Chapter 4.1 - Introducing Acids and Bases Flashcards
What are ACIDS?
According to the Bronstead-Lowry Theory, An Acid is a substance capable of donating a Hydrogen ion/Proton
What is Acidity?
The concentration of H3O+ ions in an aqueous solution.
- Measured on a pH scale.
What is a BASE?
According to Bronstead-Lowry theory, a substance capable of accepting a proton/Hydrogen ion.
Hydrochloric Acid
Formula
Uses
HCl
- Stomach acid to help breakdown proteins
- cleaning agent for brickwork
Sulfuric Acid
Formula
Uses
H2SO4
- chemical manufactured for Car batteries, fertilizers, detergents.
Nitric Acid
Formula
Uses
HNO3
- fertilizers, dyes, and explosives
ETHANOIC/ ACETIC ACID
Formula
Uses
CH3COOH
- vinegar, used as a preservative
Carbonic Acid
Formula
Uses
H2CO3
-soft drinks and beer
Phosphoric Acid
Formula
Uses
H3PO4
- soft drinks and manufacture of fertilizers
Citric Acid
Formula
Uses
C6H8O6
- found in citrus fruits
Ascorbic Acid
Formula
Uses
C6H8O6
- citrus fruits (VITAMIN C)
What is an ALKALI?
A soluble base
- base definition also
What is a solution?
A homogenous mixture of a solute dissolved in a solvent
Sodium hydroxide (Caustic Soda)
Formula
Uses
NaOH
Used in drain and oven cleaners,
Soap making
Ammonia
Formula
Uses
NH3
Used in Household cleaners, fertilizers and explosives
Calcium Hydroxide
Formula
Uses
Ca(OH)2
Found in Cement and mortar
Used in garden lime to adjust soil pH
Magnesium Hydroxide
Formula
Uses
Mg(OH)2
Ingredient In ANTACID, EG MILK OF MAGNESIA to overcome indigestion
Sodium Carbonate
Formula
Uses
Na2CO3
manufacture washing powder and glass
What are some common properties of all ACIDS? (6)
- Turns litmus paper red
- Tend to be CORROSIVE
- SOUR TASTE
- REACTS with BASES: neutralization may occur
- Solutions have relatively low pH
- Solutions CONDUCT ELECTRIC CURRENT
What are some common properties for all BASES?
- Turns Litmus paper blue
- are Caustic and FEEL Slippery
- Tastes Bitter
- Reacts with Acids
- Solutions have relatively high pH
- Solutions conduct an electric current
Why do bases feel slippery?
Bases feel slippery/soapy.
This is because they dissolve the fatty acids and oils from your skin and this cuts down on the friction between your fingers as you rub them together.
Good for cleaning products because they react with fats and oils to produce water-soluble soaps
Explain the Bronsted-Lowry theory
This theory explains that a substance behaves as an ACID WHEN IT DONATES PROTON (H+) to a base.
A substance behaves like a BASE when it ACCEPTS A PROTON from an Acid.
What is an Acid-Base reaction?
An acid-base reaction involves an exchange of protons from an acid to a base.
eg. HCl(g) + H2O(l) –> H3O+ (aq) + Cl- (aq)
Explain the acid-base reaction.
eg. HCl(g) + H2O(l) –> H3O+ (aq) + Cl- (aq)
ACID? BASE? REACTION EQUATIONS
- In an Aqueous solution of Hydrogen chloride, nearly all the hydrogen chloride is present as ions – virtually no molecules of hydrogen chloride remain.
- - This solution is known as Hydrochloric acid. - The HCl molecule has donated a proton to the water molecule, forming the HYDRONIUM ION (H3O+ (aq))
- HCl has acted as the Acid
- Water is the base then, - The hydronium ion can be represented as either H3O+ (aq) or H+ (aq).
Therefore can be represented as either a Hydrolysis reaction
HCl(g) + H2O (L) —> H3O+ (aq) + Cl - (aq)
or a DISSOCIATION REACTION.
HCL (g) —> H+ (aq) Cl- (aq)
Dissociate vs Ionise?
- Ionisation is the process that involves the formation of ions
- Ionisation involves the creation of charges across the participating species
- become charged - dissociation is the process of breaking up a molecule into its constituent atoms, molecules, and ions.
- dissociation occurs due to a weak bond between species.
- breakup
What is Hydrolysis?
A reaction involving the breaking of a bond in a molecule using water as a reactant.
2 smaller molecules are usually formed
What is a Hydrolysis Reaction?
A reaction that occurs when a molecule or ion in an aqueous solution reacts with water, either accepting or donating a proton.
What are the Advantages of the Bronstead-Lowry model?
- Acids and bases are not restricted to aqueous solutions.
eg. a reaction between gases can be an acid-base reaction. - Because it categorized acid-base reactions in the case of proton transfer.
example : solutions HCl (aq) +NH3 (aq) ---> NH4+ (aq) + Cl- (aq) gases HCl (g) + NH3 (g) ---> NH4Cl (s)
What are the limitations of the Bronstead-Lowry Model?
- It cannot be applied to the reaction between acidic and basic oxides.
under certain conditions solid calcium oxide, a basic oxide reacts with gaseous carbon dioxide, an acidic oxide to produce calcium carbonate salt.
CaO (s) + CO2 (g) —> CaCO3 (s)
What are conjugate acid-base pairs?
What are Conjugate acids and bases?
Conjugate acid-base pairs are molecules that differ from each other by an H+ ion.
(on other side of the equation)
When a conjugate acid donates a proton, it forms a conjugate base.
When a base accepts a proton, it forms a conjugate acid.
How can the proton/hydrogen ion affect acidity of a solution be represented?
A proton or hydrogen ion in a solution can be represented by the hydronium ion, H3O+ (aq), or simply as H+ (aq)
What are Amphiprotic substances?
Example?
They are substances that act as either acids or bases, depending on the substance with which they are reacting.
example WATER - can act as a base or acid depending on the solute present.
- if the SOLUTE is STRONGER ACID than water, then the WATER will act as a BASE.
- if the SOLUTE is a STRONGER BASE than Water, then the WATER will act as an ACID.
Although both reactions are possible for all amphiprotic substances in water, generally one reaction dominates.
Examples of Amphiprotic substances
H2O HCO3- H2PO4- HPO4 (-2) HSO4 -
How to determine the dominant amphiprotic reaction?
The dominant reaction can be identified by measuring the pH
- A measure of the amount of hydronium ion in solution.
What are monoprotic acids?
Examples?
Acids that can donate ONLY ONE proton per molecule.
- only the hydrogen part of the highly polar O-H bond is donated
- The hydrogen atom is called the ACIDIC PROTON
HCl
HF (hydrofluoric acid)
HNO3
CH3COOH
What is a polyprotic acid?
An acid that can donate more than 1 proton to a base.
- the number of hydrogen ions an acid can donate depends on the structure of the acid
- they do not donate all at once but does so in steps when reacting with a base
- Diprotic donates 2
- Triprotic donates 3
Example of Diprotic acids
- Sulfuric Acid - H2SO4
2. Carbonic Acid - H2CO4
What are the stages a diprotic acid, such as sulfuric acid ionizes?
2 stages
stage 1 : H2SO4 (L) + H2O (L) —-> HSO4- (aq) + H3O+ (aq)
Stage 2 : HSO4- (aq) + H2O (L) SO4 (-2) (aq) + H3O+ (aq)
Examples of triprotic acids
- PHOSPHORIC ACID - H3PO4
2. BORIC ACID (H3BO3)
How do triprotic acids ionize?
3 stages
- the extent of ionization decreases progressively from stages 1 to 3.
stage 1 : H3PO4 (aq) + H2O (L) H2PO4 - (aq) + H3O+ (aq)
stage 2: H2PO4 (-2) - (aq) + H2O (L) HPO4 (-2) (aq) + H3O+ (aq)
stage 3: HPO4 (-3) (aq) + H2O (L) PO4 (-3) + H3O+ (aq)
