Lecture 6: Gases and Solutions Chemistry - SPRING 2017 Course lecturer : Jasmin Šutković 29th March 2017

Contents Properties of gases Pressure and Volume International University of Sarajevo Properties of gases Pressure and Volume Temperature and Volume Temperature and Pressure Combined Gas laws Volume and Moles Partial pressure law Solutions Electrolytes and Non-electrolytes Solubility Concentrations of Solutions Dilution of Solutions Properties of Solutions Osmosis

Properties of gases H2, N2, O2, F2, Cl2 and the noble gases. Another group of gases includes the oxides of the nonmetals on the upper right corner of the periodic table, such as CO, CO2, NO, NO2, SO2, and SO3 Properties: Gas particles are far apart, whereas particles of both liquids and solids are held close together. A gas has no definite shape or volume and will completely fill any container. Because, there are great distances between gas particles, a gas is less dense than a solid or liquid, and easy to compress.

Kinetic properties of gases 1. A gas consists of small particles atoms or molecules that move randomly with high velocities. 2. The attractive forces between the particles of a gas are usually very small. 3. The actual volume occupied by gas molecules is extremely small compared with the volume that the gas occupies. 4. Gas particles are in constant motion, moving rapidly in straight paths. 5. The average kinetic energy of gas molecules is proportional to the Kelvin temperature.

The gas particles in the air, mostly oxygen and nitrogen, exert a pressure on us called atmospheric pressure

Units of pressure

Boyls Law Pressure and Volume are inversely related. The Volume changes along with the pressure (with no change in T and n)

Problem

Charles’s Law In 1787, Jacques Charles, a balloonist as well as a physicist, proposed that the volume of a gas is related to the temperature. This became Charles’s law, which states that the volume (V) of a gas is directly related to the temperature (T) when there is no change in the pressure (P) or amount (n) of gas

Illustration

Problem

Gay-Lussac’s Law If we maintain a constant volume and amount of gas, the pressure will increase. The volume remain constant. In Gay Lussacs law the pressure of a gas is directly related to its Kelvin temperature.

llustration

Problem

Combined law

Problem

Avogadro’s Law

Vn= 22.4L x mol-1 V= n x Vn

Problem V = n x Vn V=2 mol x 22.4L/mol V= 44.8 L

Daltons law Many gas samples are a mixture of gases. For example, the air you breathe is a mixture of mostly oxygen and nitrogen gases. Therefore, the total pressure of the gases in a mixture is a result of the collisions of the gas particles regardless of what type of gas they are.

Summary

Introduction to Solution Solutions are everywhere around us. Most of the gases, liquids, and solids we see are mixtures of at least one substance dissolved in another. There are different types of solutions. Air (oxygem, nitrogen, other gases) Carbon dioxide gas dissolved in water makes carbonated drinks. Coffee or tea, we use hot water to dissolve substances from coffee beans or tea leaves.

Introduction to Solution Solutions can be described by their concentration, which is the amount of solute in a specific amount of that solution. Solutions are also diluted by adding a specific amount of solvent to a solution.

Solutions A solution is a homogeneous mixture in which one substance, called the solute, is uniformly dispersed in another substance called the solvent.

Types of Solutes and Solvents Solutes and solvents may be solids, liquids, or gases

Solvent - Water

Water in our body Every day you lose between 1500 and 3000 mL of water from the kidneys as urine, from the skin as perspiration, from the lungs as you exhale, and from the gastrointestinal tract

Formation of Solutions Energy is needed to start the interaction of solutes and solutions. Attraction must occur and it will happen if solution and solutes have similar polarity! The expression “like dissolves like” is a way of saying that the polarities of a solute and a solvent must be similar in order for a solution to form.

Solutions with Nonpolar Solutes Compounds containing nonpolar molecules, such as iodine (I2) or oil do not dissolve in water because there are essentially no attractions between the particles of a nonpolar solute and the polar solvent. Nonpolar solutes require nonpolar solvents for a solution to form.

Electrolytes and Nonelectrolytes Solutes can be classified by their ability to conduct an electrical current. When electrolytes dissolve in water, the process of dissociation separates them into ions forming solutions that conduct electricity. When nonelectrolytes dissolve in water, they do not separate into ions and their solutions do not conduct electricity.

Types of Electrolytes Strong electrolytes - 100% dissociation of the solute into ions. Exp: Mg(NO3)2 Weak electrolytes- partial dissociation of the solutes into ions .Exp : HF

Electrolytes in the body play an important role in maintaining the proper function of the cells and organs in the body. Typically, the electrolytes sodium, potassium, chloride, and bicarbonate are measured in a blood Test.

Solubility The term solubility is used to describe the amount of a solute that can dissolve in a given amount of solvent. Many factors, such as the type of solute, the type of solvent, and the temperature, affect the solubility of a solute. Solubility, usually expressed in grams of solute in 100 g of solvent, is the maximum amount of solute that can be dissolved at a certain temperature.

Types of solutions If a solute readily dissolves when added to the solvent, the solution does not contain the maximum amount of solute. We call this solution an unsaturated solution. A solution that contains all the solute that can dissolve is a saturated solution. When a solution is saturated, the rate at which the solute dissolves becomes equal to the rate at which solid forms, a process known as recrystallization.

Saturation problems High level of Uric acid High level of Calcium

Concentration of Solutions The amount of solute dissolved in a certain amount of solution is called the concentration of the solution. The amount of a solute may be expressed in units of grams, milliliters, or moles. The amount of a solution may be expressed in units of grams, milliliters, or liters. c= n/V

Mass percentage

Volume percent

Molarity of Solutions

Conversion factors

Dilution of Solutions In chemistry and biology, we often prepare diluted solutions from more concentrated solutions. In a process called dilution, a solvent, usually water, is added to a solution, which increases the volume.

Equation

Types of mixtures

Properties of mixtures

Osmosis – Osmotic pressure The movement of water into and out of the cells of plants as well as the cells of our bodies is an important biological process In a process called osmosis, water molecules move through a semipermeable membrane from the solution with the lower concentration of solute into a solution with the higher solute concentration.

Hemodialysis If the kidneys fail to dialyze waste products, increased levels of urea can become life-threatening in a relatively short time. A person with kidney failure must use an artificial kidney, which cleanses the blood by hemodialysis.