Factors Affecting Solubility Roque, Jason R. Rodrin, Lauro Niño M. Samoranos, Karizza Mae P. So, Bernard Allan M. Bachelor of Science in Biology – Major in Human Biology College of Science De La Salle University – Dasmariñas Dasmariñas, Cavite, Philippines
ABSTRACT
The experiment, factors affecting solubility, was demonstrated by using different solid and liquid samples. The gram samples of KCl and NaCl was placed in an ignition tube with water. The solution was shaken to determine the solubility of the samples. The same samples that is placed in the ignition tube with water, was gently heated to 80 oC using water bath. Again, the solution solution was shaken to determine the solubility of the samples. The solubility of a gram/ml of each sample of potassium nitrate, sodium chloride, coconut oil, toluene and copper sulfate was test by means of water, isopropyl alcohol, and the 1:1 ratio of water and isopropyl alcohol as solvent. Also, the effect of the polarity in the samples was noted. Lastly, a pinch of Iodine crystals was placed in a test tube with water and was shaken to determine its solubility. Afterwards, potassium iodide was added into the solution and the solubility was determined.
INTRODUCTION Solubility is the property of a solid, liquid, or gaseous or gaseous chemical substance called solute to dissolve in a liquid solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on temperature and pressure. The extent of the solubility of a substance in a specific solvent is measured as the saturation concentration where adding more solute does not increase the concentration of the solution. (1) The solvent is generally a liquid, which can be a pure substance or a mixture. (2) The extent of solubility ranges widely, from infinitely soluble (fully miscible) miscible) to poorly soluble. (3) The solubility of a solid in a liquid is most affected by temperature, nature of solute particles, and nature of the solvent particles. In general, an increase in temperature increases the solubility of a substance but there are some exceptions to this rule (4, 5) In case of gases, an increase in temperature decreases the solubility of gases in liquids while increased pressure increase their solubility. (6) These These are some some of the factor factors s that that will will affect affect the solubi solubili lity: ty: Temper Temperatu ature re basica basicall lly y increases the solubility for most of the solvents. solvents. The situation is though different for gases. With increase of the temperature they became less soluble in each other and in water, but more soluble in organic solvents. Next is the polarity. In most cases solutes dissolve in solvents that have a similar polarity. Chemists use a popular aphorism to describe this feature of solutes and solvents: "Like dissolves like" like". Nonpolar solutes do not dissolve in polar solvents and the other way aro around und.. Pr Press essure ure in sol solid, id, liquid liquid and gas sol solute utes s may als also o aff affect ect the sol solubi ubili lity. ty. Als Also, o,
molecular size will affect its solubility. The larger the molecules of the solute are the larger is their molecular weight and their size. It is more difficult for solvent molecules to surround bigger molecules. molec ules. If all of the above mentioned mentioned factors are excluded, excluded, a gener general al rule can be found that larger particles are generally less soluble. If the pressure and temperature are the same than out of two solu solutes tes of the same polar polarity, ity, the one with smal smaller ler particles particles is usually more solu soluble. ble. The stirring also increases the speed of solubility. Stirring does not have an effect on the solubility of a substance. Stirring only increases the speed of the process - it increases move of the solvent what supposes solute to fresh portions of it, thus enabling solubility. As molecules in liquid substances are in constant move, the process would take place anyway, but it would take more time.
MATERIALS / REAGENTS & EXPERIMENTAL PROCEDURE For the effect of temperature on solubility of a solid in water, we used 1 gram of KCL to 10mL water in an ignition tube. The solution shaken and the solubility were noted. Then the solution was gently heated to 40oC and stirred to determine its solubility. Another gram of KCl was added added to the same mixtu mixture. re. Then Then the mixtu mixture re was stirred stirred to determ determine ine its solubi solubili lity. ty. Afterwards, the mixture was heated to 80oC using a water bath. The mixture was shaken and the solubility was noted. For the effect effect of the polarity polarity of the solute solute and solvent, solvent, each gram/m gram/mL L sample samples s of potassium nitrate, sodium chloride, coconut oil, toluene and copper sulfate was added to the 1mL water, 1mL isopropyl alcohol and the ratio 1:1 of water and isopropyl alcohol. For the influence of another substance, a pinch of iodine crystal was place in 10mL water and was shaken. Afterwards, we added potassium iodide on the solution of iodine in water.
DATA & RESULTS A. Effect of temperature on solubility of a solid in water
SOLIDS Potassium Chloride Sodium Chloride
o
At 40 C -------
SOLUBILITY IN WATER At room temperature Soluble Soluble
At 80oC Soluble Insolube
B. Effect of the polarity of the solute and solvent SOLVENTS SOLUTE Potassium nitrate Sodium chloride Toluene Coconut Oil Copper sulfate
Water Soluble Soluble Immiscible Immiscible Soluble
Isopropyl AlcohoI Insoluble Insoluble Miscible Immiscible Insoluble
1:1 (V/V) water : isopropyl alcohol Insoluble Insoluble Immiscible Immiscible Insoluble
C. Influence of another substance
Iodine in water Iodine in water and Kl
SOLUBILITY Insoluble Soluble
According to the data shown above, the temperature greatly affects the solubility of the substances in water, just like Sodium chloride has shown. Also, the polarity serves as great influence on the solubility of the different samples shown above. It shows that if the solute and solvent is the same in polarity the more it will results to a greater solubility. The more the polarity is the same the more it will dissolve, but the more the polarity is NOT the same the more it will not be soluble. The influence of other substances can also affect the solubility of a solution. As the data is shown the iodine is insoluble in water, but as the potassium iodide was added the iodine can be soluble now. This experiment shows the n the solubility of the substances, it can be affect by many factors.
REFERENCE (1) http://www.wikipedia.com/solu http://www.wikipedia.com/solubility. bility. Retrieved: August 24, 2010 (2) Yuen C. 2003. Elements, Compound, and Mixture. (3) Clugston M. & Fleming R. (2000). P.108 (4) Figueroa, L. V. and Samonte, J.L. 2007. Laboratory Manual for General Chemistry. 3rd Ed. Manila: C & E Publishing, Inc. (5) Chang, R. Chemistry. 6 th ed. NY; WBC Mc Graw Hill, 1998 (6) Zayas, Clovia Isabel S. & Ramonesa, R. Ricardo. Laboratory Manual for General Chemistry. Manila: DLSU Press, 1994