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Chemistry Igcse > C8 > Flashcards

C8 Flashcards

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1
Q

What is relative acidity and alkalinity in terms of H+ and OH-?

A

Water -> neutral
When a substance is dissolved in water it becomes:
Acidic
More H+
Alkaline
More OH-
Neutral
Equal number of both

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2
Q

What is the pH scale?

A

A numerical scale which is used to show the acidity or alkalinity of a solution (1-14 and extra acidic can have values from 0-1)

Acidic -> less than 7 (lower)
Alkalis -> more than 7 (higher)
Neutral -> 7

pH measures concentration of H+ (inverse relationship)

Logarithmic -> change of 1 on scale is change in concentration by 10

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3
Q

What are indicators?

A

Shows if a solution is acidic or alkaline or neutral by a color change

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4
Q

What are the different types of indicators?

A

Two color indicators:
Distinguish acids and alkalis
Litmus paper (from lichen)

Synthetic indicators:
Organic compounds that are sensitive to changes in acidity

methyl orange-> used in acid-alkali titrations -> show endpoint ( point when color of solution changes completely with the addition of an indicator)

Universal indicator:
Mixture of different indicators which is used to measure pH
A drop is added to solution and the color is matched with color chart (look on docs for diagram)
Generally:
Warmer colors - acid
Greens - neutral or close
Cooler colors - alkali

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5
Q

What are some characteristic of acids?
pH value
___ when edible
___
Can neutralize __
Acid added to water->
Presence of ____
Proton ____

A

pH less than 7
Sour when edible
Corrosive
Can neutralise a base (forms a salt+water)
Acids added to water-> positively charged hydrogen ions
Presence of H+ makes it an acid
Proton donors (H+)

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6
Q

How can acids be arranged?

A

By amount of H+ per molecule
Monoprotic acid-> 1 H+ ion (hydrochloric acid, nitric acid)
Etc…

How ‘well’ they split into ions when put into water
Strong acid- completely dissociates into ions (hydrochloric, nitric)
Weak acid- partially dissociates into ions (ethanoic, carbonic)

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7
Q

How does the amount of H+ and strength of an acid relate to concentration?
(Dilute solution of HCl and concentrated solution of ethanoic acid)

A

Example:
A dilute solution of HCl (monoprotic) will be stronger than a concentrated solution of Ethanoic acid (monoprotic)
-> Most of HCl dissociate while very few of the ethanoic acid dissociate (but ethanoic is more acidic)

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8
Q

How are salts produced by acids?

A

When the H+ molecules in the acid are replaced by other positive ions (metal or ammonium ions) this creates salts

Hydrochloric acid → CHLORIDES
Sulphuric acid → SULPHATES/HYDROGEN SULPHATES
Nitric acid → NITRATES

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9
Q

What is created when metal reacts with acids?

A

Note: only metals above hydrogen in reactivity series will react to dilute acids

Acid + metal -> salt + hydrogen
Name of the salt related to acid (anion in acid) and metal

Ex:
Hydrochloric acid + magnesium -> magnesium chloride and hydrogen
Mg + 2 HCl -> MgCl2 + H2
Metal anion-ide and hydrogen

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10
Q

What is created when an acid is mixed with a base?

A

Water

Metal oxide + metal hydroxides (alkali) -> bases
React with acid -> neutralisation reaction
Acid + base -> salt + water (hydroxides or oxides)

Ex:
Hydrochloric acid -> magnesium chloride and water
Mg(OH)2 + 2HCl -> MgCl2 + 2 H2O

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11
Q

What is created when acid reacts with metal carbonates?

A

Forms corresponding metal salt, carbon dioxide and water
Acidic + metal carbonate -> salt + carbon dioxide + water

Ex:
Hydrochloric acid + magnesium carbonate -> carbon dioxide and water
MgCO3 + 2 HCl -> MgCl2 + CO2 + H2O

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12
Q

What is a neutralisation reaction?

A

Acid + base -> water
H+ + OH- => water

Ex:
HCl + NAOH -> H2O + NaCl
H+ + OH- => H2O
Na+ + Cl- => NaCl

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13
Q

What are the characteristics of bases?
pH value
What is alkali?
Can be neutralized by…
____ of metals
Alkali added to water->___
Presence of_____

A

pH value higher than 7
Alkali -> water soluble base
Can be neutralized by acid (form salt+water)
Usually oxides or hydroxides of metals
Alkali added to water -> OH-
Presence of OH- => base

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14
Q

What happens when alkalis and ammonium salts react?

A

Ammonium salts -> decomposition when warmed with alkali
Ammonia is weak base but volatile -> easy to displace from salt with another alkali

Alkali + ammonium salt -> salt, water, ammonia

NH4Cl + NaOH -> NaCl + H2O + NH3

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15
Q

What is the use of an alkali ammonium salt reaction?

A

Used to confirm presence of ammonium ions
Solution + alkali warmed
Damp red litmus paper will turn blue if ammonia is present

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16
Q

Why is it important to control acidity in soil?

A

If the soil is too alkaline or acidic, the crops won’t grow properly.
Usually soil is too acidic so a base (limestone, slaked lime, quicklime) can neutralize (usually sprayed in soil)

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17
Q

How can burning fossil fuel and factory waste be affected by acidity?

A

Air:
Burning fossil fuels release gases (nitrogen oxides and sulphuric dioxides) and react with the water and air -> acid rain
Build erode, harmful for soil, plants, water sources

Water:
Factory waste -> acidic and can leak into water
Usually treated with slaked lime

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18
Q

Define acids and bases in terms of proton (H+) transfer (aqueous solutions)

A

Acid are protons donors -> they ionise in solutions by producing protons (H+)

Bases are protons acceptors -> accept protons donated by acids

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19
Q

Why do alkali solutions and acidic solutions conduct electricity better?

A

They both have more H+ or OH- ions, allowing them to conduct electricity better

This can also be used to prove that the solution has ions

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20
Q

Why is water important to certain acids?

A

hydrogen chloride gas are dissolved in water and acidic solution is created
(Covalent molecules -> pure
Becomes acid when dissolved in water)

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21
Q

Define oxide

A

A compound made from one or more atoms of oxygen combined with one other element (MgO, ZnO, CO2 etc)

22
Q

Define acidic oxide

A

A nonmetals element combines with oxygen
When dissolved in water forms an acidic solution

23
Q

Define basic oxide

A

Metal element combines with oxygen
When dissolved in water produces basic solution (alkali)

24
Q

Define neutral oxides

A

Oxides that do not react with either acids or bases and are ‘neutral’ (N2O, NO, CO, H2O etc)

25
Q

Define amphoteric oxides

A

Can behave as both acidic and basic depending on wether the other reactant is an acid or base
Can neutralise both acids and bases
(ZnO, Zn(OH)2, Al2O2, Al(OH)3)
Zinc/ aluminum oxide/hydroxide

26
Q

How can the salt of aluminum and zinc be distinguished from others?

A

By adding sodium hydroxide to either salt a white precipitate of the metal hydroxide will form

27
Q

What types of oxides apply to nonmetal and metal oxides?

A

Nonmetal
Acidic
Neutral

Metal
Basic
Amphoteric (can react as a base and acid)

28
Q

How are salts named?

A

First part
Metal, metal oxide or metal carbonate used in reaction

Second part
From acid

Ex: sodium hydroxide + hydrochloric acid -> sodium chloride

29
Q

How can salt be prepared by adding acid to a metal, insoluble carbonate or base (method A)?

A

Metal
1. Zinc powder + sulphuric acid
2. Filter excess zinc out
3. Evaporate water from solution -> zinc sulphate

Insoluble base
1. Copper oxide + sulphuric acid
2. Filter out excess
3. Evaporate water -> copper sulfate

Insoluble carbonate
1. Calcium carbonate + nitric acid
2. Filter out excess
3. Evaporate water -> calcium nitrate

30
Q

How can salt be prepared by reacting a dilute acid and alkali (method B)?

A

Neutralizing alkali with acid via titration
1. add alkali and indicator to flask
2. Add acid to burette (note starting volume)
3. Slowly add acid to alkali until indicator changes color
4. Calculate volume of acid
5. Repeat previous steps without indicator
6. Evaporate water

31
Q

How can salt be prepared by reacting 2 soluble salts to form insoluble precipitate (method C)?

A

Lead (II) nitrate + potassium sulphate
1. Dissolve in water and mix together
2. Filter to remove precipitate from mixture
3. Wash precipitate with distilled water (remove potassium nitrate solution)
4. Leave to dry

32
Q

Salts and their solubility:
Sodium potassium ammonium
Nitrates
Chlorides
Sulfates
Carbonates
Hydroxides

A

Sodium potassium ammonium:
All soluble
Nitrates:
All soluble
Chlorides:
Most are soluble (-sliver + lead (II))
Sulfates:
Most are soluble (-barium, calcium, lead (II))
Carbonates:
Most are insoluble (-sodium, potassium, ammonium)
Hydroxides:
Most are insoluble (-sodium, potassium, ammonium, calcium (partially))

33
Q

What test can be performed to identify ammonium (aqueous cation)?

A

Add dilute sodium hydroxide to ammonium (aqueous cation) and heat

Gas with a strong smell
Red litmus paper -> blue

34
Q

What test can be performed to identify calcium (aqueous cation)?

A

Add dilute sodium hydroxide to calcium until there is excess
White precipitate forms (insoluble)

35
Q

What test can be performed to identify copper (II) (aqueous cation)?

A

Add dilute sodium hydroxide or ammonium solution
Blue precipitate (insoluble)

36
Q

What test can be performed to identify iron (II) (aqueous cation)?

A

Add dilute sodium hydroxide or ammonium solution
Pale green precipitate (insoluble)

37
Q

What test can be performed to identify iron (III) (aqueous cation)?

A

Add dilute sodium hydroxide or ammonium solution
Red brown precipitate (insoluble)

38
Q

What test can be performed to identify zinc (aqueous cation)?

A

Add dilute sodium hydroxide or ammonium solution
White precipitate (soluble)

39
Q

What test can be performed to identify lithium (cation)?

A

Flame test
Crimson flame

40
Q

What test can be performed to identify sodium (cation)?

A

Flame test
Yellow/orange flame

41
Q

What test can be performed to identify potassium (cation)?

A

Flame test
Lilac flame

42
Q

What test can be performed to identify copper (II) (cation)?

A

Flame test
Blue green flame

43
Q

What test can be performed to identify chloride (anion)?

A

Dissolve in water, aqueous silver nitrate under acidic conditions (diluted nitric acid)
White precipitate forms

44
Q

What test can be performed to identify bromide (anion)?

A

Dissolve in water, aqueous silver nitrate under acidic (dilute nitric acid) conditions
Cream precipitate

45
Q

What test can be performed to identify carbonate (anion)?

A

Add dilute acid (hydrochloric) to solid and test gas using limewater
Lime water turn milky

46
Q

What test can be performed to identify nitrate (anion)?

A

Add aqueous sodium hydroxide and then reduction with aluminum
Ammonia gas released (smell+litmus paper test)

47
Q

What test can be performed to identify sulfate (anions)?

A

Acidify with dilute nitric acid and add aqueous barium nitrate
White precipitate

48
Q

What test can be performed to identify ammonia (gas)?

A

Damp red litmus paper -> blue

49
Q

What test can be performed to identify carbon dioxide (gas)?

A

Pass through limewater
Limewater -> milky white

50
Q

What test can be performed to identify hydrogen (gas)?

A

Exposed to lighted splint -> pop

51
Q

What test can be performed to identify chlorine (gas)?

A

Damp blue litmus paper -> white

52
Q

What test can be performed to identify oxygen (gas)?

A

Exposed to a glowing splint -> relights

Chemistry Igcse (10 decks)

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