chemphys unit 6a: electrolytes

Chemistry & Physics

UNIT 6A: ELECTROLYTES

Chemistry

Periodic table

Chemical reaction

Matter

Atoms

Chemical bonding

Electrolytes

Hydrocarbons

Organic chemistry

PreQuiz (1)

1. Define “ionization”:a) substance conducts electricity; b) substance requires positive/negative charge; c) Net charge of ions is 0

2. Ca2+ is required for

a) enzymes; b) DNA/RNA; c) bones and teeth3. An example of an electrolyte is a(n)

a) acid; b) base; c) salt4. Define “acid”:

a) substance that yields H+ ions in water; b) substance that yields OH- ions in water; c) substance that yields salt in water

5. Weak acidsa) conduct no electricity when ionized in water; b) completely ionize in water; c) partially ionize in water

6. Which of the following compounds is used to treat excess of stomach acida) CaCO3; b) NaCl; c) HCl

7. An example of a base isa) vinegar; b) soda; c) sodium chloride

8. Bases are less dangerous than acids in term of skin contacta) true; b) false; c) who cares

9. The reaction between an acid and base is calleda) equilibrium; b) hydrolysis; c) neutralization

Learning activities (1)

• Electrolytes– Define common terms

• Acids, bases, neutralization– Understand theory of ionization– Identify ions important to human body– Explain properties of acids and bases– Write a neutralization reaction– Discuss the use of acids and bases in body

Electrolytes

DISSOCIATION

IONIZATION

Definitions

• Definition: Ionization– Substance acquires negative/positive charge by gaining/losing electrons

(UNIT 4: Ion formation)– In water: substance breaks up into ions Na+ and Cl-

• Definition: Electrolyte– Substance that undergoes ionization – In water: solution of electrolyte conducts energy– Examples: Salts, acids, bases

Sackheim’s Chemistry: Chapter 11

Salt (NaCl) in water (H2O)

“Ionization of an electrolyte”

Ionization

• Equilibrium– Between ionic compound (NaCl) and free ions (Na+ + Cl-)

• Dissociation– Separation of ions (separation of Na+ and Cl-)


Ionic compound, crystal latticDoes not conduct electricity

Free ions in water solutionDoes conduct electricity

Theory of ionization

• Svante Arrhenius (1887)

Behavior of electrolytes in solution:1. Electrolytes in water: break up into ions

(ionization)2. Ions can have a positive or negative charge3. Negative + positive charges = zero

(molecules are neutral)4. Solutions of electrolytes conduct electricity

(because of ions)5. Nonelectrolytes do not conduct electricity

(because no ions)


Strong vs. Weak electrolytes

• Some electrolytes conduct more electricity than other…?

• Strong electrolytes– Dissociates (breaks up) completely into ions (no equilibrium)

• Weak electrolytes– Disocciates only partially (equilibrium)


Important ions

Ion Symbol Function

Calcium Ca2+ Necessary for clotting blood, digestion, formation of bones and teeth, action of muscle (heart)

Iron Fe2+ Necessary for formation of hemoglobin and cytochromes

Sodium Na+ Extracellular postive ion

Potassium K+ Intracellular positive ion

Chloride Cl- Negative ion

Bicarbonate HCO3- Extracellular negative ion and blood buffer

Iodide I- Present in hormones

Ammonium NH4+ Maintaining acid-base balance

Phosphate PO43- Necessary for formation of bones and teeth

Magnesium Mg2+ Activator for many enzyme systems


Acids and bases

HYDROGEN BONDING

PH VALUE

TITRATION

NEUTRALIZATION

Acids (1)

• Substance that yield hydrogen ions (H+) in water• Common in daily live

– Fruits– Vinegar– Soft drinks– Body

Citric acid

Acetic acid

Phosphoric acid

Hydrochloric acid


Sour taste!

Acids (2)

• Acids donate/yield hydrogen ions (H+) in water

– Strong acids: completely ionized in water

– Weak acids: partially ionized in water

– Diprotic acid: Donate two protons per molecule

hydrogen ion: proton

equilibrium

Monoprotic acids


Antacids

• Stomach secrets acid (digestion of proteins)– Hyperacidity: high HCl concentration– Hypoacidity: low HCl concentration

• Hypoacidity– Dilute HCl to overcome deficiency

• Hyperacidity– Antacids: react with excess stomach acid– TUMS®: CaCO3

acid antacid salt gas water


also used to treat peptic ulcer by decreasing stomach acids

Dangerous

• Strong acids – Aggresive chemicals (corrosive)– Attack clothing

– Damage tissues (skin burn)


Wash with water Treat with NaHCO3

(to neutralize)

Medical use of acids

• Medical importance– Hydrochloric acid (HCl)

• Treat hypoacidity

– Nitric acid (HNO3)• Test presence of albumin (protein) in urine

– Di/tri-chloroacetic acid (C2H2Cl2O2/C HCl O )₂ ₃ ₂• Remove warts

– Hypochlorous acid (HClO)• Disinfect floors and walls hospital

– Boric acid (H3BO3)• Has been used as germicide (to kill microbes)

– Acetylsalicyclic acid (aspirin)• Analgesic (painkiller) and antipyric (against fever)

– Ascorbic acid (vitamin C)• Prevents vitamin C deficiency (scurvy)

Bases (1)

• Substance that yield hydroxide ions (OH-) in water• Common in daily live

– Soap– Houshold ammonia– Baking soda– Bleach

Sodium hydoxide

Sodium bicarbonate

Ammoniumhydroxide

Sodium hypochloride


Bitter taste, slippery feeling

Bases (2)

• Bases yield hydroxide ions (OH-) in water

• More general: bases accept hydrogen ions (H+) in water

yields hydroxide ion

equilibrium

accepts proton

accepts proton

Strong base

Weak base

Dangerous

• Strong bases– Damages tissues (react with proteins/fats)– Serious skin burn

– So: do not wash diapers with strong soap


Wash with water

Medical use of bases

• Medical importance– Sodium hydroxide (NaOH)

• Soap

– Calcium hydroxide (Ca(OH)2)• Overcome excess stomach acidity (antacid)• Antidote to oxalic acid poisening

– Magnesium hydroxide (Mg(OH)2)• Antacid for stomach• Laxative

– Spirits of ammonia (NH4OH and (NH4)2CO3)• Heart and respiratory stimulant


Neutralization reactions

• Acid reacts with base (alkali) to form water and salt:

• Net equation (simplified view):

• Example: “Antacids that neutralize stomach acid”

“NEUTRALIZATION”Acid neutralizes BaseBase neutralizes Acid

Proton (acid)

Hydroxide (alkali)

Water


Acid and base

EXPERIMENT 003Title: Vinegar VulcanoTopic: Acid/base reactions

1. Place a tablespoon of the baking soda into glass

2. Add a few drops of water3. Pour in a dash of the vinegar and

watch the reaction taking place

4. Repeat the experiment, while adding a few drops of soap detergent to the soda/water mixture

What’s happening?

• What is the reason of the foam formation?

– Neutralization reaction: acid + base water + salt (+ gas)– CO2 that is formed creates the foam (as in a glass of coke)– Soap detergent: traps bubbles stable foam

PostQuiz (1)

1. Define “ionization”:a) substance conducts electricity; b) substance requires positive/negative charge; c) Net charge of ions is 0

2. Ca2+ is required for

a) enzymes; b) DNA/RNA; c) bones and teeth3. An example of an electrolyte is a(n)

a) acid; b) base; c) salt4. Define “acid”:

a) substance that yields H+ ions in water; b) substance that yields OH- ions in water; c) substance that yields salt in water

5. Weak acidsa) conduct no electricity when ionized in water; b) completely ionize in water; c) partially ionize in water

6. Which of the following compounds is used to treat excess of stomach acida) CaCO3; b) NaCl; c) HCl

7. An example of a base isa) vinegar; b) soda; c) sodium chloride

8. Bases are less dangerous than acids in term of skin contacta) true; b) false; c) who cares

9. The reaction between an acid and base is calleda) equilibrium; b) oxidation; c) neutralization

The End

chemphys unit 6a: electrolytes

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