Chapter 17 - ACIDS AND BASES Flashcards
(69 cards)
1
Q
Define Acid
A
A substance capable of producing hydrogen ions (H+) in solution
(Arrhenius Model)
Or Donating a hydrogen ions (Brønsted-Lowry Model)
2
Q
Define Base
A
A substance capable of producing hydroxide ions (OH-) in solution (Arrhenius Model)
Or accepts a proton (Brønsted-Lowry Model)
3
Q
Define Acidity
A
Acidity is the concentration of H+ ions in an aqueous solution.
Acidity is measured using the pH scale
4
Q
Hydrochloric Acid formula and use
A
HCl
*Stomach Acid
5
Q
Nitric Acid Formula and use
A
HNO3
- manufacture of fertilisers, Dyes and explosives
6
Q
Sulphuric Acid Formula and use
A
H2SO4
*Car batteries, manufacturing of detergent and fertiliser
7
Q
Carbonic Acid Formula and use
A
H2CO3
*carbonated soft drinks
8
Q
Phosphoric Acid Formula and use
A
H3PO4
*some soft drinks and manufacture of fertiliser
9
Q
Citric Acid Formula and use
A
C6H10O7
*juice of citric fruits Eg lemons
10
Q
Ascorbic Acid Formula and use
A
H8C6O6
*found in Citrus fruits (vitamin C)
11
Q
Potassium Hydroxide Formula
A
KOH
12
Q
Sodium Hydroxide Formula and use
A
Na(OH)2
- Used in drain and oven cleaners, soap making
13
Q
Ammonia (base) formula and use
A
NH3
Used in household cleaners, fertilisers and explosives
14
Q
Sodium Carbonate formula
A
NaCO3
15
Q
Magnesium Hydroxide
A
Mg(OH)2
16
Q
What is an Alkali?
A
A soluble base is called an alkali
17
Q
Formula of Calcium hydroxide and use
A
Ca(OH)2
- found in cement and mortar, used in garden lime to adjust pH of soil
18
Q
Formula of Ethanoic Acid/ Aecetic Acid and use
A
CH3COOH
*a component in vinegar
19
Q
What are some properties of an Acid?
A
- Turns litmus paper Red
- Tends to be Corrosive
- Tends to taste sour
- Reacts with Bases (and neutralisation occurs)
- Relatively low pH (0-7)
- Conducts and Electric Current in solution
20
Q
What the properties of a base?
A
- Turns litmus paper blue
- Tends to be Caustic (corrosive for a Base) and SLIPPERY
- Tends to taste Bitter
- Reacts with Acids (and neutralisation occurs)
- Conducts an electric current in solution
21
Q
Why are Bases effective cleaners? Main components in a cleaning product.
A
They react with FATS or OILS to produce water soluble soaps
Body excretes acid products therefore base will neutralise the environment cleaning
22
Q
Why are Bases slippery?
A
Bases are slippery because they react with Fats on skin to produce a soap
23
Q
What is litmus paper?
A
- Litmus is a water-soluble mixture of different dyes extracted from lichens.
- It is often adsorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity
24
Q
What is an Indicator?
A
Indicators are chemicals that change colour, depend on the acidity of the solution.
Eg plant extracts, Litmus in litmus paper, Cabbage, Rose petals and blackberries
25
What is a Universal Indicator?
A universal indicator is a pH indicator made of a solution of several compounds that exhibits several smooth colour changes over a wide range pH values to indicate the acidity or alkalinity of solutions.
**Colours shown on the universal indicator can be used to determine the approximate pH of solutions
26
What is a pH scale?
pH is a scale used to SPECIFY THE ACIDITY OR BASICITY OF AN AQUEOUS SOLUTION
At room temp (25°C) pure water is a pH of 7
Defined in terms of 25°C
Acid = pH of 0-7
Base = pH of 7-14
Negative logarithm
- as the pH of a DECREASES the concentration of H+ INCREASES
27
What is ionisation
Ionisation is
- process that involves the formation of ions VIA the removal of one or more electrons from an atom or ion
- the reaction of a molecular substance with a solvent to form ions in solution
28
What is Dissociation?
- Takes place in ionic compounds where ions are present
- it is the process if breaking up a compound in a Polar solvent into its constituent atoms, molecules or ions
- due to weak ion- dipole bonds between the species and strong H bonds
29
What is the Arrhenius Model? For Acids
It is a model that defines an acid as a substance that ionises water to produce H+
It is useful because it explains the similarities in the reactions of different acids.
The hydrogen ion that are present in acid solutions account for the common properties of acids.
30
What is a Hydronium ion?
H3O+
In water, the H+ ion exists as an Hydronium ion
31
How Arrhenius model Acid reactions be written?
HCl (s)————> H+ (aq) + Cl- (aq)
H2O (l)
Or
HCl(s) +H2O(l) ——> H3O+ (aq) + Cl- (aq)
32
What are Polyprotic Acids?
Polyprotic Acid is an acid molecule that generates more than one hydrogen ion when ionised in water.
33
What is a monotropic Acid?
An acid molecule that generates only 1 hydrogen ion when ionised in water.
Eg Ethanoic Acid (acetic) CH3COOH contains 4 hydrogens but only 1 hydrogen ion forms
- ONLY THW ONE HYDROGEN THAT IS PART OF THE HIGHLY POLAR (O-H) BOND IS IONISED IN WATER.
34
What is Diprotic acid
An acid that can ionised in water to form 2 x H+ ions
Eg. Sulphuric Acid - H2SO4
Carbonic Acid - H2CO3
Equation
H2SO4 ————> SO4-2(aq) +2H+ (aq)
H2O (l)
35
What is Triprotic acids
An acid molecule that generates 3 hydronium ions when ionised in water
Eg Phosphoric Acid - H3PO4
BORIC ACID - H3BO3
Equation
H3PO4 (aq) Po4^3- (aq) + 3H+(aq)
H2O (l)
36
How are H ions made in solution?
In general, hydrogen atoms bonded to a highly electronegative atom, thus forming polar bonds- are ionised in solution. (H+)
Certain bonds between a hydrogen atom attached to an electrons give oxygen atom broken when these molecules ionised in water
See the drawing
37
What is the Arrhenius Model? For bases
A base as a substance that dissociated in water to produce OH- ions
- the presence of the hydroxide ions in solutions of basses accounts for the common properties of bases
Equation
NaOH (s) —-> Na+ (aq) + OH - (aq)
Some bases dissociate to from more than one hydroxide ion
Ca(OH)2 (s) —-> Ca+2 (aq) +2OH- (aq)
38
What are electrolytes?
An electrolyte is a substance that produces an electrically conducting solution when dissolved in a polar solvent, such as water.
The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. Electrically, such a solution is neutral.
39
Why are Acids and Bases Electrolytes?
According ti Arrhenius model, acids ionise in water to produce H+ ions, while Bases ionise in water to produce OH- ions.
THE PRODUCTION OF THESE CHARGED PARTICLES IN SOLUTION ALLOWS ACIDS AND BASES TO CONDUCT ELECTRICITY.
THE FLOW OF THE CURRENT IN THE SOLUTION IS A RESUKT OF THE MOVEMENT OF THESE IONS
40
What are neutralisation reactions?
Acid - base reactions which produce a salt and water
- the pH is moved closer to 7
- the combination of all OH - ions and all H+ ions react to produce water
Eg Antacid + HCl - Salt + H2O (sometimes CO2 - depending of type of base in antacids)
41
What are some limitations of the Arrhenius Model of Acids as Bases?
It explains the properties of an acids in terms if the formation of hydrogen ions by IONISATION of the acid molecule.
Limitations
1. Does NOT EXPLAIN WHY some SUBSTANCES WHICH DO NOT CONTAIN HYDROGEN FORM ACIDIC SOLUTIONS WHEN MIXED WITH WATER.
Eg. An acidic solution is formed when CO2 or SO2 is dissolved in water
2. Does not explain why some substances such as AMMONIA (NH3) or SODIUM HYDROGEN CARBONATE (NaHCO3) FORM BASIC SOLUTIONS WHEN MIXED WITH WATER EVEN THOUGH THEY DO NOT CONTAIN (OH-) ions
3. RESTRICTED TO ACIDS AND BASES THAT DISSOLVE IN WATER.
- model does not explain acid-base behaviour in non-aqueous solutions
42
What is the new and improved acid-base model?
Brønsted-Lowry model which describes an acid as a substance that can donate H+ (proton) to a base, which accepts the proton.
Vice versa but with a (OH-)
43
What are some strong acids?
Hydrochloric Acid - HCl
Sulfuric Acid - H2SO4
Nitric Acid - HNO3
44
What are some weak acids?
Ethanoic/ acetic Acid - CH3COOH
Carbonic Acid - H2CO3
Phosphoric Acid - H3PO4
45
What are some strong Bases?
Sodium hydroxide - NaOH
Potassium Hydroxide - KOH
Calcium hydroxide - Ca(OH)2
46
What is a weak base?
Ammonia - NH3
47
Why can acid solutions of the same concentration not have the same concentration of H+?
Some acids can be ionised more readily than others, which makes them stronger acids.
Likewise some bases can be ionised more readily than others.
Therefore is due to the composition of the Acid/base
48
What are strong acids?
Acids that are completely ionised are called strong acids.
Therefore, solutions of strong acids contain ions, with virtually no unreacted Acid molecules remaining.
One arrow rep.
49
What are weak acids?
Represented by reverse arrows
Weak acid = an acid that is partly ionised in water
50
What is a weak base?
A base that is partially dissociates in water to produce OH- ions
Reverse arrows
51
What is a strong base?
A base that complete ionises in aqueous solution
52
What is a super acid?
Super aids are acids that have acidity greater than the acidity of pure sulfuric acid.
Eg Fulrosulfuric Acid
Has similar geometry to the sulfuric Acid molecule
The highly electronegative fluorine atom causes the oxygen -hydrogen bond in the fluorosulfuric acid to be more polarised than the O-H bond is H2SO4
The acidic proton is easily transferred to a base
Used in the production of plastics and high-octane petrol, coal gasification and in research
Others include
- CF3CO3H trifilic Acid
- (H(CHB11Cl11)) Carborane Acid
- H2FSbF6 fluoroantimonic Acid (strongest) 10^16
53
Strength versus Concentration
- concentration and dilute describe the amount of acid or base dissolved in a given volume of solution
- Concentration refers to the number of moles per volume are contained within the solution.
- It also applies to how much of the acid or base is contained within the solution.
- The strength of an acid or base refers to how much of the acid or bases ions are released in a solution.
54
Calculation to find the pH of a solution
pH = -log[H+]
55
Calculation to Find the H+ ions in a solution
[H+] = 10^(-pH)
56
pH 2 vs pH 3
A solution with pH 2 has 10x more concentration of Hydrogen ions as one of pH 3
57
What is a Salt?
Salt is a general name given to an ionic compounds.
Therefore formed from a positive metal cation and a negative non-metal anion.
Salts are formed formed often from reactions involving acids and bases
58
What are spectator ions?
Ions that are dissolved in the solution and are present as ions present before and after the reaction, but are not involved in the reaction.
Omitted from ionic equation.
59
Ionic equation
Ions + ions —> salt
Or salt —> ion + ion
** the reaction only
60
Net ionic equation
Write completed equation
Separate each to individual ions
Then the things that remain the same (same state) are omitted
Then the net ionic equation is written
61
What is neutralised?
make (an acidic or alkaline substance) chemically neutral.
pH approx 7
62
Reaction between acid and base
Acid + Base —> Salt + Water
63
Reaction between Acid and metal
Acid + metal —> H2 + Salt
64
Reaction between Acid + Bi/ Carbonate or Hydrogen carbonate
Acid + Bi/Carbonate —> Salt + water + CO2
65
Reaction between Acid + metal sulfite
Acid + metal sulfite —> salt + Sulfur dioxide ( pungent choking gas - SO2) + water
66
Reaction between ammonium salt and base
Ammonium salt + Base —> salt + ammonia + water
NH4+ salt
And ammonia = NH3
67
What happens during dilution?
- Amounts of acid or base in solution DOES NOT CHANGE
- Volume of the solution increases and its concentration decreases
- pH increases as solution of an acid is diluted
- pH decreases when solution of a base is diluted
68
Main workings for finding quantity of other reactants and products
1. Write a balanced equation for reaction
2. Calculate the amount (in moles) of given substance
3. Use the mole ratios of reactants and products in the balanced chemical equation to calculate the amount (in mol) of required substance
4. Convert amount (in mol) of the required substances to units of question.
69
How to calculate a diluted acid?
1. Find concentration
2. The concentration of H+ ions
3. pH log formula
