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Acids and Bases

Learn the properties of acids, bases, and salts, including their conductivity, reactions, taste, pH levels, and common examples. Compare the Arrhenius and Bronsted-Lowry theories, understand the meaning of pH, and explore neutralization reactions and acid-base titration.

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Acids and Bases

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  1. Acids and Bases

  2. Properties of Acids • In aqueous solutions, they conduct electricity They are ______________ • Metals above H2 on Table J will react with acids to produce hydrogen gas and a salt • Will Mg react with HCl? _________ • Will Cu react with HCl? _________ • Acids cause color changes in acid-base indicators • Acids react with bases to form a salt + H2O _________ • sour taste • pH levels __________ • Common examples:___________________________ • Table K

  3. Properties of Bases • In aqueous solutions, bases conduct electricity  They are also ______________ • Bases cause color changes in acid-base indicators. • Bases react with acids to form a salt + H2O!! ____________________________ • bitter taste • pH levels ___________ • Common examples: ____________________ • Table L

  4. Properties of Salts • Like acids and bases, salts are also _________________ • Salts are formed as a product of neutralization reactions • Neutral  most have a pH of _______ • Salts are ionic compounds • ( _______+ _______) • Examples:

  5. The Arrhenius Theory • Svante Arrhenius • Based his ideas on the fact that aqueous solutions of acids and bases are electrolytes • said that the propertiesofacids and bases are because of their H+ and OH- ions

  6. Arrhenius Acids • An acid is a substance that has H and releases (yields) H+ ions as the only positive ions in solution • Adding an acid to an aqueous solution ___________ the concentration of H+ ions in the solution • The H+ ions attach to H2O, forming hydronium ions _________ • Examples: ___________________ • Can be monoprotic or diprotic________

  7. Arrhenius Bases • A base is a substance that has OH and releases (yields) OH- ions as the only negative ions in an aqueous solution • Adding a base to an aqueous solution __________ the concentration of OH- ions in the solution • Examples: __________________

  8. The Bronsted-Lowry Theory • Arrhenius’ theory had some limitations, so they expanded the definitions of acids and bases • An acid is an H+donor • A base is an H+acceptor • H+ is simply a proton which interacts strongly with nonbonding e- on the oxygen of a water molecule • Interaction results in a hydronium ion H3O+

  9. Bronsted-Lowry • Acids and bases can be defined in terms of ability to donate protons • Acid: proton donor • Base: proton acceptor

  10. Bronsted- Lowry EXAMPLE HCl(g) + H2O(l) H3O+(aq) + Cl-(aq) HCl: _______ H2O: _______

  11. Comparing the two theories NH3(aq) + H2O(l)  NH4+(aq) + OH- (aq) • According to Arrhenius, NH3 is a base because adding it to water increases the hydroxide ion concentration • Bronsted-Lowry classifies it as a base because it accepts a proton from H2O, and the water acts as an acid because it donates a proton

  12. Amphoteric Substances • Substances that can act as an acid or base • Ex: H2O • With ammonia it’s an acid • With HCl it’s a base

  13. The Meaning of pH • pH measures the H+ ion concentration in a solution. If….. • [H+] = [OH-] ______________________ • [H+] > [OH-] ______________________ • [H+] < [OH-] ______________________ • An increasing pH means the H+ ion concentration is _________ • A decreasing pH means the H+ ion concentration is _________ • The pH scale is logarithmic • Each change of a single pH unit signifies a TENFOLD change in the concentration of H+ ions • A solution with a pH of 4 is 10x more acidic than a pH of ___ • A solution with a pH of 7 is 100x more acidic than a pH of __

  14. Calculations with pH Examples: Determine the pH given the [H+] concentration 1. If [H+] = 1 x 10-4 pH = ___________ 2. If [H+] = 1 x 10-11 pH = ___________ 3. If [H+] = 1 x 10-7 pH = ___________ 4. What is the pH of a 0.00001M HCl solution? _________ 5. What is the pH of a 0.000000001M solution? _________ 6. What is the pH of a 0.0001M solution? _________

  15. Neutralization Reactions • When an acid reacts with a base to produce salt and water • It occurs when there are the same amount of H+ ions as OH- ions • General formula: acid + base  water + salt

  16. Writing Neutralization Reactions • Take the H+ from the acid and the OH- from the base and combine them to form H2O • Then combine the other ions to form the salt • Remember to look at oxidation numbers!!!! • Make sure the equation is balanced • When a solution is neutral, the moles of H+ = moles OH- • Ex: HCl + KOH  ___________________ • Ex: H2SO4 + NaOH  ___________________

  17. Acid-Base Titration • A laboratory technique used to achieve neutralization between an acid and a base • It is used to find the unknownmolarity of an acid or a base by slowly adding measured volumes of an acid or base of knownmolarity until neutralization occurs • End point: The point when the indicator changes color • nHMAVA = nOHMBVB

  18. Examples • How many milliliters of 4.00M NaOH are required to exactly neutralize 50.0mL of a 2.00M solution of HNO3? • If it takes 55mL of 0.1M NaOH solution to neutralize 450mL of an H2SO4 solution of unknown concentration, what’s the molarity of the acid?

  19. Table M Examples • You put bromcresol green • in a solution  it turns blue Then you put bromthymol • blue in the same solution  it turns yellow What is the pH of the solution? _____________ Is the solution acidic or basic? _____________ • A solution turns yellow with thymol blue and blue with bromthymol blue. What is the pH of th\e solution? ____________ Is the solution acidic or basic? ____________

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