CELL COMPOUNDS Water Acids, Bases & Buffers Water Acids, Bases & Buffers.
What are we going to discuss? Tables K and L in the Reference Tables list a few of the most common...
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Transcript of What are we going to discuss? Tables K and L in the Reference Tables list a few of the most common...
What are we going to discuss? Tables K and L in the Reference Tables list a few
of the most common Acids and Bases, but what are Acids and Bases.
Acids and Bases have easy to identify properties.
In this unit will learn about these properties, and the important reactions that occur between acids and bases.
Properties of Acids They are electrolytes, that break up into ions in water, that
conduct electricity in aqueous solutions○ Strong acid: good conductor○ Weak acid: poor conductor
Sour Taste
React with most metals to produce H2 (g)
React with bases to form H2O and salt
React with indicators to change colorturn litmus redphenolphthalein turns colorlesspH values are 0.0-6.9see Table M for others
Properties of Bases Electrolytes conduct electricity in aqueous solutions
○ Strong base: good conductor
Bitter Taste
Feel slippery (like soap)
React with acids to form H2O and salt
React with indicators to change colorlitmus turns bluephenolphthalein turns pink pH values are 7.1-14
Arrhenius’ Theory on Acids and Bases
Arrhenius Acid Definition: a substance that ionizes in water to
give hydrogen ions (proton) or a Hydronium ion: H+ or H3O+
Ex: Hydrochloric acid, HCl (a strong acid). HCl (g) H+ (aq) + Cl- (aq)
ACIDIC solutions are formed when an acid transfers a proton to water.
Hydronium Ion
The H+ interacts strongly with a lone pair of electrons on the oxygen of a water molecule. The resulting ion, H3O
+ is
called the hydronium ion.
Ex: HCl + H2O H3O+1 + Cl-1
Arrhenius’ Bases Definition: a substance that ionizes in water to
give hydroxide ions: OH-
Example: NaOH, NH3
NaOH (s) Na+(aq) + OH- (aq)
NH3 + H2O NH4+1 + OH-
SALTS A salt is an ionic compound that does not produce
an H+ ion or OH- ion when dissolved in water.
Salts are not acids or bases they are neutral substances.
Ex. ○ NaCl○ MgCl2
Binary acids –two elements - H+ *
Hydrogen _____ ide Hydrogen chloride Hydrogen fluoride Hydrogen sulfide Hydrogen bromide
Hydro_____ic acid Hydrochloric acid Hydrofluoric acid Hydrosulfuric acid Hydrobromic acid
hydrogen _____ ide becomes hydro_____ic acid
Ternary acids3 elements: H+ and a polyatomic ion
Hydrogen _____ate Hydrogen sulfate Hydrogen chlorate Hydrogen nitrate Hydrogen phosphate
_________ic acid Sulfuric acid chloric acid nitric acid Phosphoric acid
Hydrogen _____ate becomes _________ic acid
Hydrogen ________ite_________ ous acid
Hydrogen _____ite Hydrogen nitrite Hydrogen sulfite Hydrogen chlorite
_______ous acid Nitrous acid Sulfurous acid Chlorous acid
Hydrogen _____ite becomes _______ous acid
Table K and Table L These two tables list the most common acids
and bases.
The top 4 acids on table K are all strong acids while the last 2 are weak acids.
The top 3 bases on table L are strong bases while that last 1 is a weak base.
Strengths of Acids
Strong acids: ionize completely which means if 100 molecules dissolve in water all 100 will break up into ions
Examples:
HCl H+ + Cl-
H2SO4 2H+ + SO4-2
Strengths of Acids Weak acids: ionize slightly or only a
small percentage will break up into ions
Example: acetic acid (vinegar)
CH3COOH CH3COO- + H+
****note if an organic compound ends in COOH it’s a weak acid!!!
Strengths of Bases
Strong bases: ionize completely
Example:
NaOH Na+ +OH-
Strengths of Bases
Weak base: ionizes slightly
Example: ammonia
NH3 + H2O NH4+ + OH-
Acid and Base Reactions
You will need to be familiar with 2 reactions that involve acids and bases.
The first reaction only involves an acid with a metal.
The second reaction deals with reacting an acid with a base to produce a salt and water or neutralization.
Neutralization Reaction
In a neutralization reaction an Acid will react with a base to produce salt and water.
Three ways we can express neutralization reactions:1. Word equation
2. Formula equation
3. Net ionic equation
A net ionic equation has only the ions that have taken part in the reaction. In the reaction the ions that do not change are omitted, these ions are called spectator ions. See example
Neutralization
HCl + NaOH
acid + base water + a salt
HOH + NaCl
Hydrochloric Acid + Sodium Hydroxide yields Water + Sodium Chloride
H+(aq) + Cl-(aq) + Na+
(aq) + OH-(aq) H2O + Na+
(aq) + Cl-(aq)
H+(aq) + OH-
(aq) H2O
This is the net ionic equation for all neutralization reactions this equation shows how the ions are neutralized.
Try This One
H2SO4 + 2NaOH 2H2O + Na2SO4
2H+ + SO4-2 + 2Na+ + 2OH- 2H2O + 2Na+ + SO4
-2
H+ + OH- H2O
Sulfuric acid + sodium hydroxide yields water + sodium sulfate
Concentration of H+ in Acids A. 1.0 M HCl (monoprotic acid)
HCl H+ + Cl-
Produces 1 H+ so the concentration of H+ is 1.0 M
[H+] = 1.0 M
Concentration of H+ in Acids B. 1.0 M H2SO4 (diprotic acid)
H2SO4 2H+ + SO4-2
Produces 2 H+ so the concentration of H+ is 2(1.0 M)
[H+] = 2.0 M
Concentration of OH- in Bases A. 1.0 M KOH
KOH K+ + OH-
Produces 1 OH- so the concentration of OH- is 1.0 M.
[OH-] = 1.0 M
Concentration of OH- in Bases B. 1.0 M NaOH
NaOH Na+ + OH-
Produces 1 OH- so the concentration of OH- is 1.0 M.
[OH-] = 1.0 M
Concentration of OH- in Bases C. 1.0 M Ca(OH)2
Ca(OH)2 Ca+2 + 2OH-
Produces 2 OH- so the concentration of OH- is 2(1.0 M).
[OH-] = 2.0 M
Concentration of OH- in Bases D. 1.0 M Mg(OH)2
Mg(OH)2 Mg+2 + 2OH-
Produces 2 OH- so the concentration of OH- is 2(1.0 M).
[OH-] = 2.0 M
Titration An Acid-Base titration is a lab technique used find
the concentration of an acid or a base by neutralizing it.
During a titration you add volumes of a base to an acid until it is neutralized.
Using the Acid-Base titration formula listed on Table T you can solve for your unknown concentration.
Acid- Base Titrations
MaVa = MbVb (Table T)
Ma = molarity of H+
Va = volume of acid
Mb = molarity of OH-
Vb = volume of base
Titration-Setup
Titrations (Neutralization) Problems Ex. What volume of 0.50M HCl is required to neutralize
100mL of 2.0M NaOH?
MaVa = MbVb
Ma = .5M
Va = ??
Mb = 2.0M
Vb = 100mLPlug in and solve
0.5(x) = 2.0(100)X = 400mL HCl
Try the rest on your own!!!
pH Scale A scale, called the pH scale, has been
developed to express [H+] as a number from 0 to 14.
A pH of 0 is strongly acidic
A pH of 7 is neutral
A pH of 14 is strongly basic
pH Scale
Acid – Base Indicators An indicator is something that changes its color
when it gains or loses a proton or an H+ ion.
There are several different indicators and they change differently when exposed to different pH values.
On your reference tables there is a list of common
indicators that show the color changes at varying pH values.
See Table M You can use multiple indicators to find the
approximate pH of a substance