UNIT 11 ACIDS, BASES & SALTS Ch. 8

8.1 ACIDS, BASES & Ph   ACIDS Acids refer to any compound that increases the number of hydronium ions when dissolved in water. A hydronium ion is a water molecule with a hydrogen ion attached to it. H3O+. All acids ionize when dissolved in water Charged ions able to move about in the water

Ex. Nitric Acid, HNO3   HNO3 + H2O → H3O+ + NO3 - (Nitric acid + water yields hydronium ions + nitrate ions) Acids that ionize completely in water are called strong acids Examples of strong acids Nitric acid, HNO3 Hydrochloric acid, HCl Sulfuric acid, H2SO4

Acids that do not completely ionize in water are called weak acids Examples of weak acids Acetic acid, CH3COOH - vinegar Citric acid, H3C6H5O7 Formic acid, HCOOH, acid in stinging ants  

Other Characteristics of Acids Taste sour Conduct electricity   Substances that dissolve in water such that the solution conducts electricity are called electrolytes. Strong acids are strong electrolytes. Weak acids are weak electrolytes. Warning: Weak acids can damage the skin if it is in a concentrated form.

BASES   A base is any compound that increases the number of hydroxide ions (OH-) when dissolved in water. Some bases contain OH, Some do not Those that do not, react with H2O to produce OH- ions. Strong bases are those that contain a metal ion and an OH. These are also called metal hydroxides.

Examples of weak bases Ammonia, NH3 Example of strong bases: Potassium hydroxide, KOH Sodium hydroxide, NaOH Calcium hydroxide, Ca(OH)2 Examples of weak bases Ammonia, NH3 Ammonia, NH3 is a base that does not have OH. NH3 + H2O → NH4 + + OH- Water acts as an acid. Gives an H to ammonia to form ammonium (NH4-) ion.

  Bases attack living tissue rapidly. Some acids are more dangerous than acids, particularly KOH and NaOH.

Measuring Acidity & Alkalinity pH pH is a value to express the acidity or alkalinity of a solution. Tells us how acidic or basic a solution is. A measure of the amount of H3O+ ions but also indictates the OH- concentration.

Ranges from 0 to 14 Neutral solutions have pH of 7. For neutral solutions, the concentration of H3O+ is equal to the concentration of OH- Pure (distitlled) water is a neutral solution pH < 7 are acidic pH > 7 are basic Acidic solutions: H3O+ ions > OH- ions Basic solutions: OH- ions > H3O+ ions

Litmus Paper Litmus is a paper coated with an indicator that changes color depending on the pH of the solution. Bases turn red litmus paper blue. Acids turn blue litmus paper red   Another method to test to determine whether a substance is an acid or a base is litmus paper.

Molarity of solutions Molarity(M) refers to the concentration of a solution. Expressed in moles/Liter Molarity of pure water has a H3O+ concentration of .0000001 moles/L or 10-7 moles/L . Its pH is 7. pH is simply the negative power of 10 of H3O+ ions. Apple juice has a H3O+ concentration of 10-3 M. Therefore, its pH is 3.(The negative of -3)

Small changes in pH mean large differences in H3O+ concentration. Each whole pH difference results in a 10 fold difference in H3O+ concentration Coffee has a pH of 5. Apple juice has a pH of 3. The acidity of apple juice is 100 times stronger. Difference between 10-5 and 10-3 is 102 or 100

ASSIGMENT FOR NEXT TIME WORK ON 8.1 IN ACIDS/BASES PACKET

8.2 REACTIONS OF ACIDS & BASES   Remember: Strong acids ionize completely in water (The break down completely) HCl + H2O → H3O+ + Cl- Remember: Strong bases ionize completely in water as well. NaOH + H2O → Na+ + OH- + H2O

If HCl and NaOH are mixed (= concentration and amount), Chemical equation can be written 2 ways: HCl(aq) + NaOH(aq) → NaCl + H2O or H3O+ + Cl- + Na+ + OH- → Na+ + Cl - + 2H2O The Na+ and Cl - ions are often called spectator ions because they do not change during the reaction.

Another example Sulfuric acid, H2SO4 + Potassium hydroxide, KOH H3O+ + SO4- + K+ + OH- → K+ + SO4- + 2H2O What are the spectator ions in this reaction?

2 things commonly form when an acid and a base are mixed together: water and a salt A salt is an ionic compound that forms from the reaction between an acid and a base. Salts are often soluble in water. Salts commonly are made with a metal ion. Water forms from the H+ and OH- ions and the salt forms from the other ions. The reaction between an acid and a base is called a neutralization reaction.

Common Salts Use Aluminum sulfate (Al2(SO4)3 In antiperspirants   Aluminum sulfate (Al2(SO4)3 In antiperspirants Calcium chloride (CaCl2) De-icer on roads Potassium chloride (KCl) Table salt substitute Sodium carbonate (Na2CO3) Water softener Sodium hydrogen carbonate (NaHCO3) Baking powder. Upset stomachs

The final pH in a neutralization reaction depends on: The concentration of the acid The concentration of the base Whether the acid and/or base are strong or weak.   Ex: The product from a strong acid (HCl) + a weak base (ammonia) will still be an acid, although a weaker acid with a little higher pH. Ex: The product from a strong acid + an equally strong base will be water and a salt. pH will be 7.0

ASSIGNMENT COMPLETE 8.2 ASSIGNMENT ON BACK OF 8.2 NOTES WORK ON TEST REVIEW DUE TOMORROW