Temperature and solubility

Instituto Cumbres

Solubility and Temperature
Practice 2
Andrés Ventre Santandreu

1st Semester

Teacher:
Miss. Martha Michelis

Villahermosa, Tabasco, México September, 2011

Objectives
1. Learn how solvation acts.
2. Identify how the solvent and solute interact in a solution.
3. Learn how temperature affects the capacity of solute in a solution.Introduction

SOLUBILITY is an ability of a substance to dissolve. In the process of dissolving, the substance which is being dissolved is called a solute and the substance in which the solute is dissolved is called a solvent. A mixture of solute and solvent is called a solution.

SOLUBILITY is understood as a maximum amount of solute that dissolves in a solvent also called equilibrium. Inchemistry equilibrium is a state where reactants and products reach a balance - no more solute can be dissolved in the solvent in the set conditions (temperature, pressure). Such a solution is called a saturated solution.
Some substances, like water and alcohol, can be mixed together and create a homogenous phase in any proportion. A solubility measure cannot be applied to such two substances. Suchsubstances are called miscible. On the other hand if two substances cannot be mixed together (like water and oil), they are called immiscible.
Many physical properties of materials including the phase (solid, liquid, gaseous or plasma), density, solubility, vapor pressure, and electrical conductivity depend on the temperature. Temperature also plays an important role in determining the rate andextent to which chemical reactions occur. This is one reason why the human body has several elaborate mechanisms for maintaining the temperature at 310 K, since temperatures only a few degrees higher can result in harmful reactions with serious consequences. Temperature also controls the thermal radiation emitted from a surface. One application of this effect is the incandescent light bulb, inwhich a tungsten filament is electrically heated to a temperature at which significant quantities of visible light are emitted.
The solubility of a given solute in a given solvent typically depends on temperature. For many solids dissolved in liquid water, the solubility increases with temperature up to 100 °C. In liquid water at high temperatures, the solubility of ionic solutes tends to decreasedue to the change of properties and structure of liquid water; the lower dielectric constant results in a less polar solvent.
Gaseous solutes exhibit more complex behavior with temperature. The temperature is raised, gases usually become less soluble in water (to minimum which is below 120 °C for most permanent gases), but more soluble in organic solvents.
Materials

* 5 beakers
* 1thermometer
* 1 burner
* 1 balance
* 500 g Sucrose (sugar)
* NaOH or Ca(OH)2
* Water
* Ice cubes
* Retord stand with ring

Procedure

1) Measure 20 ml of water in a beaker. The temperature of water should be the lowest temperature as possible (use only melted ice cubes). Add the amount of sucrose needed to obtain a solution (you should measure the amounts added).Register the temperature and the mass of sugar used.
2) Measure 20 ml of water in the second beaker. The temperature of the water should be 10°C higher than the first one; add enough sucrose to obtain a solution. Register the temperature of the water and the mass of sucrose.
3) Measure 20 ml of water in a beaker. Heat it until it raises 40°C. Add enough sucrose to obtain a solution. Registerthe temperature of the water and the mass of sucrose.
4) Measure 20 ml of water in a beaker. Heat it until it rises 70°C. Add enough sucrose to obtain a solution. Register the temperature of the water and the mass of sucrose.
Exothermic solvatation (or solvation or heat of dissolution)
1) Measure 20 ml of water in a beaker. Register the temperature.
2) Measure 10 g of NaOH or...