Expt 7-Acids, Bases and Salts
-
Upload
twinkledreampoppies -
Category
Documents
-
view
3.355 -
download
1
description
Transcript of Expt 7-Acids, Bases and Salts
![Page 1: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/1.jpg)
Experiment 7: Experiment 7: Acids, Bases Acids, Bases
and Saltsand SaltsGroup # 4 TCD3Group # 4 TCD3
Mateo, Nachura, San DiegoMateo, Nachura, San Diego
![Page 2: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/2.jpg)
Definition of TermsDefinition of Terms• Electrolytes – substances that, when
dissolved in water, results in a solution which conducts electricity
• Nonelectrolytes – substances that, when dissolved in water, gives a solution that does not conduct electricity
![Page 3: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/3.jpg)
Definition of TermsDefinition of Terms• Acids
– Arrhenius: substance that yields H+ when dissolved in water
– Bronsted-Lowry: Proton donor– Lewis: Electron-pair acceptor
![Page 4: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/4.jpg)
Definition of TermsDefinition of Terms• Bases
– Arrhenius: A substance that yields OH- when dissolved in water
– Bronsted-Lowry: Proton acceptor– Lewis: Electron-pair donor
![Page 5: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/5.jpg)
Definition of TermsDefinition of Terms• Salts – An ionic compound made up
of a cation (not H+) and an anion (not OH- or O2-)
![Page 6: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/6.jpg)
Definition of TermsDefinition of Terms• Neutralization reaction – a reaction
between an acid and a base• Titration – The gradual addition of a
solution of accurately known concentration to another solution of unknown concentration until the chemical reaction between the two solutions is complete
![Page 7: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/7.jpg)
ElectrolysisElectrolysis• 5 drops of each was put in a test
tube and tested with indicators – NaOH – NH4Cl– HCl– HC2H3O2
– NaCl– C2H5OH– C2H22O11
![Page 8: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/8.jpg)
Reagents0.1 M
Solutions
Classification (acid, base or neutral)
pH Classification of acid/base (weak or strong)
Conductivity (good,
weak, none)
Classification (strong, weak non-electrolyte)
NaOH Base 14 Strong Good Strong
NH4Cl Acid 3 Strong Good Strong
HCl Acid 1 Strong Good Strong
HC2H3O2 Acid 2 Strong (SHOULD HAVE BEEN WEAK)
Weak Weak
NaCl Neutral 6 Weak Acid (or Neutral) Good Strong
H2O Neutral 7 Neutral None Non-electrolyte
Sucrose Neutral 5 Weak acid (or Neutral) None Non-electrolyte
Ethanol Neutral 6 Weak acid (or Neutral) None Non-electrolyte
HOAc + NaOH
Acid 5 Weak acid (SHOULD HAVE BEEN BASIC)
XXX XXX
HCl + NaOH
Base 13 Strong (SHOULD HAVE BEEN NEUTRAL)
XXX XXX
ResultsResults
![Page 9: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/9.jpg)
ExplanationExplanationBlue litmus paper
Red litmus paper
Congo Red
Phenolphthalein
pH paper
Acid Red Red Blue Colorless
<7
Base Blue Blue Red Pink >7
![Page 10: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/10.jpg)
What happened.What happened.• They were also tested using the
conductivity apparatus
![Page 11: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/11.jpg)
Reagents0.1 M
Solutions
Classification (acid, base or neutral)
pH Classification of acid/base (weak or strong)
Conductivity (good,
weak, none)
Classification (strong, weak non-electrolyte)
NaOH Base 14 Strong Good Strong
NH4Cl Acid 3 Strong Good Strong
HCl Acid 1 Strong Good Strong
HC2H3O2 Acid 2 Strong (SHOULD HAVE BEEN WEAK)
Weak Weak
NaCl Neutral 6 Weak Acid (or Neutral) Good Strong
H2O Neutral 7 Neutral None Non-electrolyte
Sucrose Neutral 5 Weak acid (or Neutral) None Non-electrolyte
Ethanol Neutral 6 Weak acid (or Neutral) None Non-electrolyte
HOAc + NaOH
Acid 5 Weak acid (SHOULD HAVE BEEN BASIC)
XXX XXX
HCl + NaOH
Base 13 Strong (SHOULD HAVE BEEN NEUTRAL)
XXX XXX
ResultsResults
![Page 12: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/12.jpg)
ExplanationExplanation• Electrolytes are substances which
ionize or dissociate in water. The ions are attracted to electrodes in the conductivity apparatus. The movement of ions sets up an electric current and electricity is produced.
![Page 13: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/13.jpg)
ExplanationExplanation• In general:
– acids and bases are electrolytes– strong acids and strong bases: strong
electrolytes– weak acids and weak bases: weak
electrolytes– neutral, ionic substances can also
conduct electricity
![Page 14: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/14.jpg)
Preparation of 1 M NaOHPreparation of 1 M NaOH• Formula
– M = n/L, where M is the molarity of the substance, n is the number of moles, and V is the volume in liters
– g = n x MW (molecular weight)
![Page 15: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/15.jpg)
Preparation of 1 M NaOHPreparation of 1 M NaOH• Calculation
– 1 M NaOH = n / 0.1 L– n = 0.1 mol NaOH– g NaOH = 0.1 mol NaOH x
(40gNaOH/1mol NaOH)– g NaOH = 4 grams
![Page 16: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/16.jpg)
Preparation of 0.1 M NaOHPreparation of 0.1 M NaOH• Formula
– M1V1=M2V2
– M is the molarity of the substance– V is the volume in liters
![Page 17: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/17.jpg)
Preparation of 0.1 M NaOHPreparation of 0.1 M NaOH• Calculation
– M1V1=M2V2
– (0.1M)(100ml) = (1M)(V)– V = 10 ml
![Page 18: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/18.jpg)
Titration of an Acid with a Titration of an Acid with a BaseBase
• Two drops of phenolphthalein was added to the solution of the unknown acid with a volume of 60 ml
• It was carefully titrated with the standardized solution (0.1 M NaOH) until the solution turned a light pink color
![Page 19: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/19.jpg)
Titration of an Acid with a Titration of an Acid with a BaseBase
• This light pink color means that the equivalence point has been reached, meaning the acid has been completely neutralized by the base.
![Page 20: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/20.jpg)
Titration of an Acid with a Titration of an Acid with a BaseBase
Volume of 0.10 M NaOH 11 ml
Volume of unknown acid solution 60 ml
Molarity of unknown acid solution 0.0183 M
Computation:
0.1 M NaOH = (n/.011 L)
n = 1.1 x 10-3 mol
Munknown = (1.1 x 10-3)/(0.060 ml)
M = 0.0183 molar
![Page 21: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/21.jpg)
QuestionsQuestions1. From your results, what
relationship can you draw between the acidity/basicity of a substance and its electrolyte property?
![Page 22: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/22.jpg)
• All acids and bases are electrolytes. The strength of its conductivity is determined by its strength in acidity/basicity. Strong acids and strong bases are strong electrolytes while weak acids and weak bases are weak electrolytes. Not all neutral substances are electrolytes. Neutral, ionic substances are electrolytes and can conduct electricity.
![Page 23: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/23.jpg)
2. Why are electrolytes conductors of electricity?
• Electrolytes are conductors of electricity because they can ionize in water. The ions are attracted to the electrodes, and the movement of the ions sets up an electric current, generating electricity. The electric current set up is equivalent to the flow of electrons along a metal wire.
![Page 24: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/24.jpg)
3. Calculate the pH of the following solutions:
a. 0.001 M HCl[H+] = 0.001 MpH = -log (0.001M)pH = 3
b. 0.005 M NaOH[OH-] = 0.005 MpOH = -log(0.005M)pOH = 2.30pH = 11.70
![Page 25: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/25.jpg)
c. 0.10 M NH4OH solution (Kb = 1.8 x 10-5)
Kb = [NH4+][OH-] = 1.8 x 10-5[NH4OH]Kb = x2 = x2 = 1.8x10-5
0.10-x 0.10x2 = 7.2 x 10-6x = 2.7 x 10-3 MpOH = -log (2.7 x 10-3) = 2.57pH = 14-2.57pH = 11.43
![Page 26: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/26.jpg)
d. 0.02 M HCOOH (Ka = 1.8 x 10-4)
Ka = [COOH-][H+] = 1.8 x 10-4[HCOOH]Ka = x2 = 1.8 x 10-5
0.02-x0 = x2 + (1.8 x 10-5)x – 0.02(1.8 x 10-5)x = -6.09 x 10-4 and/or 5.91 x 10-4x = 5.91 x 10-4 pH = -log(5.91x10-4)pH = 3.23
![Page 27: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/27.jpg)
ConclusionConclusion• Indicators and pH paper are used to
classify acids, bases, and salts.• The conductivity apparatus is used to
classify electrolytes as weak or strong.
![Page 28: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/28.jpg)
• Bases with the highest pHvalues are classified as strong and are good conductors of electricity.
• Acids with the lowest pH values are classified as strong and are good conductors of electricity.
• Weak acids and bases are weak conductors of electricity.
ConclusionConclusion
![Page 29: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/29.jpg)
ConclusionConclusion• Neutral solutions are solutions which
have a pH of 7. Not all neutral solutions can conduct electricity.
![Page 30: Expt 7-Acids, Bases and Salts](https://reader036.fdocuments.net/reader036/viewer/2022062319/553e175f4a795978338b4873/html5/thumbnails/30.jpg)
ConclusionConclusion• By determining the endpoint of an
acid-base titration the concentration of an unknown solution can be known.