Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Electrochemistry wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
Stability constants of complexes wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Sulfuric acid wikipedia , lookup
Acid-Base Reactions - Definitions Assume the acids and bases are in water. acid Arrhenius: donates H+ base donates OH– Bronsted-Lowry donates H+ accepts H+ Lewis: electron pair acceptor electron pair donor (classic: NH3) Acid Dissociation + H 1- HCl Cl Acid Conjugate base Conjugate pair Kelter, Carr, Scott, Chemistry A World of Choices 1999, page 280 Conjugate Acid-Base Pairs Use Brønsted–Lowry Definitions of Acid & Base conjugates base HCl + H2O conj. acid H3O+ + acid Clconj. base conjugates HCl acid + H2O H3O+ base CA + ClCB Conjugate Acid-Base Pairs conjugates acid NH3 + H2O base base NH41+ + OH- acid conjugates NH3 base + H2O acid NH41+ CA + OHCB Conjugate Acid-Base Pairs: Direction of Reaction The reaction proceeds in the direction such that the stronger acid donates its proton to the stronger base. HCl + H2O acid base H3O1+ CA + ClCB Amphoteric: A substance that can act as either an acid or a base. 1. Water can act as an acid: H+ 2. Water can act as a base: + H S Water is amphoteric. Zwitterion: A neutral molecule with both positive and negative electrical charges. acid conj. acid example: amino acid (glycine) base cong. base Strong Acids & Bases Strong Acids HCl HBr HI HNO3 HClO3 H2SO4 Strong Bases Group 1 LiOH NaOH KOH (Rb & Cs) Heavy Group 2 Ca(OH)2 Sr(OH)2 Ba(OH)2 Strong acids & bases completely dissociate (e.g., HCl -> H+ + Cl–) Weak acids & bases don’t “ “ (e.g., HF H+ + F – ) Types of Acid-Base Reactions Types: (1) strong acid + strong base (2) weak acid + strong base (3) strong acid + weak base [(4) weak acid + weak base] {treated separately with titration} (N.B., general formulas for acid = HB dissociates into H+ and B–) Strong Acid + Strong Base 1. strong acid + strong base (using HCl and NaOH as examples) Both completely dissociate in water before the reaction occurs. HCl + NaOH H+(aq) + Cl–(aq) + Na+(aq) + OH–(aq) 2. net ionic equation: H+(aq) + OH–(aq) H2O(l) (Na+ and Cl– are spectator ions) (neutralization reaction) Weak Acid + Strong Base acetic acid, HC2H3O2, and NaOH as an example. HC2H3O2 + NaOH (A) Two reactions occur: (1) weak acid: (2) strong base: ? HC2H3O2 H+ + C2H3O2– (reversible reaction) (NaOH is completely dissociated so it is Na+ + OH–) NaOH Na+ + OH– (S) overall reaction: Na+ + OH– + H+ + C2H3O2– Na+ + H2O + C2H3O2– (B) net ionic equation: HC2H3O2 + OH– C2H3O2– + H2O(l) (Na+ is a spectator ion.) Practice Write the net ionic equation for sulfuric acid and barium hydroxide: H2SO4 + Ba(OH)2 strong acid strong base 2H+ + 2OH– -> 2H2O Practice Ex. 4.3: Write the net ionic equation for the following reaction: a) Hypochlorous acid + barium hydroxide weak acid strong base HClO2 + OH– -> ClO2– + H2O Strong Acid + Weak Base (2)HCl and NH4 as examples HCl + NH3 Two reactions occur: (1) weak base: (2) strong acid: Overall Reaction: net ionic equation: NH3 + H2O NH4+ + OH– (reversible reaction) HCl H+ + Cl– NH3 + H2O + H+ + Cl– NH4+ + H2O + Cl– H+ + NH3 NH4+ (H2O from H+ + OH–) (Cl– is a spectator ion) Practice Ex. 4.3: Write the net ionic equation for each of the following: a) Hypochlorous acid + barium hydroxide weak acid strong base 2H+ + 2OH– -> 2H2O H+ + OH– -> H2O Acid-Base Titration Commonly used to determine the concentration of a solution. https://youtu.be/wQ98RfLJ5Uk?list=PLnEQfEiSza7A2yiSG8sun5YGxJ1sg0Rwe Acid-Base Titration Titration: Measuring the concentration of an unknown using the volume and concentration of a standard solution of known concentration. Objective: To determine the point at which the reaction is complete. Equivalence point. Acid-Base Titration What is the molar mass of H2X of 29.45 mL of 0.187 M NaOH are required to neutralize a solution prepared by adding 0.242 g of H2X to enough water to make 25.00 mL of solution? Plan: Determine number of moles of H2X Then you can calculate the mass, molar mass, and even volume or molarity. number of moles NaOH moles OH– (Then 25.00 mL volume is irrelevant.) mole H2X MM mole H2X Acid-Base Titration What is the molar mass of H2X of 29.45 mL of 0.187 M NaOH are required to neutralize a solution prepared by adding 0.242 g of H2X to enough water to make 25.00 mL of solution? mol H2X: MM H2X: