Acids, Bases and pH scale

Main Idea: Life is dependent on the proper pH

ACIDS Compounds that release Hydrogen ions (H+)

Examples of Common Acids Hydrochloric acid – HCl Hydrosulfuric acid – H 2 SO 4 Nitric acid – H 2 NO 3 What do these formulas have in common? Usually begin with an “H”

Acetic Acid - Vinegar HC 2 H 3 O 2

Salicylic Acid Natural Source – Willow bark Used in aspirin and blemish cremes

Lactic Acid Found in yogurt, cottage cheese and sourdough bread Causes muscle “burn” when it builds up inside cells

Citric Acid Found in citrus fruits (lemons, oranges, grapefruit) Flavoring in soft drinks

Formic Acid Produces the burning sensation in the venom of ants and bees HCO 2 H

Amino Acids “Building blocks” of protein molecules

Nucleic Acids Deoxyribonucleic Acid DNA Ribonucleic Acid RNA

Bases Bases are compounds that release Hydroxide ions (OH -). Also called alkalines.

Examples of Common Bases Sodium hydroxide – NaOH Calcium hydroxide – CaOH Magnesium hydroxide – Mg(OH) 2 Most soaps and detergents are basic

All compounds are either Acids, Bases, or Neither HF H 2 SO 4 CaOH Mg(OH) 2 C 6 H 12 O 6 HCl NaCl Al(OH) 2 Chemical Formula Acid Base Neither

All compounds are either Acids, Bases, or Neither HF XX H 2 SO 4 XX CaOH XX Mg(OH) 2 XX C 6 H 12 O 6 XX HCl X NaCl XX Al(OH) 2 XX Chemical Formula Acid Base Neither

pH A measurement of the amount of H+ (hydrogen ions) in a given solution

pH Scale - Range is __

pH Acid Base Neutral Determining a compound ’s identity from its pH value

1.3 XX XX XX 0.1 XX XX 3.89 XX 13.0 XX 0.0 XX 7.0 XX pH Acid Base Neutral Determining a compound ’s identity from its pH value

Most living things must live in an environment of pH 6.5 – 7.5

Blood pH and Buffers Normal pH of blood between Less than 6.8 or greater than 7.8 is deadly Natural Buffers in your body help prevent any large change in blood pH

Buffers Chemicals that prevent any large changes in pH – help to maintain homeostasis They bind to an H+ ion when the H+ concentration increases - “locks” it up so the solution doesn’t get more acidic Releases an H+ ion when the H+ concentration decreases

Neutralization Reaction When strong bases and acids are combined the result is to make an ionic compound and water – the pH neutralizes near 7 Examples – Taking Tums and Milk of Magnesia for an upset stomach. These bases “neutralize” the stomach acid by increasing the pH and that makes the discomfort go away.

There are some exceptions: Acidophile – organism that can maintain neutral pH inside its cells while living in an acidic environment of less than pH 2 Includes some bacteria, fungi and algae

Lactose acidophilus A bacteria that lives in the human intestines which contains fluid of pH 2 Considered a “good bacteria” because it produces a digestive enzyme called lactase that breaks down milk sugar and also produces Vitamin K

Parietal Cells Specialized cells in stomach lining that make HCl “stomach acid” - pH 1

Azalea and Rhododendron Plants Need acidic soil of pH 4.5 to bloom

Effect of soil pH on Hydrangea flowers Alkaline soil pH makes them pink

Effect of soil pH on Hydrangea flowers Acidic soil makes hydrangeas blue

Acid Mine Drainage

Cause of acid mine drainage

Acid Mine Drainage

Naturally occurring limestone rock buffers or neutralizes the acidic water

Acid Precipitation

How much stronger is pH at each step 10X pH 2 Is 100X stronger than pH 4

Two Types of Scientific Tests Qualitative Test – test “quality” using our senses – something we observe ex. Litmus test *Quantitative Test – test “quantity” provides an amount or value Ex. pH paper, pH checker

Lab Reminders Reader/Writer’s job – Read and Write That’s It! Reader/Writer has enough to do communicating the lab directions, managing everyone to get things done efficiently, and recording data and conclusions ALWAYS check off the materials list before beginning lab to ensure you have everything Wear your goggles until you check out Check off materials to make sure all equipment is available for next group before asking to check out

pH is a limiting factor

Acids – PUT ANSWERS TO 2.2 B here

Compound that release hydroxide ions or remove hydrogen ions OH- 7 up to 14 but not including 7 Neutral they don’t add H+ or OH- H+ = OH-