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IGCSE CAMBRIDGE CHEMISTRY 2023. > Acids, Bases and Salts. > Flashcards

Acids, Bases and Salts. Flashcards

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1
Q

What happens when acids react with a metal oxides?

A

When acids react with metals they form a salt and hydrogen gas:
Acid + Metal oxides → Salt + Hydrogen.

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2
Q

What happens when acids react with bases?

A

In all acid-base neutralisation reactions, salt and water are produced:

Acid + Base → Salt + Water.

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3
Q

What happens when acids react with metal carbonates?

A

Acids will react with metal carbonates to form the corresponding metal salt, carbon dioxide and water:

Acid + Metal Carbonate → Salt + Carbon Dioxide + Water.

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4
Q

Describe the effect on litmus in acidic conditions.

A

In acidic conditions, blue litmus paper turns red.

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5
Q

Describe the effect of thymolphthalein in acidic conditions.

A

Thymolphthalein turns colorless.

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6
Q

Describe the effect of methyl orange in acidic conditions.

A

Methyl orange indicator turns red.

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7
Q

What are the three important properties of acids?

A

Acids have pH values of below 7, have a sour taste (when edible) and are corrosive.

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8
Q

What are acids?

A

Acids are substances that will lose electrons to form positively charged hydrogen ions (H+ also called protons) when dissolved in water.

Acids are therefore proton donors.

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9
Q

What is an indicator?

A

A substance that changes color when added to acidic or alkaline solutions.

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10
Q

What is a base?

A

Bases are oxides or hydroxides of metals that can neutralize an acid, forming a salt and water.

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11
Q

What is an alkali?

A

An alkali is a soluble base.

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12
Q

Describe the effect on litmus in basic (alkaline) conditions.

A

In basic (alkaline) conditions red litmus paper turns blue.

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13
Q

Describe the effect of thymolphthalein in basic (alkaline) conditions.

A

Thymolphthalein turns blue in alkaline conditions.

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14
Q

Describe the effect of methyl orange in basic (alkaline) conditions.

A

The methyl orange indicator turns yellow.

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15
Q

What four substances can bases be?

A

Bases can be metal oxides, metal hydroxides, ammonia, or carbonates of metals.

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16
Q

What happens when bases react with ammonium compounds?

A

Bases + An Ammonium Compound = Ammonia Gas.

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17
Q

What is a neutralisation reaction?

A

When a base reacts with an acid to form a salt we call the reaction a neutralization reaction.

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18
Q

Describe the neutralization reaction between an acid and an alkali to produce water.

A

H+ (aq) + OH– (aq) → H2O (l)

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19
Q

What do acids and alkalis produce in aqueous solutions?

A

Acids produce H+ ions in aqueous solutions.
Alkalis produce OH- ions in aqueous solutions.

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20
Q

What does the pH scale measure and describe neutrality, acidity, and alkalinity through whole numbers?

A

The pH scale (0 to 14) measures the acidity or alkalinity of a solution, and can be measured using a universal indicator:

  • The lower the pH then the more acidic the solution is.
  • A solution with a pH of 7, such as water, is described as being neutral.
  • The higher the pH then the more basic the solution is.
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21
Q

Soil may become acidic after a number of years. This can be due to:
Give three examples.

A
  • Acid rain.
  • Bacteria and fungi rotting the vegetation so that it releases acids.
  • Use of fertilizers containing ammonium salts.
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22
Q

What is used to neutralize excess acidity in soil?

A

Crushed limestone (calcium carbonate) or lime (calcium oxide) are added to neutralise excess acidity in the soil.

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23
Q

Describe the importance of controlling acidity in soil?

A

If the pH of the soil is too acidic or too basic this would mean that crops would be unable to grow well.

24
Q

What are acids in terms of proton transfer?

A

Acids are proton donors as they ionise in solution producing protons, which are H+ ions.

NOTE - These H+ ions make the aqueous solution acidic.

25
Q

What are bases in terms of proton transfer?

A

Bases (alkalis) are proton acceptors as they ionise in solution producing OH- ions which can accept protons.

NOTE - These OH- ions make the aqueous solution alkaline.

26
Q

Describe the meaning of strong acids.

A

Strong acids ionise completely in water, producing solutions of very low pH for an acid.

27
Q

What kind of an acid is hydrochloric acid and what is the symbol equation?

A

Hydrochloric acid is a strong acid.
HCl(aq) → H+ (aq) + Cl– (aq).

28
Q

Describe the meaning of strong bases.

A

Strong bases ionise completely in water producing solutions of very high pH for a base.

29
Q

Describe the meaning of weak acids.

A

Weak acids partially ionise in water and produce pH values which are closer to the middle of the pH scale.

30
Q

What kind of an acid is ethanoic and what is the symbol equation?

A

Ethanoic acid is a weak acid.
CH3COOH(aq) ⇌ H+ (aq) + CH3COO– (aq)

31
Q

Describe the meaning of weak bases.

A

Weak bases partially ionise in water and produce pH values which are closer to the middle of the pH scale.

32
Q

We can tell if an acid is strong or weak by measuring its electrical conductivity, pH and rate of reaction with metals or metal carbonates:

A
  • A strong acid conducts much better than a weak acid of the same concentration.
  • A strong acid has a lower pH than weak acid of the same concentration.
  • A strong acid reacts faster than a weak acid.
33
Q

We can tell is an acid is strong or weak by measuring its electrical conductivity, pH and rate of reaction with metals or metal carbonates.
What are the reasons for these differences?

A

This is because there is a greater concentration of hydrogen ions in the strong acid compared with the weak acid.

34
Q

Compared with strong bases, weak bases have:

A
  • A lower electrical conductivity.
  • A less alkaline (lower) pH.
  • A slower rate of reaction.
35
Q

What is a universal indicator?

A

A universal indicator is a mixture of different indicators which is used to measure the pH.

36
Q

What are oxides?

A

Oxides are compounds of metal or non-metals.

37
Q

What are the four types of oxides?

A
  • Acidic oxides.
  • Neutral oxides.
  • Amphoteric oxides.
  • Basic oxides.
38
Q

When are basic oxides formed?

A

Basic oxides are formed when a metal element combines with oxygen.

39
Q

What happens when a metal reacts with oxygen (basic oxide reaction)?

A

Metal + oxygen → metal oxide salt.

40
Q

What happens when basic oxides are dissolved in water?

A

When dissolved in water they produce a basic solution with a high pH.

41
Q

Give two examples of basic oxides.

A

CuO - Copper oxide.
CaO - Calcium oxide.

EXTRAS:
BaO - Barium oxide.
MgO - Magnesium oxide.
Fe₂O₃ - Iron (III) oxide.

42
Q

When are acidic oxides formed?

A

Acidic oxides are formed when a non-metal element combines with oxygen.

43
Q

What happens when basic oxides react with acid?
What happens when acidic oxides react with bases?

A

Basic oxides + acid → salt + water.
Acidic oxides + base → salt + water.

44
Q

What happens when acidic oxides are dissolved in water?

A

When dissolved in water they produce an acidic solution with a low pH.

45
Q

Give two examples of acidic oxides.

A

SO₂ - Sulfur dioxide.
CO₂ - Carbon dioxide.

EXTRAS:
P₂O5 - Phosphorus pentoxide.
SO₃ - Sulfur trioxide.
NO₂ - Nitrogen dioxide.

46
Q

What are neutral oxides?

A

Neutral oxides do not react with acids or bases.

47
Q

Give three examples of neutral oxides.

A

N₂0 - Nitrous Oxide.
NO - Nitrogen monoxide.
CO - Carbon monoxide.

48
Q

What are amphoteric oxides?

A

Amphoteric oxides are a curious group of oxides that can behave as both acidic and basic, depending on whether the other reactant is an acid or a base.

NOTE - In both cases, a salt and water is formed.

49
Q

Give two examples of amphoteric oxides.

A

ZnO - Zinc oxide.
Al2O3 - Aluminium oxide.

50
Q

What are the four common laboratory acids?

A

Hydrochloric acid - HCl.
Sulfuric acid - H₂SO₄.
Nitric acid - HNO₃.
Phosphoric acid - H₃PO₄

51
Q

What makes an acidic solution acidic?

A

All acids form hydrogen ions (H+) when dissolved in water, it is the hydrogen ions that make a solution acidic.

52
Q

What are three common laboratory bases?

A

Sodium hydroxide - NaOH.
Calcium hydroxide - Ca(OH)₂.
Ammonia - NH₃.

53
Q

What do alkalis form when dissolved in water?

A

Alkalis form hydroxide ions (OH-) when they dissolve in water.

54
Q

What is a salt?

A

A salt is a compound that is formed when the hydrogen atom in an acid is replaced by a metal/an ammonium group (NH₄).

55
Q

What happens when an acid reacts with a metal hydroxide?

A

Metal hydroxide + acids → salt + water.

56
Q

When is a hydrogen ion formed?

A

A hydrogen ion is formed by the removal of the single electron from a hydrogen atom.

IGCSE CAMBRIDGE CHEMISTRY 2023. (10 decks)

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