Acids And Alkalis Flashcards
1
Q
The pH scale
A
A scale ranging from about 0-14, telling you how acidic or alkaline a solution is.
2
Q
What pH is a strong acid?
A
1-3 (Red)
3
Q
What pH is a weak acid?
A
4-6 (orange, yellow and light green)
4
Q
What pH is neutral?
A
7 (Green)
5
Q
What pH is weak alkali?
A
8-10 (Green to blue)
6
Q
What pH is strong alkali?
A
11-14 (Dark blue to purple)
7
Q
Acids have a pH of less than…
A
6
8
Q
Examples of acids
A
Nitric acid, sulfuric acid, hydrochloric acid, carbolic acid, phosphoric acid (coca cola), citric acid (eg. lemons)
9
Q
Bases have a pH of more than…
A
8
10
Q
Examples of bases
A
Sodium hydroxide, copper oxide, potassium hydroxide, ammonia
11
Q
What is calcium hydroxide?
A
Limewater
12
Q
What is litmus paper?
A
It is filter paper soaked in litmus solution and dried, and it is best to test gases.
13
Q
Name all the indicators
A
- Red litmus solution
- Blue litmus solution
- Phenolphthalein solution
- Methyl orange solution
- Universal indicator solution
14
Q
Red litmus solution
A
Acid: Stays red
Neutral: Stays red
Alkali: Goes blue
15
Q
Blue litmus solution
A
Acid: Goes red
Neutral: Stays blue
Alkali: Stays blue
16
Q
Phenolphthalein solution
A
Acid: Stays colourless
Neutral: Stays colourless
Alkali: Goes bright pink
17
Q
Methyl Orange solution
A
Acid: Goes red
Neutral: Stays orange
Alkali: Goes yellow
18
Q
Universal indicator solution
A
Acid: Goes red/yellow/orange
Neutral: Goes green
Alkali: Goes blue/purple
19
Q
Testing with litmus solution is better in a…
A
Solid and liquid, but not gases
20
Q
What is toothpaste or baking powder?
A
Alkali
21
Q
Bromothymol Blue
A
- used for testing pH, and testing photosynthesis and respiration
- similar colour change to UI
- yellow at low pH, and blue at high pH
22
Q
A
23
Q
Where are indicators used in the world?
A
- soil-testing kits
- swimming pools are acidic due to chlorine, and can be tested
24
Q
Are alkalis corrosive?
A
Very corrosive
25
Are acids corrosive?
Very corrosive
26
What does vinegar have?
CH(3)COH
27
What state of matter is pure ethanoic acid?
Liquid
28
What state of matter are all acids?
Aqueous
29
What is neutralisation?
The reaction between an acid and a base, where both the acid and base are neutralised and water is formed.
30
An acid is…
A source of hydrogen ions (H(+)) in an aqueous solution. Hence, HCl (hydrochloric acid) contains H(+) ions, as well as H(2)SO(4) (sulfuric acid).
31
What happens when hydrochloric acid splits into ions?
HCl (aq) —> H(+) (aq) + Cl(-) (aq)
When dissolved, the chlorine takes the hydrogen electron, for a full outer shell, and the hydrogen becomes a proton.
32
An alkali is…
A source of hydroxide ions, OH(-) (aq) in an aqueous solution.
NaOH contains OH(-) ions
33
Sodium hydroxide in solution
NaOH (aq) —> OH(-) + Na(+)
34
What is ammonia?
A weak alkali, and a smelly gas
35
Draw ammonia covalently.
N/a
36
Word and chemical equation of ammonia dissolved in water
ammonia + water —> ammonium hydroxide
NH(3) + H(2)O —> NH(4)OH
Ammonium can only be found part of a compound.
37
Explain what happens when ammonia reacts with water.
When ammonia reacts with water, the water donates a hydrogen atom to the ammonia, however, the hydrogen atom leaves behind its electron, forming a hydrogen ion. Hence, ammonia gains a H+ ion, becoming ammonium, and the water loses a hydrogen, with an extra electron, hence it is OH-, forming the compound ammonium hydroxide.
38
Neutralisation ionic equation
H(+) (aq) + OH(-) (aq) —> H2O (l)
39
Draw a hydrogen atom and a hydrogen ion
N/a
40
Why can the hydrogen ion be referred to as a proton?
It loses its electron, and has no neutrons, hence it is a proton.
41
Word and chemical equation of reaction between ammonia and hydrogen chloride
ammonia + hydrogen chloride —> ammonium chloride
NH3 (g) + HCl (g) —> NH4Cl (s)
42
Draw the dot and cross diagram of ammonia and hydrogen chloride reaction
N/a
43
What happens when ammonia reacts with hydrogen chloride?
The hydrogen chloride molecule donates a H(+) ion forming the NH4(+) ion. The ammonia molecule accepts a proton from the hydrogen chloride molecule, forming a chloride ion.
44
Acid 2nd definition
Proton donors
45
Alkali 2nd definition
Proton acceptors
46
Reaction of acids with metals experiment
1. Place about 5cm^3 of hydrochloric acid in a test tube (a depth of about three fingers)
2. Add a small piece of magnesium ribbon
3. If a gas forms, trap some by putting a finger over the end of the tube
4. After a while remove your finger and quickly test the gas with a burning splint
5. Record your observations
Observation: effervescence or fizzing, Mg reacts to gradually disappear, gets warmer
Testing the gas: hydrogen produces squeaky pop
47
Reaction of acid with metal oxide experiment
1. Place about 5cm^3 of hydrochloric acid in a boiling tube (a depth of about two fingers)
2. Add half a spatula measure of black copper oxide
3. Warm the mixture gently for 10 seconds using the heating flame, but DO NOT ALLOW TO BOIL
4. Place boiling tube into a test tube rack and allow to cool
5. Record your observations
Observations: changes colour to green, goes almost colourless, residue at the bottom, vibrates while heating, effervescence
This was a different colour after filtering due to the salt, copper chloride.
48
Reaction of acid with metal hydroxide
1. Place about 2cm^3 of hydrochloric acid in a test tube
2. Add about 2cm^3 of sodium hydroxide to the acid
3. Record your observations
Observations: no visible reaction, test tube gets warmer immediately after, colourless solution, no gas given off shown by lack of effervescence
49
Reaction of acids with metal carbonates
1. Put about 5cm^3 of hydrochloric acid in a boiling tube
2. Add a couple of marble chips (calcium carbonate)
3. If a gas forms, use a delivery tube to bubble the gas through limewater in another test tube
4. Record your observations
Observations: fizzing or effervescence
Testing gas: limewater turns cloudy due to carbon dioxide
50
Acid + Metal —>
Salt + Hydrogen
51
Acid + Metal Oxide (Base) —>
Salt + water
52
Acid + Metal Hydroxide (Base) —>
Salt + water
53
Acid + Metal Carbonate —>
Salt + water + carbon dioxide
54
Hydrochloric acid
HCl
55
Sulphuric acid
H2SO4
56
Nitric acid
HNO3
57
Zinc
Zn(2+)
58
Silver
Ag(+)
59
Lead
Pb(2+)
60
Ammonium
NH4(+)
61
Hydroxide
OH(-)
62
Nitrate
NO3(-)
63
Sulphate
SO4(2-)
64
Carbonate
CO3(2-)
65
Iron (II)
Fe(2+)
66
Iron (III)
Fe(3+)
67
Aluminium
Al(3+)
68
Diatomic molecules
Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine, Iodine
69
Sulphide
S(2-)
70
Chromium
Cr(3+)
71
Nitrate
N(3-)
72
Vanadium
V(2+)
73
Copper
Cu(2+)
74
What state of matter are all ionic salts?
They are all solids, but most are formed in solution, so they may be aqueous, varying based on solubility.
75
Examples of dissolving
1. Oxygen dissolves in water for fish
2. Ethanol dissolves in water to drink
76
What is a salt formed from?
Ionic parts
77
Soluble definition
The ability of a substance to dissolve in a liquid, typically water, or solvent
78
Insoluble definition
The inability of a substance to dissolve in a liquid, typically water for fish
79
Solute definition
The soluble substance that is dissolves in the liquid (solvent) to form a solution
80
Solvent definition
The liquid a solute is dissolved in
81
Solution definition
The combination of a dissolved solute and solvent
82
Solubility definition
A measure of the extent of the ability a substance has to dissolve in a liquid, typically water, in g/100g of solvent
83
What is calcium hydroxide?
Limewater
84
What is calcium carbonate?
Limestone
85
What compounds are always soluble?
Sodium
Nitrate
Ammonium
Potassium
86
Are chlorides soluble?
Yes, except for silver and lead
87
Are sulphates soluble?
Yes, except for barium, calcium and lead
88
Are carbonates soluble?
No, except for sodium, potassium and ammonium, which are soluble
89
Are hydroxides soluble?
No, except for sodium, potassium and calcium (calcium hydroxide is slightly soluble)
90
What metal is not solid?
Mercury
91
What happens if salts are not soluble?
They are solid
92
Burning metals and non-metals in oxygen experiment
1. The substance is ignites with a Bunsen burner
2. The burning substance is placed in a gas jar of oxygen gas and observations made
3. When cool, water was added to the gas jar
4. UI solution was then added and the colour change was noted
93
Draw burning metals and non-metals in oxygen apparatus
N/a
94
Sodium is burnt
Observations when burnt: Orange flame, brighter in oxygen
sodium + oxygen —> sodium oxide
4Na (s) + O2 (g) —> 2Na2O (s)
When UI added to gas jar: UI goes from green to blue, alkali, dissolves a little bit in water
95
Magnesium is burnt
Caution: Must use glass filter to look at the reaction, as it is so bright
Observation while burnt: Very bright white flame in oxygen
magnesium + oxygen —> magnesium oxide
2Mg (s) + O2 (g) —> 2MgO (s)
Observations when UI is added: UI goes from green to blue, alkali, dissolves a bit in water
Dissolve reaction:
MgO + H2O —> Mg(OH)2
96
Sulphur is burnt
Observations when burnt: blue flame, brighter in oxygen, sulphur melts
Caution: Sulphur dioxide is a smelly, colourless gas, that is quite harmful
sulphur + oxygen —> sulphur dioxide
S (s) + O2 (g) —> SO2 (g)
Observations when UI added: goes from green to red, acid, purple flame in
97
Carbon is burnt
Observations when burnt: black solid ignites, sparks and orange bits appear, orange flame burns a lot brighter in oxygen
carbon + oxygen —> carbon dioxide
C (s) + O2 (g) —> CO2 (g)
Observations when UI added: goes from green to red, acid
98
What happens when non-metals burn in oxygen?
- non-metal oxides form
- UI turns green to red
- acidic solutions
99
What happens when metals burn in oxygen?
- metal oxides form
- UI goes from green to blue
- alkaline solution forms
