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Mixing Acids and Bases

Mixing Acids and Bases. When acids and bases are mixed, a salt forms NaOH + HCl  H 2 O + NaCl base + acid  water + salt . Writing neutralization equations. Ca(OH) 2 + H 2 SO 4  2H 2 O + CaSO 4.

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Mixing Acids and Bases

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  1. Mixing Acids and Bases

  2. When acids and bases are mixed, a salt forms NaOH + HCl  H2O + NaCl base + acid  water + salt Writing neutralization equations Ca(OH)2 + H2SO4  2H2O + CaSO4 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 … H2O and Li2(CO3) 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

  3. Assignment Write balanced chemical equations for these neutralization reactions. Under each compound give the correct IUPAC name. • iron(II) hydroxide + phosphoric acid • Ba(OH)2(aq) + HCl(aq) • calcium hydroxide + nitric acid • Al(OH)3(aq) + H2SO4(aq) • ammonium hydroxide + hydrosulfuric acid • KOH(aq) + HClO2(aq)

  4. a) 3Fe(OH)2(aq) + 2H3PO4(aq)  Fe3(PO4)2(aq) + 6H2O(l) iron(II) hydroxide + phosphoric acid  iron (II) phosphate b) Ba(OH)2(aq) + 2HCl(aq) BaCl2 (aq) + 2H2O(l) barium hydroxide + hydrochloric acid  barium chloride c) Ca(OH)2(aq) + 2HNO3(aq)  Ca(NO3)2(aq) + 2H2O(l)calcium hydroxide + nitric acid  calcium nitrate d) 2Al(OH)3(aq) + 3H2SO4(aq) Al2(SO4)3(aq) + 6H2O(l)aluminum hydroxide + sulfuric acid  aluminum sulfate e) 2NH4OH(aq) + H2S(aq) (NH4)2S(aq) + 2H2O(l)ammonium hydroxide+ hydrosulfuric acid ammonium sulfide f) KOH(aq) + HClO2(aq) KClO2(aq) + H2O(l) potassium hydroxide + chlorous acid  potassium chlorite

  5. Calculations involving Neutralization Reactions

  6. Sample Problem 1What volume of 0.250M sulfuric acid, H2SO4 (aq) is needed to react completely with 37.2 mL of 0.650 M potassium hydroxide, KOH (aq)? • Step 1. Write a balanced equation for the reaction. H2SO4(aq) + 2KOH(aq) 2H20(l) + K2SO4(aq)

  7. H2SO4(aq) + 2KOH(aq)  2H20(l) + K2SO4 (aq) Step 2. Using the information provided, calculate the number of moles of base. c = .650 mol/L V= 37.2 mL = 0.0372 L n = cV = (.65 mol/L)(0.0372L) = 0.02418 mol

  8. H2SO4(aq) + 2KOH(aq)  2H20(l) + K2SO4 (aq) Step 3. Determine the number of moles of H2SO4 needed to neutralize the lithium hydroxide. (Use mole ratio, if necessary) =0.02418mol KOH X 1 mol H2SO4 2 mol KOH =0.01209 mol H2SO4

  9. H2SO4(aq) + 2KOH(aq)  2H20(l) + K2SO4 (aq) Step 4. Find the volume of H2SO4(aq) based on the moles and concentration of H2SO4 solution. c= n/V V= n/c = 0.01209 mol/0.250M = 0.0484 L = 48.4 mL

  10. Problem 2: A 25.0 mL sample of hydrochloric acid is titrated with 1.00 mol/L NaOH. The end point is reached when 67.5 mL of base has been added. Calculate the concentration of the acid in mol/L. • Step 1. Write a balanced equation for the reaction. HCl(aq) + NaOH(aq)  H20(l) + NaCl(aq)

  11. HCl(aq) + NaOH(aq)  H20(l) + NaCl(aq) Step 2. Using the information provided, calculate the number of moles of base. c = 1.00 mol/L V= 67.5 mL = 0.0675 L n = cV = (1.00 mol/L)(0.0675L) = 0.0675 mol

  12. HCl(aq) + NaOH(aq)  H20(l) + NaCl(aq) Step 3. Determine the number of moles of HCl needed to neutralize the sodium hydroxide. (Use mole ratio, if necessary) In this case nA= nB = 0.0675 mol

  13. HCl(aq) + NaOH(aq)  H20(l) + NaCl(aq) Step 4. Find the concentration of HCl(aq) based on the moles and volume of HCl solution. c= n/V = 0.0675 mol/0.0250L = 2.70 mol/L

  14. Calculate the % of HCl (as m/m) in the solution, given that its density is 1.100 g/mL m=nM =(2.70 mol)(36.36g/mol) = 98.4 g % =98.4g x 100 1100g = 8.95% 2.70 mol HCl 1.00 L of solution m=DV =(1.100g/mL)(1000mL) = 1100 g

  15. Titration • Titrations are a chemical procedure involving the addition of a solution of known concentration. The objective is to determine the point in the reaction when the moles of the known solution is equal to the moles of the unknown solution. • The concentration of the unknown solution can be determined by: • Concentrationunknown =Volumeknown x Concentrationknown Volumeunknown

  16. Titration Terminology • Titrant-solution of known concentration. It is added slowly using a burette • Sample-solution of unknown concentration. It is contained in a flask • Primary Standards/Solutions- Solution of know accurate concentrations that are used as titrants.

  17. Titration Terminology • Indicator-A solution that changes color at the equivalence point. • Equivalence Point (Stoichiometric Point)-the amount of titrant required for a complete reaction to occur. (chemically equivalent amounts have reacted). • Endpoint-The point in a titration where a measurable change occurs (indicator change, pH change)

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