Announcements Exam 1 Results: Mean: 71% Range: 39.5%-93.5% Median: 72% Other Bio-LS Class Mean 72% Please read Chapter 4 and complete problems. Please see me for help. There are 3-classes of chemical reactions that occur in aqueous solution. Precipitation Acid-Base Neutralization 1. Precipitation Reaction- an insoluble solid is formed from specific cation-anion combinations. Cations Anions H + ions OH - ions 2. Acid-Base Reaction- a protons donor substance reacts with a hydroxide donor substance forming a salt and water. Insoluble Precipitate Salt and Loss of e - Which is the Gain of e - 3. - Reaction-electron donor substances react with react with substances that accept electrons. Predicted by Solubility Rules Reducing Which is called Oxidizing Learning Check: Does a precipitate form? Write the net M/I and net ionic equation for the reaction of silver nitrate with sodium chromate. Write the net ionic equation for the reaction of silver nitrate with sodium chromate. 1. Write the balanced molecular equation. 2. Write the ionic equation showing the strong electrolytes completely dissociated into cations and anions. 3. Cancel the spectator ions on both sides of the ionic equation to obtain the net ionic equation
Solubility Rules Soluble Ionic Compounds Group IA and NH4 + NO3 - Salts of: C2H3O2 - ClO3 - and ClO4 - Cl -, Br -, I - SO4 Insoluble Ionic Compounds Exceptions Ag +, Pb 2+, Cu +, Hg2 2+ Ca 2+, Sr 2+, Ba 2+ Ag +, Pb 2+ Exceptions Will a precipitate form when Mg(NO3)2 is added to NaOH? A precipitation reaction will occur if can occur. Use the solubility table to judge if it can occur. Salts of: OH - CO3 - PO4 3- S Group IA, Ca 2+, Sr 2+, Ba 2+ Salts of Group IA and NH4 + Salts of Group IA and NH4 + Salts of Group IA, NH4 +, Ba 2+ Ca 2+, Sr 2+ Will a precipitate form when Mg(NO3)2 is added to NaOH? 1. Write a balanced equation 2. Ask whether any combination of ions will be insoluble from a solubity table. If so, the reaction will occur. 3. Write the molecular, ionic and net ionic equations Note ionic species exchanged---called a metathesis reaction Molecular Equation Mg(NO3)2 + 2NaOH ==> Mg(OH)2 + 2NaNO3 Ionic Equation Mg 2+ + 2NO3 + 2Na + + 2OH - ==> Mg Net Ionic Equation Mg 2+ + 2OH - ==> Mg(OH)2 (s) There are 3-classes of chemical reactions that occur in aqueous solution. 1. Precipitation Reaction- an insoluble solid is formed from specific cation-anion combinations. 2. Acid-Base Reaction- a protons donor substance reacts with a hydroxide donor substance forming a salt and water. 3. - Reaction-electron donor substances react with react with substances that accept electrons. Precipitation Acid-Base Neutralization 2. Acid-Base Reactions Cations Anions H + ions OH - ions Insoluble Precipitate Predicted by Salt and Which is the Loss of e - Gain of e - Which is called Solubility Rules Reducing Oxidizing The effects of acid rain on a statue of George Washington taken in 1935 (left) and 2001 (right) marble.
Properties of Acids and Bases Acids: 200 Million Tons H2SO4 Acrid sour taste React with metals giving ion + H 2 gas Changes plant dye litmus from blue to red React with carbonates and bicarbonates to produce CO2 gas Acid Base Bases: 50 Million Tons NaOH Bitter taste Slippery feel Changes plant dye litmus from red to blue React and neutralizes the effects of acids Acids are substances that produce H + when dissolved in water. Acid donates H + HA(g) ==> H + + A - Bases are substances that produce OH - when dissolved in water. MOH(s) ==> OH - + M + Both are strong electrolytes! A - is symbol for halide anion Bases donate OH - M + is symbol for metal cation We must memorize common strong acids and strong bases. All are strong electrolytes that dissociate completely in solution. Strong Acids hydrochloric acid HCl hydrobromic acid HBr hydroiodic acid HI nitric acid HNO 3 sulfuric acid H 2 SO 4 perchloric acid HClO 4 H-X acids Oxide containing acids Strong Bases lithium hydroxide: sodium hydroxide: LiOH NaOH potassium hydroxide: KOH calcium hydroxide Ca(OH) 2 strontium hydroxide Sr(OH) 2 barium hydroxide Ba(OH) 2 Group I and II Hydroxides Anything not strong is weak! Common Weak Acids and Their Anions Acid Anion Anion Name HF F - fluoride ion CH 3 COOH CH 3 COO - acetate ion HCN CN - cyanide ion HNO 2 NO - 2 nitrite ion H 2 CO 3 CO 3 carbonate ion H 2 SO 3 SO 3 sulfite ion H 3 PO 4 PO 4 3- phosphate ion (COOH) 2 (COO) 2 oxalate ion Acids and bases can be classified as strong or weak. We use arrows to symbolize the difference. 100% ionized = strong electrolyte = ==> arrow Strong Acid Strong Base H2SO4(aq) ==> 2H + (aq) + SO4 (aq) KOH(aq) ==> OH - (aq) + K + (aq) <20% ionized = weak electrolyte = <==> arrow Weak Acid Weak Base HNO2(aq) <==> H + (aq) + NO2 - (aq) NH4OH(aq) <==> OH - (aq) + NH4 + (aq)
Determining the Molarity of H + Ions in Aqueous Solutions of Acids Nitric acid is a major chemical in the fertilizer and explosives industries. In aqueous solution, each molecule dissociates and the H becomes a solvated H + ion. What is the molarity of H + (aq) in 1.4M nitric acid? What is the H + molarity of 0.70 M H2SO4? Of H +.466 M H3PO4? Determining the Molarity of H + Ions in Aqueous Solutions of Strong Acids or Bases Nitric acid is a major chemical in the fertilizer and explosives industries. In aqueous solution, each molecule dissociates and the H becomes a solvated H + ion. What is the molarity of H + (aq) in 1.4M nitric acid? One mole of H + (aq) is released per mole of nitric acid (HNO 3 ) HNO 3 (l) H 2 O 1.4M HNO 3 (aq) is 1.4M H + (aq). H + (aq) + NO 3 - (aq) What is the molarity of H + in a 0.70 M H2SO4? Of 2.5 M NaOH? What is the molarity of H + in a 0.466 M H3PO4? Acids and bases react in a must know chemical reaction called a neutralization reaction to form a salt and water. NaOH (aq) + HCl (aq) ==> + Na + + Cl - Chemists use general symbols to represent the neutralization reaction to form a salt and water. NaOH (aq) + HCl (aq) ==> + Na + + Cl - base + acid ==> Water + salt base + acid ==> Water + salt MOH (aq) + HX (aq) ==> + Na + + Cl - A salt is an ionic compound whose cation comes from a parent base and whose anion comes from a parent acid: Alkali Metal Cation Halide Anion Learning check: write the molecular, ionic and net equation for the neutralization between calcium hydroxide and sulfuric acid. 1. The molecular equation shows all reactants and products as undissociated compounds. Learning check: Write molecular, ionic and net equations for the following acid base neutralization reactions. strontium hydroxide(aq) + perchloric acid(aq) Ca(OH)2 (aq) + H2SO4 (aq) ===> 2 + CaSO4 2. The total ionic equation shows all of the soluble ionic substances dissociated into ions. Ca 2+ + 2OH - + 2H + + SO4 ===> 2 + Ca 2+ + SO4 Ca 2+ and SO 4 are spectator ions---they just watch! 3. The net ionic equation eliminate spectator ions and show actual chemical change H + (aq) + OH - (aq) ===> H 2 O(l) barium hydroxide(aq) + sulfuric acid(aq) Nitric acid(aq) + barium hydroxide(aq) Acetic acid(aq) + potassium hydroxide
Writing Ionic Equations for Acid-Base Reactions strontium hydroxide(aq) + perchloric acid(aq) (a) Sr(OH) 2 (aq)+2hclo 4 (aq) (b) Sr 2+ (aq)+2oh - (aq)+ 2H + (aq)+2clo 4 - (aq) (c) 2OH - (aq)+ 2H + (aq) barium hydroxide(aq) + sulfuric acid(aq) (b) Ba(OH) 2 (aq) + H 2 SO 4 (aq) 2H 2 O(l)+Sr(ClO 4 ) 2 (aq) 2H 2 O(l)+Sr 2+ (aq)+2clo 4 - (aq) 2H 2 O(l) 2H 2 O(l) + BaSO 4 (aq) Ba 2+ (aq) + 2OH - (aq)+ 2H + (aq)+ SO 4 (aq) 2H 2 O(l)+Ba 2+ (aq)+so 4 (aq) (c) 2OH - (aq)+ 2H + (aq) 2H 2 O(l) Weak acids dissociate to a very small extent and this fact is reflected in their equations as well using a double-arrow (<==>). Molecular equation NaOH(aq) + CH 3 COOH(aq) Total ionic equation Na + (aq)+ OH - (aq) + CH 3 COOH(aq) Net ionic equation OH - (aq) + CH 3 COOH(aq) CH 3 COONa(aq) + H 2 O Weak acid is not dissociated! CH 3 COO - (aq) + Na + (aq) + H 2 O(l) CH 3 COO - (aq) + H 2 O(l) Learning Check: Acids and Bases 1. Name and characterize each as a base, acid or salt? Chemists symbolize the reactions of acids with water two equivalent ways. Don t let it bug you. HF(g), HI(aq), LiOH(aq), Mg(OH)2, Na2SO4 CH3COONH4 2. Name and classify the following as strong, weak acid or base? HClO4, Sr(OH)2, HClO2, NH3(g), H3PO4(aq), H2SO4(aq), HNO3 (aq) 3. Write the M/I/NI equation for the reactions of a) hydrochloric acid with calcium hydroxide and b) phosphoric acid with sodium hydroxide 4. What acids and bases were reacted to form the following salts? Show using balanced equations. 1) NaNO2 2) CaSO4 3) Mg(PO4)2 H + representation HCl(g) ===> H + + Cl - HNO3(l) ===> H + + NO3 - HA(g) ===> H + + A - Generalized Acid HA H 3O + Representation HCl(g) + => H3O + + Cl - HNO3(g) + => H3O + + NO3 - HA(g) + => H3O + + A - Generalized Acid HA Quiz 3 Please put your books away! Full-sheet of paper with name on top! Time is 10 minutes Given the following reaction: N2(g) + H2(g) ==> NH3(g) Mol Mass (g/mol): N2 = 28.01; H2 = 2.016; NH3 = 17.03 (1) Balance the equation: N2(g) + H2(g) => NH3(g) (1.5 pts). (2) If 1.0 g of N2 is reacted with excess H2, how many moles of NH3 can be produced? (2 pts) (3) If 1.0 g of H2 is reacted with excess N2, how many moles of NH3 can be produced? (1.5pts) (4) Suppose reacting 2.0 g of N2 with excess H2 produces 2.4 g of NH3, while reacting 2.0 g of H2 with excess N2 produces 11 g of NH3. If 2.0 g of N2 is reacted with 2.0 g of H2, is N2 or H2 the limiting reagent? (1 pt) (5) How many H atoms are in 1.0 g of NH3? (4 pts)