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PROPERTIES OF A SOLUTION. Solutions are homogeneous mixtures composed of at least 1 solute and 1 solvent. Both solute and solvents may be gases, liquids or solids. Example: metal alloys are used in solid form but are dissolved in the liquid form.
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Solutions are homogeneous mixtures composed of at least 1 solute and 1 solvent. Both solute and solvents may be gases, liquids or solids. Example: metal alloys are used in solid form but are dissolved in the liquid form. Electrolytes are soluble compounds whose aqueous solutions conduct electricity. Non electrolytes are soluble compounds whose aqueous solutions don’t conduct electricity. A positive test for an electrolyte is when an ohmmeter’s needle moves. In solution, they exist in the form of ions. In electrolyte solutions the total positive charge = the total negative charge. Strong electrolytes readily change into ions and weak electrolytes don’t change as quickly.
Ionic solutions contain at least one metal element and 1 non-metal element. Non ionic solutions contain no metal elements. When ionic solutions dissolve they are 100% dissociated into ions therefore are strong electrolytes. Acids, Bases and Salts Instead of learning the properties and behaviors of each chemical substance individually, it is easier to collect them into groups and to study the similar properties of the whole group. When this idea is applied to inorganic compounds three main groups emerge: acids, bases, and salts.
General Definitions of Acids & Bases Arrhenius Definition of Acids & Bases (1887) • oldest, traditional definition • it is based on his study of electrolytes (substances whose water solution conducts an electric current) • He defined acids & bases on the basis of the ions he thought were formed when acids & bases dissolved in water. Arrhenius Base • a substance which ionizes to produce hydroxide ions (OH-) in water solution • E.g. NaOHNa+ + OH- • E.g. Mg(OH)2Mg2+ + 2OH-
Arrhenius Acid • a substance which ionizes in water to produce hydrogen ions (H+, protons) • e.g. HClH+ + Cl- • e.g. HNO3H+ + NO3- B. Bronsted-Lowry Definition of Acids & Bases • more modern definition (1923) • gives a broader, more general definition of acids & bases • corrects the Arrhenius view that H+ ions can exist by themselves in solution
Bronsted-Lowry Acid • a substance which donates a proton(H+) in a chemical reaction • E.g. reaction of HCl(g) dissolving in water HCl(g) + H2O H3O+ + Cl- Overall, the HCl acts as a proton donor, or acid: it donates or gives an H+ ion away. Bronsted-Lowry Base • a substance which accepts a proton during a chemical reaction e.g. NH3 + H2O NH4+ + OH- E.g. S2- + HOH SH- + OH-