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GCSE - Chemistry (Old) > Acids, Alkalis and Salts > Flashcards

Acids, Alkalis and Salts Flashcards

1
Q

What colour does bromothymol blue go in acids and alkalis?

A

Acids: Yellow
Alkalis: Light Blue

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2
Q

What colour does methyl orange go in acids and alkalis?

A

Acids: Red
Alkalis: Yellow

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3
Q

What colour is phenolphthalein in acids and alkalis?

A

Acids: Colourless
Alkalis: Purple, Pink

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4
Q

What are ions are acids the sources of?

A

Hydrogen, H+

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5
Q

What ions are alkalis the source of?

A

Hydroxide, OH-

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6
Q

What colour is litmus in acids, neutral and alkalis?

A

Acids: Red
Neutral: Purple
Alkalis: Blue

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7
Q

What is an acid?

A
  • Source of H+ ions
  • pH less than 7
  • Release H+ ions of dissolved in water
  • ‘Dissociate in water to produce hydrogen ions’
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8
Q

What is a base?

A
  • Can neutralise an acid
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9
Q

What is the difference between bases and alkalis?

A

An alkali is a soluble base. It is a source of OH- ions. They have pH above 7.

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10
Q

Acid + Base

A

Acid + Base -> Salt + Water

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11
Q

Give examples of a strong and weak acids.

A

Strong: Sulphuric
Weak: Vinegar, Lemon Juice, Bee Sting

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12
Q

Give examples of neutral substances.

A

Distilled water, salt water

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13
Q

Give examples of weak and strong alkalis.

A

Weak: Baking powder, Ammonia
Strong: Sodium Hydroxide

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14
Q

What colours does universal indicator turn in different pHs?

A 
Strong acid: Red
Weak acid: Yellow
Neutral: Green
Weak alkali: Blue
Strong alkali: Purple
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15
Q

What is the difference between hydrogen chloride and hydrochloric acid?

A

In water, hydrogen gas dissolves to form hydrochloric acid. The solution is acidic because the hydrogen chloride dissociates into H+ and Cl- ions. pH is a measure of H+ ions, so it is acidic. Hydrogen chloride as a gas is not acidic.

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16
Q

What is the state of hydrogen chloride in room temperature?

A

Gas

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17
Q

Acid + Carbonate

A

Acid + Carbonate -> Salt + Water + Carbon Dioxide

18
Q

Acid + Metal

A

Acid + Metal -> Salt + Hydrogen

19
Q

How do H+ ions and OH- ions react?

A

H+ + OH- -> H2O

20
Q

What happens to H+ ions in water?

A

They attach themselves to water molecules:

H+ + H2O -> H3O+

21
Q

What happens when hydrogen chloride is dissolved in organic solvents, such as methylbenzene?

A

It cannot ionise to form H+ and Cl-, and it stays as HCl.

22
Q

Why is HCl acidic in water but not in methylbenzene?

A

It cannot dissociate into H+ and Cl- ions (the H+ make it acidic) in the methylbenzene like it can in water and so it stays as HCl.

23
Q

What is a salt?

A

A substance that is formed when the hydrogen in an acid is replaced by a metal.

24
Q

What is the formula for hydrochloric acid?

A

HCl

25
Q

What is the formula for sulphuric acid?

A

H2SO4

26
Q

What is the formula for nitric acid?

A

HNO3

27
Q

What is the formula for phosphoric acid?

A

H3PO4

28
Q

What is the formula for ethanoic acid?

A

C2H4O3

29
Q

What is the test for hydrogen?

A

Holding a lighted splint near the gas and listening for a squeaky pop.

30
Q

What are the general rules for soluble salts?

A
  • All nitrates
  • All sodium potassium, sodium and ammonium salts
  • Most chlorides (except AgCl, PbCl2, Hg2Cl2)
  • Group 1 carbonates are soluble (most are insoluble)
  • Most sulphates (except PbSO4, CaSO4, BaSO4)
  • Group 1 hydroxides + Ca(OH)2, Ba(OH)2 (most are insoluble)
31
Q

What are the solubility rules about nitrates?

A

All are soluble

32
Q

What are the solubility rules about sodium, potassium and ammonium salts?

A

All are soluble

33
Q

What are the solubility rules about chlorides?

A

Most are soluble except:

AgCl, PbCl2, Hg2Cl2

34
Q

What are the solubility rules about carbonates?

A

All group 1 are soluble.

Most are insoluble.

35
Q

What are the solubility rules about sulphates?

A

Most are soluble except:

PbSO4, CaSO4, BaSO4

36
Q

What are the solubility rules about hydroxides?

A

Group 1, Ca(OH)2 and Ba(OH)2 are soluble.

Most are insoluble.

37
Q

Describe the process of formation of an insoluble salt.

A

• Mix two solutions - one with the correct positive and one with the negative ion
• Remember each of the first solutions must contain a soluble compound, or it can’t be a solution
• The reaction should form a solution and precipitate
• Filter this to get the precipitate - this is the salt
NO ACID REQUIRED

38
Q

What is the process of making an insoluble salt called?

A

A precipitation reaction

39
Q

Why can’t sodium, potassium or ammonium salts be made using the ‘adding an excess of solid and then filtering it off’ method?

A

That method requires an insoluble base, and potassium, sodium and ammonium salts and compounds are always soluble.

40
Q

What method can be used to make a soluble salt which is not a sodium, potassium or ammonium?

A

• Get the correct metal oxide, carbonate or hydroxide, making sure it is insoluble
• Get the correct acid
• Keep adding the insoluble base to the acid until the reaction stops and there is an excess at the bottom of the acid
• Filter off this excess, heat the remaining solution for some time and evaporate it to get crystals
REQUIRES AN ACID

41
Q

How can you test for carbon dioxide?

A

Bubble through limewater, turns cloudy white

42
Q

How can you test for hydrogen?

A

Lighted splint would cause a squeaky pop

GCSE - Chemistry (Old) (14 decks)

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