美国高中化学酸碱反应 Acid-Base Reactions

NaOH + HC2H3O2H2O + NaC2H3O2
Buffers in the Blood
• Blood must keep a pH of 7.4 to allow the best exchange of CO2 and O2 • Blood buffer is HCO3-/H2CO3 • Add Base: H2CO3+OH-HCO3-+H2O • Add Acid: HCO3-+H+H2CO3 • What happens when you take in too much CO2?
• HCl(aq) + Al(OH)3(s) • Weak bases wont completely dissociate
Strong Acid + Weak Base
– Cannot write them as ions on reaction side of net ionic equation
• How do we know the Standard solution is neutral? • pH Indicators酸碱指示剂
• End point • Equivalence point • Neutral po来自百度文库nt
– Volume of acid/base used gives us molarity – MAVA = MBVB
Titrations practice
• If 15.0 mL of 0.50 M NaOH is used to neutralize 25.0 mL of HC2H3O2, what is the molarity of the acid solution? NaOH + HC2H3O2 H2O + NaC2H3O2; 1:1 ratio • MAVA = MBVB • MA= MBVB/VA = (0.50 M)(15.0 ml)/25.0 ml = 0.30 M • If 25.0 mL of a standard 0.05 M HCl solution is required to neutralize 20.0 mL of a solution of Sr(OH)2, what is the concentration of the base? 2 HCl + Sr(OH)2 SrCl2 + 2H2O; 2:1 ratio • MAVA = 2 MBVB • MB = MAVA/2VB = (0.05 M)(25.0 ml)/(2)(20.0 ml) = 0.03 M
H2O
• Test to determine the molarity of an acid or a base • Process:
Titrations滴定
– Find the Standard Solution标准溶液 – Standard solution of an acid/base is slowly added to an acid/base of unknown molarity – When the unknown acid/base is neutral, the [H+]=[OH-]
Weak Acid + Strong Base
• HC2H3O2(aq) + NaOH(aq) • Weak acid wont completely dissociate
– Wont breakdown into ions on reaction side HC2H3O2(aq) + Na+(aq)+OH-(aq)Na+(aq)+C2H3O2-(aq)+ H2O(l)
HC2H3O2(aq) +OH-(aq)C2H3O2-(aq)+ H2O(l) • End solution is slightly basic Weak Acid + Weak Base ???Not clear??? • Both the acid and base are so unreactive there is little change • Not common reaction type in nature
• Acids produce H+ ions when added to water • Bases produce OH- ions when added to water HCl(aq)+H2O(l)H3O+(aq)+Cl-(aq)
ACID BASE Conjugate acid Conjugate base
Acid-Base Reactions Ch. 15
• Neutralization reactions中和反应
– pH is changed
Acid-Base Reactions
• Produce a salt and H2O
• 2 types of Acids
– Strong and Weak
H+(aq)+Cl-(aq)+Al(OH)3(s)Al+3(aq)+Cl-(aq)+H2O(l) H+(aq)+Al(OH)3(s)Al+3(aq)+H2O(l) • End solution is slightly acidic • What about NH3?
– Considered a weak base but has no OH– Does not produce water H+(aq)+Cl-(aq)+NH3(aq)NH4++Cl-(aq) H+(aq))+NH3(aq)NH4+ – HCl(aq)+NH3(aq)NH4Cl(aq)
– Weak acid or base produced from an acid-base reaction
Regulating pH
• Living things interact with acids and bases all the time; their pH must be regulated • Buffer
– Salts are ionic compounds
• 2 types of Bases
– Strong and Weak
• 4 possible combinations of Acids and Bases
– – – – Strong A + Strong B Strong A + Weak B Weak B + Strong B Weak B + Weak A
Bronsted-Lowery Acids and Bases
H2O(l)+NH3(aq)NH4+(aq)+OH-(aq)
ACID BASE Conjugate acid Conjugate base
• • • •
Acid= Any compound that releases H+ Base= Any compound that takes H+ Water can act as an acid or a base Conjugate Acid/Base
– H2CO3 increases making blood more acidic
• What kind of blood pH results in yawning?
– Acidic blood; body needs to release large amount of CO2 by taking in large amount of O2
Antacids抗酸剂
• Compound controls acidic pH levels by adding base • 2 types: – Hydroxide Antacids • Low solubility in water • Release OH- to neutralize H+ • Milk of Magnesia (Mn(OH)2) – Carbonate Antacids • XCO3 or XHCO3; react with HCl Breaks down to CO2 and • CaCO3 + 2HClCaCl2 + H2CO3
Strong Acid + Strong Base
• HCl + NaOH NaCl + HOH • Double replacement reaction • Both compounds completely dissociate
HCl Cl- + H+ NaOH Na+ + OH-
• Complete equation (aq) can be written: H++Cl-+Na++OH-Cl-+Na++H2O • Spectator Ions
Add a strong base: HC2H3O2(aq)+NaOH(aq) C2H3O2-(aq)+H2O(l) HC2H3O2(aq)+OH-(aq) C2H3O2-(aq)+H2O(l)
• Weak acid/base + salt of that acid/base NaC2H3O2 and HC2H3O2
– Solution that adjusts to the addition of acids and bases to slowly change the pH Add a strong acid: - and H+ ions – Free OH NaC2H3O2(aq)+HCl(aq)
HC2H3O2(aq)+NaCl(l) C2H3O2-(aq)+H+(aq)HC2H3O2(aq)
HBr: NaOH + HBr NaBr + H2O; strong
b) what is the concentration of the acid used?
MA= MBVB/VA = (0.5M)(35ml)/50ml = 0.35 M
– Ions that do not take part in the reaction
Net Ionic Equations净离子方程式
1) Write Complete Ionic Equation
All soluble compounds are shown as free ions
2) Remove Spectator Ions Ions not directly evolved in the rxn. 3) Balance the remaining rxn.
• What types of acid-base reactions do these titration graphs show?
Titrations practice
Titrations practice
• Graphs shows titration of 0.5 M NaOH with 50ml of an unknown acid. After titration NaBr salt crystals were isolated from the solution. a) What is the acid used? Is it strong or weak?
Strong Acid + Strong Base
• What is the net ionic equation: HCl(aq) + NaOH(aq) 1) H+(aq) +Cl-(aq) +Na+(aq) +OH-(aq) Cl-(aq) +Na+(aq) +H2O(aq) 2) H+(aq) +OH-(aq) H2O(l) • All strong acid and strong base reactions have this as a base net ionic equation KOH(aq)+HNO3(aq)KNO3(aq)+H2O(l) K++OH-+H++NO3- K++NO3-+H2O(l) OH-+H++ H2O(l)