Earth Science II (Session 16) Solutions Earth Science II (Session 16) Ciencias de la Tierra II

Solutions and its components A solution is a homogenous mixture composed by a solute dissolved in a solvent. The solute is the least present component. The solvent is present in a larger size. For example, a spoon full of sugar dissolved in a glass of water forms a watery solution where the sugar is the solute and the water is the solvent or dissolvent. The name watery solution is given to every solution where water is the solvent. Ciencias de la Tierra II

Ciencias de la Tierra II . The solute and the solvent of a solution can exist as molecules or ions. For example, when sugar is dissolved in water, the sugar enters the solution in molecule form. When the sodium chloride is dissolved in water it is separated in chloride ions and sodium ions. In both cases the molecules and the solute ions are surrounded by the water molecules in the solution. Ciencias de la Tierra II

Solubility of Covalent Compounds Ciencias de la Tierra II

Ciencias de la Tierra II Solvatation process Ciencias de la Tierra II Burns, R. (1996)

Ciencias de la Tierra II Electrolytes A substance that breaks into ions when dissolved forms a solution known as electrolyte. When the substance is not ionized it is called non electrolyte. There are two types of electrolytes: Strong: when they are completely ionized. Weak: when they are partially ionized. Ciencias de la Tierra II

Factors that affect the solubility Properties of the solvent and solute: The ionic compounds are soluble in polar solvents, the covalent compounds are soluble in non polar solvents. “The similar dissolves the similar” Temperature: Gas solutions in a liquid, their solubility decreases with the increase in temperature. Solid solutions in a liquid generally increase their solubility when the temperature increases. Pressure: Solutions that contain solids and liquids are not affected by changes in pressure. The solubility of a gas in a liquid is directly proportionate to the partial pressure of a gas over a liquid. Ciencias de la Tierra II

Factors that affect the speed of dissolution Size of a particle: At less size of a particle in a solute greater the dissolution speed. Mixing speed: The speed of dissolution of a solute increases when mixed. Temperature: At higher temperature greater the dissolution speed. Ciencias de la Tierra II

Ciencias de la Tierra II Solution types Non saturated solutions: It is a solution where there is less solute then what can be dissolved at a given temperature. Saturated solution: It is a solution that has enough solute that can be dissolved at a given temperature. Oversaturated solution: It is an unstable solution that has more solute then what normally exists at a given temperature. If a crystallization process is created, all the solute excess is precipitated, living a saturated solution. Ciencias de la Tierra II

Ciencias de la Tierra II Solution types Brown, T. et al. (1991) Ciencias de la Tierra II

Ciencias de la Tierra II Bibliography Brown, T. et al. (1991) Chemistry: The Central Science. 5th ed. United States of America: Prentice Hall. Burns, R. (1996) Fundaments of Chemistry. 2nd. ed. United States of America: Prentice Hall. DiSpezio, M. et al. (1999) Science Insights: Exploring Earth and Space. 1st ed. United States of America: Prentice Hall. Ciencias de la Tierra II