/100 mL, so if the solution is not saturated, practically any of these substances could be the unknown.

Given the high solubility of many salts and sugars, Sodium Chloride (NaCl) and Sucrose (C12H22O11) are still strong candidates, but Calcium Nitrate (Ca(NO3)2) is a highly likely candidate as well due to its high solubility at 35°C.

Without additional information about the physical and chemical properties of the substance, it can be challenging to pinpoint the exact identity definitively. If more details about the characteristics or behavior of the substance in solution are available, a more specific identification can be made.

For further assistance or more precise identification, consider using a solubility table or consulting with a chemist for detailed analysis.