Solutions, acids, baese and pH

Heterogeneous Mixtures

• The amount of each substance in different samples of a heterogeneous mixture varies.
• Example: Any two shovelfuls of dirt from a garden would not be exactly the same.
• A suspension is a mixture in which large particles of a material are more or less evenly dispersed throughout a liquid or gas.
• Example: natural orange juice, which contains particles of pulp.
• Particles in a suspension may settle over time, and may be filtered out.
• Liquids that do not mix with each other are immiscible. Miscible liquids mix to form solutions.
• A colloid is a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions and that are suspended in a liquid, solid or gas.
• Particles in a colloid are too small to settle out.
• However, particles in a colloid are large enough to scatter light that passes through: this is called the Tyndall effect.
• An emulsion is any mixture of two or more immiscible liquids in which one liquid is dispersed
  in the other.

Homogeneous Mixtures

• Homogeneous mixtures not only look uniform, but
  are uniform.
• Example: salt water, which looks uniform even when you examine it under a microscope

A solution is a homogeneous mixture of two or more substances uniformly dispersed throughout.

• Many different substances can dissolve in water.
  For this reason, water is sometimes called the universal solvent.
• Water can dissolve ionic compounds because of its structure: it is a polar compound, which is a molecule that has an uneven distribution of electrons.
• Because they are polar, water molecules attract both the positive and negative ions of
  an ionic compound.

What is pH?

• pH is a value used to express the acidity or basicity of a solution.
• pH values correspond to the concentration of hydronium ions. They also indicate hydroxide ion concentration.
• A neutral solution, such as pure water, has a
  pH of 7.
• An acidic solution has a pH of less than 7.
• A basic solution has a pH of greater than 7.
• An acid is a compound that dissolves in water to increase the number of hydronium ions, H 3O +,
  in solution.
• Some examples of strong acids:
• Hydrochloric acid, HCl
• present in your stomach
• Sulfuric acid, H 2SO 4
• car batteries; the most-used industrial chemical
• Nitric acid, HNO 3
• used in manufacturing fertilizers and explosives
• Some examples of weak acids:
• Acetic acid, CH 3COOH
• the acid in vinegar
• Formic acid, HCOOH
• the acid in stinging ants
• Citric acid, H 3C 6H 5O 7
• the acid in citrus fruits
• A base is a compound that dissolves in water to increase the number of hydroxide ions, OH –,
  in solution.
• Strong bases are ionic compounds that contain a metal ion and a hydroxide ion, for example, NaOH, sodium hydroxide.
• Weak bases, such as ammonia, NH 3, ionize incompletely in water to form hydroxide ions.