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CHEM IGCSE > acids, alkalis and titrations > Flashcards

acids, alkalis and titrations Flashcards

1
Q

acids are substances that turn litmus paper what colour

A

red, yellow or orange

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2
Q

acids have a pH

A

below 7

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3
Q

bases turn litmus paper what colour

A

sark green, blue or purple

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4
Q

what are bases called if they dissolve in water

A

alkali’s

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5
Q

bases react with _____ in acids

A

H+ ions

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6
Q

use of universal indicator

A

measure pH of a solution

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7
Q

colour of universal indicator with acid

A

red

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8
Q

colour of universal indicator with alkali

A

blue

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9
Q

use of phenolphalein indicator

A

determine the end point of a strong or weak acid

TITRATIONS

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10
Q

what is an alkali

A

a soluble base

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11
Q

colour of phenolphthalein indicator in acid

A

colourless

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12
Q

colour of phenolphthalein indicator in alkali

A

pink

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13
Q

colour of methyl orange in acid

A

red

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14
Q

colour of methyl orange in alkali

A

yellow

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15
Q

how is universal indicator used

A

a drop of it is added to the solution and colour is matched to the colour chart which indicates the pH

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16
Q

use of methyl orange indicator

A

determine the end point of a strong acid- strong alkali or strong acid- weak alkali

TITRATIONS

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17
Q

When acids are added to water they form

A

positive hydrogen ions

18
Q

what makes a solution acidic

A

presence of hydrogen ions

19
Q

when alkalis are added to water, what is formed

A

negative hydroxide ions

20
Q

what makes a solution alkaline

A

hydroxide ions

21
Q

what happens when an acid and an alkali react

A

a neutralisation reaction

22
Q

Ionic equation of neutralisation ( H)

A

H⁺ + OH⁻ —-> H₂O

23
Q

4 common indicators

A

litmus
universal
phenolphthalein
methyl orange

24
Q

the point at which an indicator changes colour is known as the

A

end point

25
Q

neutralisation is

A

a reaction between a base/alkali and an acid which forms a salt and water

26
Q

what is a base

A

a proton acceptor ( they are metal oxides, hydroxides or carbonates)

27
Q

strong acids in do what water

A

completely ionize

28
Q

properties of strong acids (3)

A

produce high concentrations of H+ ions in solution

  • have a low pH 0-3
  • react more vigorously with metals, carbonates and bases
29
Q

weak acids do what in water

A

partially ionize

30
Q

if weak acids only partially ionize in water, what does that mean about the H+ions

A

only some of their molecules release H+ions

31
Q

properties of weak acids (3)

A
  • produce lower concentration of H+ions in solution
  • have a pH of 4-6
  • react less vigorously compared to strong acids
32
Q

carboxylic acids are what type of acids

A

weak acids

33
Q

carboxylic acids contain a functional group of what atoms (3)

and how are they arranged

A

carbon , hydrogen and oxygen atoms

COOH

34
Q

Examples of carboxylic acids

A

methanoic ( HCOOH)

ethanoic ( HC₃ COOH)

35
Q

How do bases neutralise acids

A

by combining with the hydrogen ions in them

36
Q

word reaction of a base neutralising an acid

A

acid + base —> salt + water

37
Q

acids in aqueous solution are a source of what ions

A

positive hydrogen ions

38
Q

alkalis in aqueous solution are a source of what ions

A

negative hydroxide ions

39
Q

titrations are a method of

A

analysing the concentration of solutions

40
Q

acid-base titrations determine

A

exactly how much alkali is needed to neutralise a quantity of acid – and vice versa

41
Q

Titrations can also be used to prepare

A

salts

42
Q

PRACTICAL- HOW TO CARRY OUT AN ACID- BASE TITRATION

A
  • Place exactly 25cm³ sodium hydroxide in conical flask
  • Place the conical flask on a white tile so the tip of the burette is inside the flask
  • Add a few drops of a suitable indicator to the solution in the conical flask

Perform a rough titration by taking the burette reading and running in the solution in 1 – 3 cm3 portions, while swirling the flask vigorously

Quickly close the tap when the end-point is reached (sharp colour change) and record the volume, placing your eye level with the meniscus

Now repeat the titration with a fresh batch of sodium hydroxide

As the rough end-point volume is approached, add the solution from the burette one drop at a time until the indicator just changes colour

Record the volume to the nearest 0.05 cm3

Repeat until you achieve two concordant results (two results that are within 0.1 cm3 of each other) to increase accuracy

CHEM IGCSE (31 decks)

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