ACIDS AND BASES

Atoms vs. Molecules Give some examples of molecules Water (H 2 O) Carbon dioxide (CO 2 ) Give some examples of atoms Hydrogen (H) Oxygen (O) Carbon (C) Atoms are the smallest particle of an element that still have the same properties as the element.

How are atoms and molecules related? Molecules are made up of atoms chemically bonded together. Individual atoms and molecules are too small to be seen!

Subatomic Particles Subatomic particles are particles that are smaller than atoms, and are found in atoms. There are 3 different subatomic particles: Protons Positive charge/found in the atom’s nucleus Neutrons Neutral (no charge)/found in the atom’s nucleus Electrons Negative charge/found outside the atom’s nucleus

Atoms usually have an equal number of protons (+) and electrons (-) and are electrically neutral. Atoms can gain or lose electrons and are called ions. Atoms that lose electrons (-) develop a positive charge. → gain electrons (-) develop a negative charge. → ● # Electrons(-) = # Protons(+) 6 Electrons(-) 7 Protons(+) ● ● # Electrons(-) = # Protons(+)8 Electrons(-) 7 Protons(+)

HYDROGEN ATOMS Hydrogen atoms have one proton and one electron. When a hydrogen atom loses its electron, it becomes a hydrogen ion and is symbolized as H +.

WATER Formula: H 2 OPicture: A water molecule is made up of two hydrogen atoms, and one oxygen atoms.

Water molecules can dissociate (split into ions): H 2 O  H + + OH - Hydrogen ion + Hydroxide ion The electron (-) from one of the hydrogen (H) atoms stays with the OH when the water molecule dissociates. For every one H + there is one OH -.

Acids and Bases Water can dissociate- separate into ions. H 2 O  H + + OH - (missing e - )(extra e - ) H + =Hydrogen ion OH - =Hydroxide ion The H + can then combine with another water molecule H + + H 2 O  H 3 O + to make an Hydronium ion- H 3 O +

So we can say that water [ H + ] = [OH - ] Or [H3O + ] = {OH - ] [concentration of] H 2 O H + OH - H 3 O +

ACIDS Contain hydrogen (in their formula) Contain hydrogen ions (H+), hydrogen atoms with a positive charge, that combine with nonmetallic elements or ions. React with metals to produce hydrogen gas Can be dangerous/corrosive Those that are safe to taste, taste sour Do not feel slippery

Examples of some Acids: Acetic acid HC 2 H 3 O 2 Boric Acid H 3 BO 3 Carbonic Acid H 2 CO 3 Hydrochloric acid, HCl Sulfuric acid, H 2 SO 4 Citric acid H 2 C 6 H 5 O 7 (C 6 H 7 O 8 ) Nitric acid HNO 3 Phosphoric acid H 3 PO 4 Common examples/Uses: Ascorbic Acid = Vitamin C Acetic Acid = Vinegar Carbonic Acid = Carbonated Beverages Citric Acid = in Citrus Fruit Hydrochloric Acid = Stomach Acid

When an acid is mixed with water it dissociates(splits into ions). HCl+ H 2 O H + Cl - +H 2 O We can say that acids give off H + or increase the concentration of H +

BASES Contain hydrogen and oxygen (OH) (in their formula) Produce hydrogen and oxygen combined into a hydroxide ion (OH - ) Are formed and hydroxide ions (OH - ) are released when some nonmetals are placed in water Can be dangerous chemicals/corrosive Those that are safe to taste, taste bitter Feel slippery

Examples of some Bases: Magnesium Hydroxide Mg(OH) 2 Calcium Hydroxide Ca(OH) 2 Sodium Hydroxide NaOH Ammonium Hydroxide NH 4 OH Ammonia NH 3 Common Examples /Uses: Antacids Cleaners

When a base is mixed with water it dissociates(splits into ions). KOH + H 2 O K + + OH - We can say that bases: Give off OH - or Increase the amount of OH - (substances that accept (decrease) the amount of H + are considered bases also) (NH 3 + H + → NH 4 + )

MEASURING THE STRENGTH OF ACIDS AND BASES The pH scale is used to measure the strength of acid and bases. Compares the [H + ] to the concentration of [OH - ]. [H + ] [H 3 O + ] > [OH - ] [H + ]=[OH - ] [OH - ]>[H + ][H 3 O + ] [OH - ] < [H + ][H 3 O + ] [H + ] [H 3 O + ] < [OH - ] Acid Neutral Base More H 3 O + More OH - Less OH - Less H 3 O +

(H + ) Acid Neutral Base (OH + ) Every unit on the pH scale is a Ten times change in (H + /OH - ) Comparing Solutions: pH 3 vs. pH 7 pH 3 solution has more H + by a factor of 10 5 (10 x 10 x 10 x 10 x 10) 100,000 times more H + pH 3 solution has less OH - by a factor of 10 5 (10 x 10 x 10 x 10 x 10) 100,000 times less OH - pH 12 vs. pH 5 pH 12 has more OH - less H + by 10 7 T IMES pH 5 has more H + less OH - by 10 7 T IMES

NEUTRALIZATION When acids are mixed with bases they neutralize each other. The pH of the mixture will be somewhere between the pH of the acid and the pH of the base. Mixing a strong acid (pH= 2) with a strong base (pH=12) will result in a pH of about 7. ( ÷ 2) Mixing a weak acid (pH= 6) with a weak base (pH=8) will result in a pH of about 7. (6 + 8 ÷ 2) Mixing a strong acid (pH= 2) with a weak base (pH=8) will result in a pH of about 6. ( ÷ 2) Mixing a weak acid (pH= 6) with a strong base (pH=10) will result in a pH of about 8. ( ÷ 2)

INDICATORS Substances (solids, liquids) that can be used to determine if something is acidic or basic (alkaline). Indicators change color depending on the acidity of the solution. Have we used any indicators this year in lab? Phenolphthalein and red litmus paper

INDICATORS Liquids Bromthymol Blue………… Phenolphthalein…………. Phenol Red………………….. Universal…………………….. Paper Blue Litmus…………………. Red Litmus………………….. pH paper……………………… in Acidin Base YellowBlue ColorlessPink YellowRed R O Y G B I V RedBlue R O Y G B I V Color

Water can act as an acid or a base….. HCl + H 2 O →H 3 O + + Cl - Water is acting as a base by accepting a H +. NH3 + H 2 O → NH OH - Water is acting as an acid by donating an H +.