Acids and bases Flashcards

1
Q

What is an acid?

A
  • an acid is a substance that ionises in water to produce hydrogen ions
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2
Q

What is the definition of basicity of an acid?

A
  • The basicity of an acid is defined as the number of moles of hydrogen ions produced when 1 mole of acid is dissolved in water
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3
Q

What are some examples of monobasic, dibasic and tribasic acids?

A
  • hydrochloric acid (HCl) is monobasic
  • its basicity is 1
  • sulfuric acid (H₂SO₄) is dibasic
  • its basicity is 2
  • phosphoric acid (H3PO4) is tribasic
  • its basicity is 3
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4
Q

What are the properties of acids?

A
  • acids have a sour taste
  • acids dissolve in water to form solutions that conduct electricity
  • acids turn blue litmus red
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5
Q

What is formed when acids react with reactive metals?

A
  • salt
  • hydrogen gas
  • e.g. magnesium + sulfuric acid → magnesium sulfate + hydrogen
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6
Q

Which metals do not react with acids?

A
  • copper
  • mercury
  • silver
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7
Q

Why does lead not appear to react with dilute acids?

A
  • lead appears not to react with dilute hydrochloric acid and dilute sulfuric acid
  • the initial reaction between lead and dilute acid produces a layer of lead(ll) chloride or lead(ll) sulfate
  • this layer is insoluble in water and forms a coat around the metal
  • the coat prevents the metal from reacting with the acid
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8
Q

What is formed when a carbonate and an acid react?

A
  • salt
  • water
  • carbon dioxide
  • e.g. sodium carbonate + hydrochloric acid → sodium chloride + water + carbon dioxide
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9
Q

What is formed when acids react with bases (metal oxide/metal hydroxide)

A
  • salt
  • water
  • e.g. zinc oxide + sulfuric acid → zinc sulfate + water
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10
Q

What is the role of water in the characteristic properties of acids?

A
  • acids only display their properties when dissolved in water
  • this is due to acids producing hydrogen ions when in water
  • hydrogen ions give acids their acidic properties
  • acids only behave as acids when acids ionise in water to produce hydrogen ions
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11
Q

What are the uses of sulfuric acid?

A
  • to manufacture fertilizers such as ammonium sulfate
  • to manufacture detergents
  • for use as battery acid in cars
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12
Q

What is the use of hydrochloric acid?

A
  • used to clean impurities such as rust or scale from metal and aluminium alloys
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13
Q

What is the use of ethanoic acid?

A
  • used in vinegar to act as food preservative and flavor enhancers
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14
Q

What is the use of phosphoric acid?

A
  • added to food and drinks to give them a sour taste
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15
Q

What is a base?

A
  • a base is any metal oxide or hydroxide that reacts with an acid to form salt and water only
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16
Q

What are some common bases?

A
  • sodium oxide (Na₂O)
  • copper(ll) oxide (CuO)
  • aluminium hydroxide (Al(OH)3)
  • magnesium hydroxide (Mg(OH)2)
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17
Q

What is an alkali?

A
  • an alkali is a base that is soluble in water that dissolves in it to form hydroxide ions
  • e.g. sodium oxide
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18
Q

What are some common alkalis?

A
  • sodium hydroxide
  • potassium hydroxide
  • calcium hydroxide
  • barium hydroxide
  • ammonium hydroxide
  • remember i went to the SPA during Circuit Breaker to drink hydroxide
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19
Q

What are the properties of alkalis?

A
  • alkalis feel soapy and have a bitter taste
  • alkalis turn red litmus paper blue
  • alkalis react with acids to form salt and water only (neutralisation reaction)
20
Q

Why is water formed in a neutralization reaction?

A
  • hydrogen ions, from the acid and hydroxide ions, from the alkali react to form water
21
Q

How to tell if a reaction is a neutralization reaction

A
  • is only salt and water are produced, it is a neutralization reaction
  • if anything else e.g. chlorine, ammonia etc is produced, it is not a neutralization reaction
22
Q

What is formed when alkalis are heated with ammonia gas?

A
  • salt
  • ammonia gas
  • water
  • e.g. sodium hydroxide + ammonium chloride → sodium chloride + ammonia gas + water
23
Q

What happens when alkalis react with a solution of one metal salt?

A
  • alkali (containing metal A) + salt (of metal B) → metal hydroxide (of metal B) + salt (of metal A)
  • e.g. 2NaOH (aq) + CuSO4 (aq) → Cu(OH)2 (s) + Na2SO4 (aq)
  • the metal hydroxide appears as a precipitate if insoluble in water
24
Q

What is the use of magnesium oxide?

A
  • used as antacid for relieving gastric pain and making refractory bricks
25
Q

What is the use of sodium hydroxide and potassium hydroxide?

A
  • used in soap preparation
26
Q

What is the use of calcium hydroxide?

A
  • used to reduce acidity of soil
27
Q

What is the use of aqueous ammonia?

A
  • used to make fertiliser
28
Q

What does the term strength refer to?

A
  • the term strength refers to how easily an acid or alkali ionizes when dissolved in water
  • the strength of an acid can be explained in terms of their extent of ionization
29
Q

What is a strong acid?

A
  • a strong acid is a substance that completely ionizes in water/aqueous solution to form/produce hydrogen ions
30
Q

What is an example of a strong acid?

A
  • hydrochloric acid (HCl) is a strong acid
  • all the HCl molecules will ionise in an aqueous solution
31
Q

What is a weak acid?

A
  • a weak acid is a substance that only partially ionises in water/aqueous solution to form/produce hydrogen ions
32
Q

What is an example of a weak acid?

A
  • ethanoic acid (CH3COOH) is an example of a weak acid
  • only some CH3COOH molecules will ionise in an aqueous solution
33
Q

What is the difference between the concentration of an acid and the strength of an acid?

A
  • ‘strong’ and ‘weak’ refer to the extent of ionization of an acid
  • ‘concentrated’ and ‘dilute’ tell us how much of an acid is dissolved in the solution
34
Q

How does one test for a weak and strong acid?

A
  • add drops of universal indicator into each acid
  • if the indicator changes from green to orange/yellow, the acid is weak
  • if the indicator changes from green to red, the acid is strong
35
Q

How the does pH scale work?

A
  • acids have pH values of less than 7
  • alkalis have pH values of greater than 7
  • neutral solutions have a pH value of 7
  • only aqueous solutions have pH values
  • solids and dry gases do not have pH values
36
Q

How does pH relate to the concentration of hydrogen and hydroxide ions?

A
  • an acid with a lower pH has a higher concentration of hydrogen ions
  • an alkaline with a higher pH has a higher concentration of hydroxide ions
37
Q

How can we measure the pH of a solution?

A
  • a chemical compound called a universal indicator
  • pH meter
38
Q

Why is pH of soil important?

A
  • the pH of the soil affects the growth and development of plants
  • most plants do not grow well with a pH of below 5 or above 9
  • most plants grow best when the soil is slightly acidic or neutral
39
Q

What are the different types of oxides?

A
  • acidic
  • basic
  • amphoteric
  • neutral
40
Q

What oxides are acidic?

A
  • carbon dioxide
  • sulfur trioxide
  • phosphorus(V) oxide
41
Q

What is the name of each acidic oxide’s acid produced in water?

A
  • carbon dioxide → carbonic acid
  • sulfur trioxide → sulfuric acid
  • phosphorus(V) oxide → phosphoric acid
42
Q

What are basic oxides?

A
  • metallic oxides
  • solids at room temperature
  • react with acid to form salt and water only
  • can be soluble or insoluble in water
43
Q

What are some examples of amphoteric oxides?

A
  • lead(ll) oxide
  • aluminium oxide
  • zinc oxide
  • remember LAZ
44
Q

What oxides are neutral?

A
  • nitric oxide/nitrogen monoxide
  • carbon monoxide
  • water
  • remember Not Cold Water
45
Q

What must be done for aqueous solutions in ionic equations?

A
  • split the formula into separate positive and negative ions
  • cancel spectator ions (ions that appear exactly the same on the left and right of the arrow)