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chemistry IGCSE > acids, bases and salts > Flashcards

acids, bases and salts Flashcards

1
Q

what makes something acidic?

A
  • Substances that taste sour
  • Non-metals burn to form acids
  • In water, acids give up a hydrogen ion (or a proton) to the water molecule, forming a hydroxonium ion (H3Oˆ+)
  • Amount of acidity is measured in the pH scale
  • Acids are naturally occurring substances that dissolve in water
  • Acids also form when oxides of non-metallic substances (like sulphur dioxide) dissolve in water
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2
Q

properties of acids

A

Contain Hˆ+ ions
Soluble in water
Sour to the taste
corrosive
proton donors

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3
Q

properties of bases

A

Metal oxides, carbonates and hydroxides
Some bases are soluble in water and are called alkalis
Soapy to the touch
corrosive
proton acceptors

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4
Q

litmus color in acid

A

red

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5
Q

litmus color in base

A

blue

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6
Q

phenolphthalein color in acid

A

colourless

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7
Q

phenolphthalein color in base

A

pink

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8
Q

universal indicator paper color in acid

A

strong – red
weak – orange/yellow

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9
Q

universal indicator paper color in base

A

strong – purple
weak – blue

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10
Q

thymolphthalein color in acid

A

colorless

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11
Q

thymolphthalein color in base

A

blue

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12
Q

Hydrochloric acid + metal (above hydrogen in reactivity series) (obs., general reaction and example)

A
  • Causes effervescence and heat
    • Gas formed causes a lighted splint to burn with a squeaky pop showing the evolution of hydrogen
    • General reaction: acid + metal —> salt+ hydrogen
    • Example: magnesium + hydrochloric acid → magnesium chloride + hydrogen
      Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
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13
Q

Hydrochloric acid + metal oxide (base) (obs., general reaction and example)

A
  • Neutralization reaction
    • General reaction: Acid + base —> salt + water
    • Example: copper(II) oxide + hydrochloric acid → copper chloride + water
      CuO(s) + 2HCl(aq) → CuCl2(aq) + H2O(l)
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14
Q

Hydrochloric acid + metal hydroxide (base) (obs., general reaction and example)

A
  • Neutralization reaction
    • General reaction: Acid + base —> salt + water
    • Example: sodium hydroxide + hydrochloric acid → sodium chloride + water 
 NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
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15
Q

Hydrochloric acid + metal carbonate (base) (obs., general reaction and example)

A
  • Causes effervescence
    • Gas formed (C02) turns limewater milky
    • General reaction: Acid + metal carbonate —> salt + carbon dioxide + water
    • Example: sodium carbonate + hydrochloric acid → sodium chloride + carbon dioxide + water 
 Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
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15
Q

Hydrochloric acid + ammonia (base)
(obs., general reaction and example)

A
  • Neutralization reaction
    • General reaction: acid + base —> salt
    • Example: ammonia solution + hydrochloric acid → ammonium chloride 
NH4OH(aq) + HCl(aq) → NH4Cl(aq)
16
Q

Brønsted-Lowry theory:

A
  • Acids are proton donors
  • Bases are proton acceptors
  • Water is amphoteric - it can act as both an acid and a base
  • Strong acids are fully ionized or dissociated in aqueous solution (example: HCl(aq) → Hˆ+ (aq) + Clˆ– (aq))
  • Weak acids are partially ionized or dissociated in aqueous solution (example: CH 3 COOH(aq) ⇌ Hˆ+ (aq) + CH 3 COOˆ– (aq))
17
Q

when metals react with oxygen, what do they form?

A

ionic oxides that are basic in nature

18
Q

when non-metals react with oxygen, what do they form?

A

acidic covalent oxides

19
Q
  • Basic oxides: (+ examples)
A

-oxides that form hydroxide ions in solutions
examples: sodium oxide (Na2O), magnesium oxide (MgO), copper oxide (CuO) and calcium oxide (CaO)

20
Q

Group I and some of Group II basic oxides react with water to produce..

A
  • an alkaline metal hydroxide which turns red litmus indicator blue
    example: sodium oxide + water —> sodium hydroxide
21
Q

Basic oxides react with an acid to produce…

A

salt and water
example: magnesium oxide + sulfuric acid —> magnesium sulfate + water (neutralization reaction)

22
Q

acidic oxides (+ examples)

A

oxides that form protons in solutions
examples: sulfur dioxide (SO2) and carbon dioxide (CO2)

23
Q

how is sulfur dioxide formed and what does it produce

A

formed by the combustion of sulfur and produces an acidic solution that tuns blue litmus indicator red

24
Q

sulfur dioxide reacts with water to form..

A

sulfuric (IV) acid (sulfur dioxide + water → sulfuric (IV) acid)

25
Q

carbon dioxide reacts with rainwater to form…

A

carbonic acid (carbon dioxide + water → carbonic acid)

26
Q

Amphotheric oxides:

A

oxides that show both acidic and basic properties
examples: aluminium oxide (Al2O3) and zinc(II) oxide (ZnO)

27
Q

What is a salt?

A
  • Salts are ionic compounds which exist as crystals in the solid state made of cations and anions
  • The crystals are made of ionic lattices
28
Q

method of salt preparation (7 steps)

A
  1. Warm some acid gently (to speed up the reaction)
  2. Add to the acid an excess of either the metal, metal oxide or metal carbonate. This ensures all the acid has been neutralized. For the reactions involving metals or metal carbonates you may need to leave aside until the evolution of gas has stopped.
  3. Filter the mixture to remove the excess solid
  4. Transfer to an evaporating dish and evaporate some of the water off over a Bunsen burner until crystals start to form.
  5. Leave to cool.
  6. Filter to get the crystals.
  7. Dry the crystals on filter paper.
29
Q

hydrated salt

A

form of salt in which water molecules get inside the crystal structure and chemically bond to the cation (metal ion)

30
Q

anhydrous salt

A

salt crystals without water molecules bonded into the crystal structure

31
Q

copper(II) sulfate crystals

A
  • Copper(II) sulfate crystals exist as both a hydrated and an anhydrous salt.
  • Anhydrous copper(II) sulfate is a white crystal. When water is dropped onto it, the color changes to blue - which is the color of hydrated copper(II) sulfate
32
Q

water of crystallization

A
  • water molecules that are chemically bonded into the crystal structure of ionic compounds
    for example: In hydrated copper(II) sulfate there are 5 water molecules bonded within the crystal structure for every molecule of copper sulfate. This has the formula CuSO4 ·5H2O
33
Q

soluble salts:

A

all ammonium, sodium and potassium salts
all nitrate salts
nearly all chloride, bromide and iodide salts
nearly all sulfates
ammonium, sodium and potassium carbonates salts
ammonium, sodium and potassium hydroxide salts

34
Q

insoluble salts:

A

silver chloride, silver bromide, silver iodide and lead chloride
barium sulfate, calcium sulfate and lead sulfate
most carbonates
most hydroxides

35
Q

precipitate (ppt) meaning

A

an insoluble substance that forms when two soluble salts are mixed, causing the solution to go cloudy

chemistry IGCSE (10 decks)

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