Acids, Bases and Salts

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38 Terms

1
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All acids ____ when dissolved in water

dissociate to produce H+ ions

2
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All alkalis___when dissolved in water

dissociate to produce OH- ions

3
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why is universal indicator not used in titration

gradual colour change, can’t see exact point it neutralises

4
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Methyl orange - colour in acidic solution + alkaline solution

  • acidic = red

  • alkaline = yellow

5
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litmus - colour in acidic solution + alkaline solution

  • acidic = red

  • alkaline = blue

6
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Phenolphthalein - colour in acidic solution + alkaline solution

  • acidic = colourless

  • alkaline = pink

7
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What Ph values are acidic?

6→0

8
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neutral PH

7

9
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what PH values are alkaline

8→14

10
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what is a strong acid?

A strong acid dissociates 100% when added to water

11
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what is a weak acid?

only partially dissociates therefore far fewer H+ ions

12
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definition/ characteristics of an Acid

  • dissociate in water to produce H+ ions

  • PH value below 7

  • An acid is a proton donor

13
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Definition of a base

  • neutralise acids to form salt

  • proton acceptors

14
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Alkali definition

  • soluble bases

  • produce OH- ions in water

  • PH value greater than 7

15
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Acid + base →

salt + water

16
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Acid + metal →

salt + hydrogen

17
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Acid + carbonate →

salt + water + carbon dioxide

18
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Acid + Ammonia →

ammonia salt

19
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What are the 2 methods of making salts when the salt is soluble?

  1. titration (uses 2 solutions)

  2. Adding solid base to acid (aq + s)

20
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how to do a titration to obtain a salt

PART 1

  • pipette 25cm3 of solution 1(named in exam) into a conical flask + indicator

  • fill burette with 2nd solution - note starting vol

  • add 1 to 2, swirling

  • stop when 1 drop changes colour

  • note volume added - repeats, mean

  • do again without indicator adding volume calculated

PART 2

  • heat in evaporating basin to get SOME of the water

  • allow to cool, so crystals form

  • filter to obtain crystals

  • dab between paper towels

21
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how to get salt through solid base + acid

PART 1

  • add solid base to acid

  • stop when solid base no longer reacts (excess)

  • filter to remove excess base

PART 2 (same as titration)

  • heat in evaporating basin to get SOME of the water

  • allow to cool, so crystals form

  • filter to obtain crystals

  • dab between paper towels

22
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how to obtain salt when salt is insoluble?

precipitation (aq + aq → s + aq)

23
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how to do precipitaton

  • mix 2 solutions that contain ions of insoluble salt

  • e.g Metal ion needed (NO3) aq

    • (group 1) non metal ion needed

  • filter to get insoluble salt

  • wash with distilled water

  • dab to dry

24
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group 1 solubility

ALL soluble

25
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nitrates solubility

soluble

26
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chlorides solubility

soluble except AgCl and PbCl2

27
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sulfates solubility

soluble except BaSO4, CaSO4 and PbSO4

28
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carbonates solubility

insoluble, except sodium carbonate, potassium carbonate and ammonium carbonate

29
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hydroxides solubility

insoluble except sodium hydroxide and potassium hydroxide and calcium hydroxide(slightly soluble)

30
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write a balanced symbol equation for the reaction between copper oxide and sulfuric acid

CuO(s) + H2SO4 (aq)→ CuSO4 (aq)+ H2O(l)

31
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copper oxide/sulfuric acid practical

why was a measuring cylinder used to measure acid, not burette/pipette

you do not need a precise measurement of HCl - copper added in excess

32
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copper oxide/sulfuric acid practical

why was the acid warmed?

to increase rate of reaction

33
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copper oxide/sulfuric acid practical

why was acid not allowed to boil?

safety reasons - so it doesn’t get on skin

34
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copper oxide/sulfuric acid practical

why was excess copper oxide used?

to ensure all the HCl is reacted/neutralised so the salt is pure

35
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copper oxide/sulfuric acid practical

why is it important to remove excess copper oxide

to ensure we get pure CuSO4 crystals

36
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copper oxide/sulfuric acid practical

why did you leave the sopper sulfate on the windowsill to crystallise, instead of just heating it to boil off all the water

Hydrated Copper sulfate crystals contain water. heating to dry would give anhydrous copper sulfate (white powder)

37
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how to prepare a sample of pure, dry lead (II) sulfate

  1. Add 75 cm3 of lead nitrate and 75 cm3 potassium sulfate to a beaker. Mix the solutions with a glass rod until a precipitate forms.

  2. Put the filter paper in the funnel and place it over the conical flask.

  3. Pour the mixture from the beaker into the funnel.

  4. Use distilled water to wash any solid left in the beaker into the funnel. Wash the filtrate with distilled water. will remove traces of potassium nitrate.

  5. Transfer the filtrate onto an evaporating dish and leave on windowsill

  6. filter out crystals, dab between paper towels to dry

38
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Universal indicator colour - acid/alkali

acid - red

alkali - purple

(scale)