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Mixing Acids and Bases

Mixing Acids and Bases. Is Dilution the Solution?. Some industries produce acidic wastes. Do acids become harmless as they are diluted? How much H 2 O is needed to neutralize an acid? What other choice do we have?. Recall…. In a neutral solution [H+] = [OH-] = 1.0 x 10 -7 mol/L

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Mixing Acids and Bases

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  1. Mixing Acids and Bases

  2. Is Dilution the Solution? • Some industries produce acidic wastes. Do acids become harmless as they are diluted? • Howmuch H2O is needed to neutralize an acid? • What other choice do we have?

  3. Recall… • In a neutral solution [H+] = [OH-] = 1.0 x 10-7 mol/L • the lower the pH, the more acidic the solution, [H+] > [OH-] • the higher the pH, the more basic the solution, [H+] < [OH-]

  4. Neutralization Equations ACID + BASE  WATER + SALT • Neutralization is a double displacement reaction which produces water and a soluble salt. • HBr (aq) + NaOH (aq) H2O (l) + NaBr (aq) http://www.chem.ox.ac.uk/vrchemistry/chapter16/Movies/Neutralization.swf

  5. Writing neutralization equations When acids and bases are mixed, a salt forms NaOH + HCl  H2O + NaCl base + acid  water + salt Question: Write the chemical reaction when lithium hydroxide is mixed with carbonic acid. Step 1: write out the reactants LiOH(aq) + H2CO3(aq) Step 2: determine products … LiOH(aq) + H2CO3(aq) Li2CO3(aq) + H2O(l) Step 3: balance the equation 2LiOH(aq)+H2CO3(aq)Li2CO3(aq)+2H2O(l) lithium hydroxide + carbonic acid  lithium carbonate + water Ca(OH)2 + H2SO4  2H2O + CaSO4

  6. http://www.saskschools.ca/curr_content/chem30/swf/neutralize.swfhttp://www.saskschools.ca/curr_content/chem30/swf/neutralize.swf

  7. Neutralization • Net Ionic Equation for Neutralization H+ + OH- HOH or H2O • When acids and bases ionize in water, the hydrogen ions (H+) and the hydroxide ions (OH-) are attracted to one another and combine to form water (HOH). • The salt produced from the reaction is soluble in water and therefore becomes the spectator ions.

  8. Neutralization • When a base is added to an acid, 1 mole of the OH- ions react with one mole of the H+ ions, decreasing the concentration of H+ ions. This causes the pH to increase to 7. • When an acid is added to a base, 1 mole of the H+ ions react with one mole of the OH- ions, decreasing the concentration of OH- ions. This causes the pOH increase and the pH to decrease to 7. • Neutralization destroys the properties of acids and bases.

  9. Titration • the progressive addition of an acid to a base, or vice versa, drop by drop from a burette, until the neutralization has occurred • Usually performed to analyse an unknown concentration of acid or base

  10. Some Vocab… • Titrant – a solution of known concentration (standard solution) dispensed from the burette. • Burette – a graduated glass tube with a valve at the bottom used for titrations • Pipette – a glass tube used for transferring small amounts of a solution very accurately

  11. When is a titration finished? • End point – the point at which the indicator changes colour during a titration • We select an indicator based on the the desired equivalence point. • Equivalence point – the point at which the number of moles of acid (H+ ions) added equals the number of moles of base (OH- ions) present or vice versa. n base= nacid

  12. Calculating Concentration • If the concentration of one of the solutions is known (standard solution), the concentration of the second solution can be calculated using stoichiometry. • http://web.fccj.org/~ksanchez/flash/Measurements/titration.swf titration demo

  13. Acid and Base Stoichiometry • A 35.00 mL sample of vinegar requires 51.74 mL of 0.4298 M sodium hydroxide to react with all of the acetic acid. What is the concentration of acetic acid (molarity) in the vinegar?

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