Acids, Bases, and pH

 Even if you have not studied acids and bases before, you may already know something about them. To tap into this knowledge, identify whether the following are acids or bases. (Hint: Acids and bases have chemical properties that are very different.)  1. Vinegar _____________________________________________________________  2. Baking soda ___________________________________________________________   3. Soap _____________________________________________________________  4. Orange juice ____________________________________________________________  5. Antacid tablets ___________________________________________________________

What is an Acid?  What comes to mind when you hear the word “Acid”?

What is an Acid  An acid is a substance that gives off a hydrogen ion in solution.  In water, acids form what are called hydronium ions

Properties of Acids  Taste Sour  Some can cause burns  Conduct electricity  Change color with an indicator for pH  Corrosive (eats away certain materials).

Why do some acids burn?  Acids form hydrogen ions that have a charge. (H+)  The proteins that make up our bodies also have a charge.  The charge of the ions will pull on the charge of the protein and pull it apart in a process called denaturation !!

Acid Burn

Strong and Weak Acids  All acids ionize when they dissolve in water.  Some acids turn completely into ions, but some acids do not.  Strong acids = completely ionize (turn into ions)  Weak acids = do not completely ionize

What to do if a strong acid gets on you?! 2 ELI5: How and why does acid burn skin? If just burned by a strong acid, would immediately putting a strong base on the area help minimize damage? submitted 2 years ago by connorscomicsconnorscomics 5 comments share

No!!!!

What is a Base?  A base is a compound that forms hydroxide ions (OH-)  They can also be classified as compounds that accept (H+) ions

Properties of a Base  Taste bitter  Feel slippery  Conduct electricity  React with a pH indicator  Corrosive

Weak and Strong Bases.  Just like in acids, bases are classified as weak or strong based on if they ionize completely in water.  Example  NaOH + Water -> Na+ + OH-

What is the pH scale?  pH is derived from the German word (potenz) which means “power” and the chemical symbol H for hydrogen.  Many people think that pH is only a measure of how acidic something is  It actually refers to the concentration of H+ in a solution.

How to Find H+ concentration from pH  Calculate [H+] from a known pH. Find [H+] if pH = 8.5  [H+] = 10 -pH  [H+] =  [H+] = 3.2 x 10-9 M  So if you have a calculator, just take 10 and raise it to the negative pH power, and the number given is the concentration of H+

How to Read the pH Scale  The pH scale ranges from 1-14  On this scale, the lower the number is, the higher the concentration of H+ ions.  If any solution has a pH of 7 it is considered neutral.  The pOH scale is just like the pH scale, but for bases.  On this scale, the lower the number, the higher the OH- concentration

Body and pH  In order for your body to function properly is must maintain a pH between 7 and 7.8  Your body uses enzymes to help run chemical reactions  You don’t want to do to the things running your body

How to not die……

Think About It……..  How is it that you can eat acidic foods on a daily basis and not harm the pH balance of the body?

Buffers  Buffers are solutions containing ions that react with additional acids or bases to minimize their effects of pH.  Blood contains the buffer bicarbonate (HCO 3 -).  Because of this buffer, the body’s pH range will not change drastically.

Questions  What determines if something is a strong acid or base?  What can you do to dilute a solution of strong acid?  Explain the meaning of pH.  Describe the pH values of (9.1, 1.2, and 5.7) as: basic, acidic, or very acidic  Pools need to be between pH.  How would you adjust the pH if you found it was 8.2? What would you do if it was 6.9?

What happens when an Acid meets a Base?  A neutralization is a chemical reaction between an acid and a base that takes place in a water solution. This usually ends in water and a salt!!

Think about…water is neutral  The donated H combines with water to form hydronium, and the donated OH from the base then combines back into 2 units of water.

Making a salt.  A salt is formed when a negative ion left from the acid combines with the positive ion left from the base.  This usually happens at the same time as a neutralization.

Handling an Upset Stomach  Stomach acid: HCl  Antacid :Mg(OH) 2  This is a neutralization reaction so what 2 things will be made?