Unit 7

Niamat UllahPost Rn BScN

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ACID BASE CONCEPT TYPES OF SALT BUFFER AND ITS TYPES RELATION WITH

RESPIRATORY AND RENAL SYSTEM

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Acid: a substance that produces H+ when dissolved in water (e.g., HCl, H2SO4)

Base: a substance that produces OH- when dissolved in water (NaOH, KOH)

What about water?

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Acids – produce H+

Bases - produce OH-

Acids – donate H+

Bases – accept H+

Acids – accept e- pair Bases – donate e- pair

Arrehenius

Bronsted-Lowry

Lewis

only in water

any solvent

used in organic chemistry,wider range of substances

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The Swedish chemist Svante Arrhenius proposed the first definition of acids and bases.(Substances A and B becameknown as acids and bases)According to the Arrhenius model:

“acids are substances that dissociate in water to produce H+ ions and bases are substances that dissociate in water to produce OH- ions”

NaOH (aq) Na+ (aq) + OH- (aq) Base

HCl (aq) H+ (aq) + Cl- (aq) Acid5LIFE SAVING SON

+e-

+

Hydrogen (H) Proton (H+)

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Unknown to Arrhenius free H+ ions do not exist in water. They covalently react with water to produce hydronium ions, H3O+.

or:H+ (aq) + H2O (l) H3O+ (aq)

This new bond is called a coordinate covalent bond since both new bonding electrons come from the same atom

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Memorized Strong Acids1. HClO4

2. H2SO4

3. HI

4. HBr

5. HCl

6. HNO3

Memorized Strong BasesHydroxides of group 1 and 2metals, excluding Be and Mg

Strong Acids and Bases

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Johannes Brønsted and Thomas Lowry revised Arrhenius’s acid-base theory to include this behavior. They defined acids and bases as follows:

“An acid is a hydrogen containing species that donates a proton. A base is any substance that accepts a proton”

HCl (aq) + H2O (l) Cl- (aq) + H3O+ (aq)

In the above example what is the Brønsted acid? What is the Brønsted base?

Bronsted Lowry

Bronsted Lowry Theory

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The Brønsted-Lowry acid: any substance able to give a hydrogen ion (H+-a proton) to another molecule◦ Monoprotic acid: HCl, HNO3, CH3COOH

◦ Diprotic acid: H2SO4

◦ Triprotic acid: H3PO3

Brønsted-Lowry base: any substance that accepts a proton (H+) from an acid◦ NaOH, NH3, KOH

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A proton is transferred from one substance (acid) to another molecule

Ammonia (NH3) + acid (HA) → ammonium ion (NH4+) + A-

◦ Ammonia is base◦ HA is acid

◦ Ammonium ion (NH4+) is conjuagte acid

◦ A- is conjugate base

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In the early days of chemistry chemists were organizing physical and chemical properties of substances. They discovered that many substances could be placed in two different property categories:

Substance A

1. Sour taste

2. Reacts with carbonates to make CO2

3. Reacts with metals to produce H2

4. Turns blue litmus pink

5. Reacts with B substances to make salt water

Substance B

1. Bitter taste

2. Reacts with fats to make soaps

3. Do not react with metals

4. Turns red litmus blue

5. Reacts with A substances make salt and water

Arrhenius was the first person to suggest a reason why substances are in A or B due to their ionization in water.

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Electrolytes◦ Cations: sodium, potassium, hydrogen, magnesium,

and calcium◦ Anions: chloride, bicarbonate, phosphate, and sulfate

Non-electrolytes◦ Glucose◦ Urea◦ Protein◦ Lipids◦ Creatinine

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Major electrolytes

1 Eq mEq/L Physiological gram

Na+ = 23.1 g 136-145 ?

Cl- - 35.5 g 98-106 ?

Mg+2 (24.3)/2 = 12.15 g 3 ?

Ca2+ (40.1/2) = ~20.05 g

4.5-6.0 ?

K+ 39.1 g 3.4-5.0 ?

HCO3- 61 g 25-29 ?

SO3-2 and HPO43- 2 ?

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pH

2 3 4 5 6 7 8 9 10 11 12

neutral @ 25oC(H+) = (OH-)

distilled water

acidic(H+) > (OH-)

basic or alkaline(H+) < (OH-)

natural waters pH = 6.5 - 8.5

normal rain (CO2)pH = 5.3 – 5.7

acid rain (NOx, SOx)pH of 4.2 - 4.4 in Washington DC area

0-14 scale for the chemists

fish populationsdrop off pH < 6 and to zero pH < 5

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Salts are the ionic product of an acid base neutralization reaction.

Acidic Salts are formed from a strong acid and a weak base.

Neutral salts are formed from a strong acid and strong base.

Basic salts are formed from a strong base and a weak acid.

Give the acid and base the following salts were formed from and label the salts as acidic, basic, or neutral.

1. NaCl

2. NaC2H3O2

3. NH4Cl

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1. NaCl

1. NaC2H3O2

1. NH4Cl

NaCl + HOHReactants are?

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1. NaCl

2. NaC2H3O2

3. NH4Cl

NaCl + HOHHCl + NaOH

NaC2H3O2 + HOH

S.A. s.b.

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1. NaCl

2. NaC2H3O2

3. NH4Cl


NaC2H3O2 + HOH

S.A. s.b.Neutral salt

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1. NaCl

2. NaC2H3O2

3. NH4Cl


NaC2H3O2 + HOHHC2H3O2 + NaOH

Neutral salt s.a. s.b.

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1. NaCl

2. NaC2H3O2

3. NH4Cl


NaC2H3O2 + HOHHC2H3O2 + NaOHw.a. s.b.


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1. NaCl

2. NaC2H3O2

3. NH4Cl


NaC2H3O2 + HOHHC2H3O2 + NaOHw.a. s.b.basic salt


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1. NaCl

2. NaC2H3O2

3. NH4Cl




NH4Cl + HOH25LIFE SAVING SON






1. NaCl

2. NaC2H3O2

3. NH4Cl




NH4Cl + HOHNH4OHHCl +26LIFE SAVING SON






1. NaCl

2. NaC2H3O2

3. NH4Cl




NH4Cl + HOHNH4OHHCl +s.a. w.b.

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1. NaCl

2. NaC2H3O2

3. NH4Cl



neutral salt s.a. s.b.

NH4Cl + HOHNH4OHHCl +s.a. w.b.acidic salt

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Three Types:Bicarbonate Buffers

Phosphate BuffersProtein Buffers

WHAT IS BUFFER?

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Buffer solution is typically made by mixing a weak acid and one of its salts OR mixing a weak base with one of its salts. Another way of saying this is that a buffer solution consists of a mixture of a weak acid and its conjugate base OR a weak base and its conjugate acid.

Example: Consider a solution containing both acetic acid, CH3COOH, and acetate ions, CH3COO-. (Alternatively, these could be called ethanoic acid and ethanoate ions.) This solution could be made by dissolving sodium acetate (sodium ethanoate) in acetic acid (ethanoic acid).Any strong base that is added to the solution is neutralized by the acetic acid:

CH3COOH (aq) + OH-(aq) CH3COO-

(aq) + H2O (aq31LIFE SAVING SON

Any strong acid that is added to the solution is neutralized by the acetate:

CH3COO-(aq) + H+

(aq) CH3COOH (aq)

The amount of strong acid or base that a buffer can neutralize is called the buffer capacity.

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Major extracellular buffering system

HCO3- functions as a weak base while H2CO3

functions as a weak acid.

Example:HCl + NaHCO3- H2CO3 + NaCl

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Important in urine and intracellular buffering systems

However NaH2PO4 acts as the weak acid and Na2HPO4 serves as the weak base.

Example:HCl + Na2HPO4 NaH2PO4 + NaCl

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Most abundant buffering system in the body including intracellular and extracellular compartments.

Carboxyl groups (COOH) and amine groups (NH3) act as either an acid or a base respectively.

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Two Types:Respiratory Buffering System

Renal Buffering System

Rising plasma H+ causes deeper, rapid breathing which decreases CO2 blood thereby decreasing H+ ions.

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Reabsorption of HCO3- is coupled to H+ secretion

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Respiratory acidosis Increased CO2=increased H+=decreased pH Cause: Hypoventilation To compensate: Kidney function=increase excretion of H+ or

by increased reabsorption of HCO3-

Respiratory alkalosis Decreased CO2=decreased H+=increased pH Cause: Hyperventilation To compensate: Kidney function=decreased H+ excretion or

by decreased reabsorption of HCO3-

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Metabolic acidosis Decreased HCO3

-=increased H+=decreased pH

Cause: Diarrhea, ketosis, renal dysfunction To compensate: Hyperventilation and kidney function

Metabolic alkalosis Increased HCO3

-=decreased H+=increased pH

Cause: Vomiting, diuretics, alkaline drug use To compensate: Hypoventilation and kidney function

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Unit 7

Healthcare

life saving sonlife

h acids

h bases

substance acid

h aq h2o

brnsted acid

hydrogen ion h

b substances