Chemistry 121/122 Acids, Bases and Salts. Properties of Acids Acids, in foods, give a sour or tart...
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Chemistry 121/122 Acids, Bases and Salts. Properties of Acids Acids, in foods, give a sour or tart taste Aqueous solutions of acids are electrolytes (conduct
Properties of Acids Acids, in foods, give a sour or tart taste
Aqueous solutions of acids are electrolytes (conduct electricity
(release ions in solution) Acids can be either strong or weak
electrolytes May cause indicators to change colour Acids can react
with metals to produce hydrogen gas (H 2 ) Acids can react with
bases to form water and a salt Acids can also react with hydrogen
carbonates to produce carbon dioxide, water and a salt
Slide 3
Properties of Bases Most of the time, we do not eat anything
basic - they are too bitter (soap) They can be compared to acids by
their properties They are electrolytes that can change the colour
of an indicator They feel slippery when wet When a base that
contains hydroxide reacts with an acid, water and a salt form
Slide 4
Arrhenius Acids and Bases Although not entirely comprehensive,
Arrhenius was one of the first scientists to propose general rules
for acids and bases He proposed acids to be those substances that
produced H + in solution (dissolved in water) Bases were substances
that produced OH - ions in solution (dissolved in water)
Slide 5
Arrhenius Acids When one hydrogen ionizes in solution, the acid
is said to be monoprotic (HCl) Two hydrogen ions = diprotic (H 2 SO
4 ) Three H + = triprotic (H 3 PO 4 ) We now know that not all
acids release hydrogen ions in solution Only hydrogen involved in
strong polar bonds (large differences in electronegativities) with
an anion will ionize
Slide 6
Difference between strong and weak bonds A strong acid (HCl)
ionizes completely HCl (aq) H + (aq) + Cl - (aq) EN difference =
1.0 Even though a substance contains hydrogen, it may not be
considered an acid if it does not ionize due to weak covalent bonds
CH 4(g) = EN difference = 0.3
Slide 7
Arrhenius Bases Group 1 metals react with water to produce
solutions that are basic Ex. Na + H 2 O NaOH + H 2 -the sodium
hydroxide produced is basic -it is very soluble in water -as a
result, in solution, it dissociates to form Na + and OH - -There
are strong bases and weak bases due to differences in
solubility
Slide 8
Practice 1. Write balanced equations for the reactions between
the following: a.Aluminum and sulfuric acid b.Caclium carbonate and
hydrobromic acid (metal carbonates produce water and carbon dioxide
as products) 2. Write the net ionic equation for the reaction in
question 1. (b)
Slide 9
Bronsted-Lowry Acids and Bases The definition of an Arrhenius
acid and base does not include all acids and bases Bronsted-Lowry
attempts to be more comprehensive Acids are defined as a H + donor
and bases are H + acceptors Ex. Ammonia (NH 3 ) accepts a H + to
form ammonium (NH 4 + ), so is a base
Slide 10
Conjugate Acids and Bases The particle formed by accepting the
H + is called the conjugate acid Conversely, the particle that
remains once the acid has donated a H + is called the conjugate
base Ex. NH 3 + H 2 O NH 4 + + OH - NH 3 = base (accepts H+), H 2 O
= acid (donates H+), NH 4 + = conjugate acid (gains H+), OH - =
conjugate base (loses H+). Together, a conjugate acid-base pair
forms two substances linked by a single H +
Slide 11
Hydronium Ion (H 3 O + ) When water gains a hydrogen ion, it
becomes positively charged H 2 SO 4 + H 2 O H 3 O + + HSO 4 -
However, water does not always do this Sometimes, it acts as an
acid, donating H + instead of gaining
Slide 12
Practice 1. Identify the conjugate acid-base pairs in each
reaction. a. NH 4 + (aq) + OH - (aq) NH 3(aq) + H 2 O (l) b. HBr
(aq) + H 2 O (l) H 3 O + (aq) + Br - (aq) c. CO 3 2- (aq) + H 2 O
(l) HCO - (aq) + OH - (aq) 2. The products of an acid-base reaction
are H 3 O + and SO 4 2-. Write a balanced equation for the reaction
and identify the conjugate acid-base pairs.
Slide 13
Lewis Acids and Bases As an extension of his theory using
electron dot diagrams, Lewis proposed that acids are electron pair
acceptors and bases were electron pair donors Such electrons are
used to create covalent bonds between two atoms H + can accept
electron pairs so it can be classified as a Lewis acid
Slide 14
For the remainder of class Identify each reactant as an acid or
base. Which definition should you use to help with your
classification? a.KOH + HBr KBr + H 2 O b.HCl + H 2 O H 3 O + + Cl
- Q. 1-8, p. 593 Guided Reading for section 19.1