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Strong vs Weak Acids 4-28-14

Strong vs Weak Acids 4-28-14. Strong acids ionize completely. HCl  H + + Cl - HNO 3  H + + NO 3 - H 2 SO 4  2H + + SO 4 -. Weak Acids ionize partially. H 2 CO 3  2H + + CO 3 - CH 3 COOH  H + + CH 3 COO - H 3 PO 4  3H + + PO 4 -.

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Strong vs Weak Acids 4-28-14

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  1. Strong vs Weak Acids 4-28-14

  2. Strong acids ionize completely HCl H+ + Cl- HNO3  H+ + NO3- H2SO4  2H+ + SO4-

  3. Weak Acids ionize partially H2CO3 2H+ + CO3- CH3COOH  H+ + CH3COO- H3PO4  3H+ + PO4-

  4. Ka is the acid dissociation constant • Large Ka value means more ionization, means stronger acid. • Smaller ka value means less ionization, means weaker acid.

  5. 1.Which acid is stronger? • Methanoic acid ka= 1.8 x 10-4 • Carbonic acid ka= 4.3 x 10-7

  6. 2.Which acid is weaker? • Ethanoic acid ka = 1.8 x 10-3 • Oxalic acid ka = 5.6 x 10-2

  7. https://www.youtube.com/watch?v=kdEh976I1YA

  8. Neutralization Reactions When an acid reacts with a base, the product is always a SALT and WATER. HCl + NaOH NaCl + H2O HNO3 + KOH  KNO3 + H2O CH3COOH + NaOH  NaCH3COO + H2O

  9. Write the reaction ratio under the equation Example: HCl + NaOH NaCl + H2O 1 mol 1 mol 1 mol 1 mol

  10. Your turn 3. H2SO4+ 2NaOH  Na2SO4 + 2 H2O 4. 2HCl + Ca(OH)2  CaCl2 + 2 H2O

  11. Titration • to find concentration of an unknown acid or base • Use the balanced equation to set up a mole ratio • Use the volume of titrant to calculate concentration of unknown

  12. Titration: strong acid with strong base

  13. Titrating weak acid with strong base

  14. Comparing strong acid vs weak acid titration with strong base

  15. How does a titration work? 1. A measured volume of an acid solution of unknown concentration is added to a flask 2. Several drops of indicator are added to the solution while the flask is gently swirled 3. Measured volumes of a base of known concentration (standard solution) are added until the indicator just barely changes color. 4. Neutralization occurs at the equivalence point = end point of the titration (color change)

  16. Calculations A 25ml of H2SO4 is neutralized by 18ml of 1.0M NaOH. What is the concentration of the H2SO4 solution? H2 SO4 + 2 NaOH Na2 SO4 + 2H2O Known: Stoich: Final equation: Molarity = mol / L

  17. https://www.youtube.com/watch?v=SBHGaY3kA4U

  18. How to • Convert ml to L (divide by 1000) • Find moles of base (moles = M x L) • Use balanced equation to set up mole ratio (place unknown at the top) • Multiply answer from 2. (moles) with the ratio from 3. (mole ratio) • Find concentration of acid M =moles L (answer of 4. divided by L of acid from 1.)

  19. Practice A 50 ml of H2SO4 is neutralized by 25ml of 1.0M NaOH. What is the concentration of the H2SO4 solution? H2 SO4 + 2 NaOH Na2 SO4 + 2H2O

  20. Practice/exit slip A 25ml of H2SO4 is neutralized by 50ml of 1.0M NaOH. What is the concentration of the H2SO4 solution? H2 SO4 + 2 NaOH Na2 SO4 + 2H2O

  21. Bellwork 25ml of HCl are titrated with 30 ml of 0.5M NaOH. What is the concentration of the acid. HCl + NaOH NaCl + H2O

  22. Work due by end of class today: Lab report with completed calculations Vocab foldable

  23. Put on your goggles andSet up your burettesTitration strong acid with strong base • Fill burette with NaOH solution. Record your starting volume . • Measure 20 ml of HCl into a small Erlenmeyer flask (using a measuring cylinder) • Add 5 drops of Bromothymol blue indicator. • Swirl flask gently as you add NaOH from the burette to the flask until you get a slight color change to green/blue • Record volume used from the burette Work in groups of 3

  24. Average

  25. Calculate the molarity (M) of the acid (HCl) HCl + NaOH NaCl + H2O ___ml ____ml ? M 0.1M

  26. Vocab foldable (grade for color/quality/completeness) Equivalence point End point Titration Weak acid Strong acid Base Alkaline Buffer Indicator Phenolphtalein Bromothymol blue Neutralization Molarity Standard solution

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