PSC 4012 Ionic Phenomena: A study of an environmental problem

PSC 4012: Acid, Bases, Salts, Electrolytes, pH Heterogeneous mixture: Components can be distinguished Homogeneous mixture: Components cannot be distinguished Solutions are a type of homogeneous mixture. Examples of solutions:  Running water  Air Components:  Solute: The one who dissolves in the “solvent” (e.g. Coffee)  Solvent: The one in which the “solute” dissolves (e.g. Milk)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH Aqueous solutions: Solutions in which Water acts as the solvent  The polarity of Water makes it possible to dissolve ionic compounds (e.g. Salt) or molecules with a certain polarity  Non-polar substances (e.g. oil) do not dissolve well in Water.

PSC 4012: Acid, Bases, Salts, Electrolytes, pH Acids  Fruit juices, soft drinks, gastric juices  Sour taste  Red and blue litmus paper turn Red  Arrhenius: acids release H + when dissolved in Water (aqueous solution) HF (l) + H 2 O H + (aq) + F - (aq) H 2 SO 4 (l) + H 2 O 2H + (aq) + SO 4 2- (aq) HI (l) + H 2 O H + (aq) + I - (aq)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH

Bases  Cleaning products, some heartburn medication  Bitter taste  Feel slippery (react with oil in skin forming a kind of soap)  Red and blue litmus paper turn Blue  Arrhenius: bases release OH - when dissolved in Water (aqueous solution) NaOH (s) + H 2 O Na + (aq) +OH - (aq) Mg(OH) 2 (s) + H 2 O Mg 2+ (aq) + 2OH - (aq) NH 4 OH (l) + H 2 O NH 4 + (aq) + OH - (aq)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH

Salts  Table salt, Human diet (enhance food taste)  Made of a metal ion and a non-metal ion  Not all salts dissolve in water  Humans need salts (ions: Mg 2+, Ca 2+ ) for daily diet  Plats need salts (ions) that they get from the fertilizers  Red and blue litmus paper turn do not change colour  Arrhenius: salts release ions other than H + and OH - when dissolved in Water (aqueous solution) NaCl (s) + H 2 O Na + (aq) +Cl - (aq) CaCl 2 (s) + H 2 O Ca 2+ (aq) + 2Cl - (aq) AgNO 3 (s) + H 2 O Ag + (aq) + NO 3 - (aq)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH

Electrolytes: Substances that, when dissolved in water, allow an electrical current to flow through the solution, due to their separation into ions of different charges  Ionic compounds are good electrolytes  Salts, strong acids, and strong bases are good electrolytes, because they are ionic compounds Electrolytic solutions: Solutions that contain an electrolyte Nonelectrolytes: Substances that dissolve in water but do not separate into ions, therefore not incorporating charges into the solution, and as a consequence of that, not able to allow for electrical current to flow

PSC 4012: Acid, Bases, Salts, Electrolytes, pH Ionic dissolution (Electrolytes): Separation of a dissolved compound (Electrolyte) into two ions of opposite charge. NaCl (s) + H 2 O Na + (aq) + Cl - (aq) HCl (l) + H 2 O H + (aq) + Cl - (aq)  Physical change: No change of the nature of the solute.  The movement of the ions formed is what allows an electric current to flow. Molecular dissolution (Nonelectrolytes): Molecules do not produce ions when dissolved in water. C 12 H 22 O 11 (s) + H 2 O C 12 H 22 O 11 (aq)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH Strength of electrolytes: Degree to which the electrolyte dissolves into its ions. The higher the degree, the stronger the electrolyte. (Fig 4.8 on page 4.33) Strong electrolyte (Light bulb produces a bright light): NaOH (s) + H 2 O Na + (aq) + OH - (aq) 100 molecules 100 ions100 ions Weak electrolyte (Light bulb produces a dim light): CH 3 COOH (l) + H 2 O H + (aq) + CH 3 COO - (aq) 100 molecules 10 ions10 ions Nonelectrolyte (Light bulb does not light): C 12 H 22 O 11 (s ) + H 2 O C 12 H 22 O 11 (aq) 100 molecules

PSC 4012: Acid, Bases, Salts, Electrolytes, pH pH  Property that distinguishes acidic, basic and neutral solutions  Measures the concentration of H + ions in solution  Can be determined by indicator, pH paper, pH meter, etc.  pH scale: 0 – 14  pH < 7 (Acidic solution: Acids)  pH = 7 (Neutral solution: Salts)  pH > 7 (Basic solution: Bases)

PSC 4012: Acid, Bases, Salts, Electrolytes, pH pH pH = - log c(H + )  Log makes differences of one unit, to be ten times different (more or less)  Example: A (pH = 3), B (pH = 1), C (pH = 9)  Therefore B is 100 times more acidic than A

PSC 4012: Acid, Bases, Salts, Electrolytes, pH pH  pH scale: 0 – 14  pH < 7 (Acidic solution) _0 < pH < 3 (STRONGLY Acidic) _4 < pH < 6 (Slightly Acidic )  pH = 7 (NEUTRAL solution)  pH > 7 (Basic solution) _8 < pH < 11 (Slightly Basic) _12 < pH < 14 (STRONGLY Basic )

Acid-Base Equilibrium c(H + )pH = - log c(H + )Solution mol/L1Acid (H + ) mol/L2Acid (H + ) mol/L3Acid (H + ) mol/L4Acid (H + ) mol/L5Acid (H + ) mol/L6Acid (H + ) mol/L7Neutral (H 2 O) mol/L8Basic (OH - ) mol/L9Basic (OH - ) mol/L10Basic (OH - ) mol/L14Basic (OH - ) [H + ] = 10 -pH

Acid-Base Equilibrium Indicate True or False: __B (c(H + )=10 -2 M) has pH = 3 __A (c(H + )=10 -4 M) is 100 times more basic than B __C (neutral pH) is 1000 times more basic than D (c(H + )=10 -5 M) __D (c(H + )=10 -5 M) is a million times more acidic than E (pH = 10) Order these substances from most acidic to most basic: Order these substances from highest pH to lowest: F T F F B – A – D – C – E E – C – D – A – B

PSC 4012: Acid, Bases, Salts, Electrolytes, pH