Chemical Reactions: Aqueous Solutions Mr. Bennett November, 2009 Adapted from J. Speck (2008) and A. Allen, 2008

Solution Solution- A homogeneous mixture of two or more substances, in which one is generally considered the solvent and the other the solute. Solution- A homogeneous mixture of two or more substances, in which one is generally considered the solvent and the other the solute. Solvent- Medium in which another substance is dissolved. Solvent- Medium in which another substance is dissolved. Solute- the substance which is dissolved. Solute- the substance which is dissolved.

Classification of Matter Solutions are homogeneous mixtures

Aqueous solution Aqueous Solution- a solution that is made using water as the solvent. Aqueous Solution- a solution that is made using water as the solvent. The water you drink every day contains small concentrations of many ions, which result from the dissolving of solid materials in the environment. Many of these are necessary ingredients in our diet. The water you drink every day contains small concentrations of many ions, which result from the dissolving of solid materials in the environment. Many of these are necessary ingredients in our diet.

Aqueous Solutions Dissolving an ionic solid involves separating each ion from the oppositely charged ions that surround it in the solid state. Dissolving an ionic solid involves separating each ion from the oppositely charged ions that surround it in the solid state. Water is very good at this because each water molecule has a positively and negatively charged end. Water is very good at this because each water molecule has a positively and negatively charged end.

Structure of water

Electrolytes Electrolytes- compounds whose aqueous solutions conduct electricity. Electrolytes- compounds whose aqueous solutions conduct electricity. When we dissolve compounds in water we can test to see if they break down into ion or not by seeing if a charge will pass through it. When we dissolve compounds in water we can test to see if they break down into ion or not by seeing if a charge will pass through it.

Types of Electrolytes Electrolytes can be classified as strong or weak. Electrolytes can be classified as strong or weak. A strong electrolyte will dissolve completely like NaCl. A strong electrolyte will dissolve completely like NaCl. NaCl (aq) ≡ Na + (aq) + Cl - (aq) NaCl (aq) ≡ Na + (aq) + Cl - (aq) 100% Dissociation = strong electrolyte 100% Dissociation = strong electrolyte Because ions are highly concentrated in the solution, the solution is a good conductor of electricity and is a strong electrolyte

Types of Electrolytes Other substances produce only a small concentration of ions when they dissolve, and so they are poor conductors of electricity. These are called weak electrolytes. Other substances produce only a small concentration of ions when they dissolve, and so they are poor conductors of electricity. These are called weak electrolytes. Ex: acetic acid dissolves in water, only a small percent of the molecules are ionized to produce cations and anions. Thus it does not conduct electricity very well and is a weak electrolyte. Ex: acetic acid dissolves in water, only a small percent of the molecules are ionized to produce cations and anions. Thus it does not conduct electricity very well and is a weak electrolyte.

Types of Electrolytes Nonelectrolytes- substances that dissolve in water but do not ionize. Thus they do not conduct electricity. Nonelectrolytes- substances that dissolve in water but do not ionize. Thus they do not conduct electricity. These consist of molecular or covalent compounds like sugar, ethanol, and antifreeze. These consist of molecular or covalent compounds like sugar, ethanol, and antifreeze.

Solubility of Ionic Compounds Not all ionic compounds dissolve in water. Many dissolve only to a small extent and other are insoluble. Not all ionic compounds dissolve in water. Many dissolve only to a small extent and other are insoluble. There are rules about which types of ionic compounds are water soluble. There are rules about which types of ionic compounds are water soluble. You will receive a hand out explaining the rules. You will receive a hand out explaining the rules.