ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very...

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ABC’s of pH Acids and Bases Revised 10-03-2006

Transcript of ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very...

Page 1: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

ABC’s of pH

Acids and Bases

Revised 10-03-2006

Page 2: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Homeostasis

• Chemical reaction in the body are very sensitive to changes in pH.

Page 3: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

pH values in Body

• Gastric Juices 1.2 - 3.0• Urine 4.6 – 8.0• Saliva 6.35 - 6.85• Blood 7.35 – 7.45• Spinal Fluid 7.4• Pancreatic Juice 7.1 – 8.2• Bile 7.6 – 8.6

Page 4: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

pH

• pH is based on the relative concentration of hydrogen ions (H+ or H3O+) in a solution.

Water ionizes into H+ and OH-

H2O H3O+ + OH-

Page 5: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Scientists measure the pH of solutions using a pH meter

The meter reads the H+ ion concentration in solution indicating the pH of the solution.

Page 6: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Mathematically it is

• pH is based on the relative concentration of hydrogen ions in a solution.

pH = -log [H+]• Water at 25oC contains 1/10,000,000 mole of H+ ions = 10 -7 moles/liter

pH = -log [10-7]pH = 7

Page 7: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

pH

Page 8: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

logarithmic• a pH of 6 is ten times more acidic than

distilled water.

• Also, a solution that has a pH of 8 is ten times more basic (alkaline) than distilled water.

• Likewise, a solution that has a pH of 4 is 100 times more acidic than one which has a pH of 6.

Page 9: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• The pH scale is logarithmic (that's what the "p" stands for; the "H" is short for hydrogen);

• therefore, a solution that has a pH of 6 is ten times more acidic than distilled water.

• Also, a solution that has a pH of 8 is ten times more basic (alkaline) than distilled water.

• Likewise, a solution that has a pH of 4 is 100 times more acidic than one which has a pH of 6.

Page 10: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Properties of Acids

• Substances with a pH below 7 are acids. • An acid is any substance that ionizes (release charged

particles when dissolved) in water to produce H+ hydrogen ions or free protons in water.

• Acids tend to taste sour. • Change blue litmus paper to red.• React with metals to release hydrogen gas.• Neutralize bases, forming water and salts

• Acidic solutions have concentrations of H3O+ above 1 X 10-7

Page 11: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Acid Examples

stomach juices hydrochloric acidHCl H+ + Cl-

battery acid sulfuric acidH2SO4 2H+ + SO4

2-

vinegar acetic acidCH3COOH H+ + CH3COO-

Page 12: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Measuring Acidity

• Added acids increase [H3O+]

• In acid solutions [H3O+] > 1 x 10-7 M

• pH scale measures acidity without using exponential numbers.

Page 13: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Acid pH Calculations

• [H3O+]=1 x 10-5 M, pH = ?

• 5 (acidic)

• [H3O+]=2.6 x 10-5 M, pH = ?

• 4.59 (acidic)

• [H3O+]=7.8 x 10-3 M, pH = ?

• 2.11 (acidic)

Page 14: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Properties of Bases

• have a pH greater than 7. • A base is a substance that ionizes in water solution to

produce OH- hydroxide ions. • Bases tend to feel slippery to the skin.• Bases accept protons• Bitter taste• Bases turn red litmus paper blue.• Neutralize acids, forming water and salts.

• Basic solutions have H3O+ concentrations less than 1 X 10-7

Page 15: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Base ExamplesMilk of Magnesia

Mg (OH)2 2OH- + Mg2+

Mylanta

Mg (OH)2 + Al(OH)3 5OH- + Mg2+ + Al3+

Maalox

Mg (OH)2 + Al(OH)3 5OH- + Mg2+ + Al3+

Page 16: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Measuring Acidity

• Added bases increase [OH-].

• In basic solutions [OH-] > 1 x 10-7 M

[H3O+] < 1 x 10-7 M

• pH scale measures acidity without using exponential numbers.

Page 17: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Base pH Calculation [H3O+] to ph

• [H3O+]=1 x 10-10 M, pH = ?

• 10 (basic)

• [H3O+]=6.3 x 10-9 M, pH = ?

• 8.20 (basic)

• What if the number is not 1?

Page 18: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

pH Calculations

• pH to [H3O+]?

– inverse log of negative pH– orange juice, pH 3.5 [H3O+]=?

• [H3O+] = 10-3.5 = 3.2 x 10-4 M

– saliva, pH 6.2 [H3O+]=?

• [H3O+] = 10-6.2 = 6.3 x 10-7 M

Page 19: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• Strong acids ionize completely in water

• Weak acids ionize only partially in water

• Strong bases ionize completely in water.

• Weak bases ionize only partially in water.

Strong and Weak Acids and Bases

Page 20: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Neutralization

• Acids and bases can neutralize each other by forming water and salt.

• Salt - a crystalline compound composed of the negative ion of an acid and the positive ion of a base.

H+A- + B+OH- H20 + A-B+ (salt)

Page 21: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Examples

Stomach acid + Milk of Magnesia H20 + salt

Hydrochloric Acid + Magnesium Hydroxide H20 + salt

2HCl + Mg(OH)2 2H20 + MgCl2

Stomach acid + Mylanta H20 + saltHydrochloric Acid + Magnesium Hydroxide and Aluminum Hydroxide H20 + salt

5HCl + Mg(OH)2 and Al(OH)3 5H20 + MgCl2 + AlCl3

Page 22: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Buffer

• Buffers act as a reservoir for hydrogen ions, donating or removing them from solution as necessary.

• a solution that can receive moderate amounts of either acid or base without the significant change in its pH.

Page 23: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Buffer

• A buffer is a mixture of a weak acid with the salt of the acid.

• If small amounts of acid is added, hydronium ions are neutralized by reacting with the salt in solution

• If small amounts of base is added, hydroxide ions are neutralized by reacting with the acid.

Page 24: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Protein Buffer System

• Intracellular Fluid

• Blood Plasma

• Red Blood Cells– Hemoglobin

• Blood Plasma– Albumin

Page 25: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Protein Buffer Systems

• carboxyl group (—COOH)

• amino group (—NH2);

Page 26: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Protein Buffer Systems

• carboxyl group (—COOH)

–Releases H+ ↑pH

Page 27: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Protein Buffer Systems

• amino group (—NH2);

–Forms NH3+ ↓pH

Page 28: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

20 Amino Acids

Page 29: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Hemoglobin

Page 30: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• The protein hemoglobin is an important buffer of H+ in red blood cells. As blood flows through the systemic capillaries, carbon dioxide (CO2) passes from tissue cells into red blood cells, where it combines with water (H2O) to form carbonic acid (H2CO3). Once formed, H2CO3 dissociates into H+ and HCO3-.

Page 31: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• At the same time that CO2 is entering red blood cells, oxyhemoglobin (Hb-O2) is giv ing up its oxygen to tissue cells. Reduced hemoglobin (deoxyhe-moglobin) is an excellent buffer of H+, so it picks up most of the H+. For this reason, reduced hemoglobin usually is written as Hb-H. The following reactions summarize these relations

Page 32: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Hemoglobin• Brown

• 65,000 Daltons

• 4 sub units

Page 33: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Hemoglobin

Page 34: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Carbonic Acid- Bicarbonate

• Carbonic acid – H2CO3

– weak acid

• Bicarbonate ion – HCO3

-

– weak base

Page 35: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Carbonic acid-bicarbonate buffer system

Page 36: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

carbonic acid-bicarbonate buffer system

Page 37: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Carbonic Acid- Bicarbonate

Page 38: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Carbonic Acid- Bicarbonate

Page 39: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

carbonic acid-bicarbonate buffer system

Page 40: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Phosphate Buffering System

Page 41: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Phosphate Buffering System

Page 42: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.
Page 43: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.
Page 44: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Phosphate Buffering System

• Intracellular Fluid

• Cytosol

• Kidneys

Page 45: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Exhalation of CO2

Page 46: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Breathing and pH levels

Page 47: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Negative Feedback Loop

Page 48: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Kidney Excretion of H+

Page 49: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.
Page 50: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.
Page 51: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Summary of Mechanisms that Maintain pH of Body FluidsMechanism Comments

Buffer Systems Most consist of a weak acid and the salt of that acid, which functions as a weak base. They prevent drastic changes in body fluid pH.

Proteins The most abundant buffers in body cells and blood. Histidine and cysteine are the two amino acids that contribute most of the buffering capacity of proteins. Hemoglobin inside red blood cells is a good buffer.

Page 52: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Summary of Mechanisms that Maintain pH of Body Fluids

Mechanism Comments

Carbonic acid-bicarbonate

Important regulator of blood pH. The most abundant buffers in extracellular fluid (ECF).

Phosphates Important buffers in intracellular fluid and in urine.

Page 53: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Summary of Mechanisms that Maintain pH of Body Fluids

Mechanism Comments

Exhalation of CO2

With increased exhalation of C02, pH rises (fewer H+).

With decreased exhalation of CO2, pH falls (more H+).

Kidneys Renal tubules secrete H+ into the urine and reabsorb HCO3

-

so it is not lost in the urine.

Page 54: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

pH Summary

• Acids dissociate in water to increase the concentration of H+.– pH values lower than 7

• Bases combine with H+ ions when dissolved in water, thus decreasing H+ concentration.– pH values above 7

• Buffers act as a reservoir for hydrogen ions, donating or removing them from solution as necessary.

Page 55: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Calibration of pH Meter

• Use pH standards

–pH 7

–pH 10

Page 56: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Calibrate pH Meter

Page 57: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• Steps:• Turn the pH meter on by pressing the

“on/off” button.• Remove the pH electrode from the green

pH 7 solution and rinse the electrode well with distilled water into the “waste” 600ml beaker.

• .

Page 58: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

• Place the electrode into the orange pH 4 solution, and press “cal”. Observe the digital numbers in the readout window, when the numbers stop changing press the “read” button. The display should now read 4.00

Page 59: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Rinse Electrode each time

Page 60: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Calibrate pH Meter

Page 61: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.
Page 62: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

24 well container

Page 63: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Read pH of Solutions

Page 64: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Ammonia

• Predict pH

Page 65: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Apple Juice

• Predict pH

Page 66: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Baking Soda

• Predict pH

Page 67: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Berry Juice

• Predict pH

Page 68: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Bleach

• Predict pH

Page 69: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Grapefruit Juice

• Predict pH

Page 70: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Mylanta

• Predict pH

Page 71: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Phillips’ Milk of Magnesia

• Predict pH

Page 72: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Tomato Juice

• Predict pH

Page 73: ABC’s of pH Acids and Bases Revised 10-03-2006. Homeostasis Chemical reaction in the body are very sensitive to changes in pH.

Vinegar

• Predict pH