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chemistry igcse > Salts > Flashcards

Salts Flashcards

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1
Q

Define salt

A

ionic compounds formed in a reaction with an acid

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2
Q

Name 4 examples of salts

A
  • halides
  • nitrates
  • sulfates
  • phosphates
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3
Q

Guess the correct word to fill in the blank:

Salts are generally acids/neutral/bases.

A

neutral

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4
Q

What are the 3 properties of salts?

A
  • high mpt (bc of strong electrostatic forces)
  • conduct electricity as (l) and (aq)
  • soluble in water (with exceptions)
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5
Q

Define ‘dissociating’ in salts

A

breaking the strong electrostatic forces between particles

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6
Q

Why is CaSO₄ insoluble?

A

because the solvent cannot break the strong electrostatic forces between particles (the charge of Ca is 2⁺ and the charge of SO₄ is 2⁻ so the electrostatic forces are too strong)

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7
Q

What are the 7 solubility rules?

A

Most importat (dominant) rules:
1) all compounds of group 1 are soluble
2) all nitrates are soluble
——————————————————————————-
3) all halides are soluble except if they also contain Ag⁺ or Pb²⁺

4) all sulfates are soluble except if they also contain Ca⁺, Sr⁺, Ba²⁺, Pb²⁺

5) All hydroxides are insoluble

6) all carbonates are insolubles

7) all oxides are insoluble (but gp 1 reacts with water)

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8
Q

Define precipitation

A

reaction of 2 solutions to form a solid

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9
Q

Give any example of a precipitation reaction

A

AgNO₃ (aq) + NaBr (aq) → NaNO₃ (aq) + 【AgBr (s) 】➡ precipitate/ppt

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10
Q

What is the difference between a precipitation and a displacement reaction?

A

displacement: a more reactive element replaces another less reactive element.

precipitation: a more soluble element replaces another less soluble element. a solid is formed.

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11
Q

Write a preparation of PbI₂ (you can use other examples)

A

PbI₂ → Pb(NO₃)₂ (soluble substance)
→ KI (insoluble substance)

Pb(NO₃)₂ + KI → PbI₂ + 2KNO₃

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12
Q

How are impurities removed from the residue after a precipitation reaction?

A

Step 1: Wash residue with distilled water to remove soluble impurities

Step 2: evaporate water on hot plate

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13
Q

What are the 5 steps to write an ionic equation?

A

i) write symbol equation

ii) add state symbols

iii) identify ionic compounds that are aqueous

iv) separate those compounds into ions

v) cancel out left/right

(find examples in notebook)

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14
Q

Acid + base →

A

salt + water

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15
Q

Acid + metal carbonate →

A

salt + water + carbon dioxide

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16
Q

Fill in the blanks:

During salt preparation, the salt produced needs to be 1.___________ and therefore the base used needs to be 2.___________.

A
  1. isolated / pure
  2. insoluble
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17
Q

Which of the reactants should be in excess for salt preparation?

A

the base needs to be in excess

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18
Q

How will the excess base for salt preparation be separated?

A
  1. filter
  2. evaporate
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19
Q

What is the general method for salt preparation?

A

1) measure 𝑥 cm³ of H₂SO₄ into a conical flask

2) add excess base and heat on a hot-plate (if carbonate, wait until no more effervescing. if oxide, wait until solid disappears)

3) filter to remove excess base (residue = base, filtrate = salt + water)

4) heat filtrate in an evaporating basin until ¾ of water has evaporated or until crystals begin to form

5) leave to crystallise

6) filter to remove excess water

7) collect residue

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20
Q

Why should some of the water be left when evaporating the filtrate during salt preparation?

A

1) forms large crystals

2) to avoid salt decomposing

3) to form hydrated crystals

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21
Q
A
22
Q

What method needs to be used to prepare group 1 salts?

A

titration

23
Q

What is the general method for preparing group 1 salts?

A

1) measure 𝑥cm³ of base into a conical flask (using a pipette)

2) add 2 drops of indicator (methyl orange or phenophalein)

3) fill burette with acid and record initial volume

4) add acid to base (slowly) until it turns red (methyl orange)

24
Q

What types of particles do ionic compounds consist of?

A

anions and cations

25
Q

What are the 4 tests for cations?

A

1) flame test
2) NaOH test
3) NH₃ test
4) NH₄⁺ test

26
Q

What are the 5 tests for anions?

A

1) halide test
2) SO₄²⁻ test
3) SO₃²⁻ test
4) CO₃²⁻ test
5) NO₃⁻ test

27
Q

When a cation is heated, the particle moves from ground state to…?

A

exited state

28
Q

Explain what happens when an electron is promoted

A

the electron absorbs energy and moves further from the nucleus

29
Q

What happens when the heat previously put on a cation is removed?

A

as the electron returns back to ground state, energy is released as light

30
Q

What does the color of light produced when an electron moves from exited state to ground state depend on?

A

the color of light depends on the wave length of the light emitted

31
Q

Which color in the electromagnetic spectrum has the most energy and which has the least energy?

A

most energy - purple

least energy - red

32
Q

Why do some ions release more energy when going from ground state to exited state?

A

because depending on the charge, the attraction force is stronger. in ²⁺ ions, the attraction force is stronger than those in a ⁺ ion.

33
Q

What is the method for the flame test?

A

1) clean wire / needle with concentrated HCl

2) dip wire in acid (HCl) (to wet needle) and place in compound

3)place compound in blue bunsen flame

34
Q

Complete the table to determine the light each cation emits:
+———–+———————|
| Li ⁺ | |
+———–+———————|
| Cu⁺ | |
+———–+———————|
| Na⁺ | |
+———–+———————|
| Ba⁺ | |
+————+——————–|
| K⁺ | |
+————+——————–|
| Mg²⁺ | |
+————+——————–|
| Ca²⁺ | |
+————+——————–|

Cation | Color |

A

+———–+———————|
| Li ⁺ | bright red |
+———–+———————|
| Cu⁺ | blue/green |
+———–+———————|
| Na⁺ |orange/yellow|
+———–+———————|
| Ba⁺ | apple-green |
+————+——————–|
| K⁺ | lilac |
+————+——————–|
| Mg²⁺ | colorless |
+————+——————–|
| Ca²⁺ | brick-red |
+————+——————–|

Cation | Color |

35
Q

What state is a precipitate?

A

solid

36
Q

What 2 ions can be used for a cation test? Which one is preferable?

A

OH⁻ or CO₃²⁻
OH⁻ is preferable

37
Q

GO MEMORISE THE PRECIPITATION CATIONS TESTS IN NOTEBOOK

A

ok…

38
Q

What cations could be used for the sulfate anion test? Which one would be preferable and why?

A

Ca²⁺/Sr²⁺/Ba²⁺/Pb²⁺
Ba²⁺ is preferable because it is most insoluble

39
Q

What is the method for the sulfate test?

A

1) dissolve sample in water
2) add any acid except H₂SO₄ (to neutralise or remove OH⁻/CO₃²⁻)
3) add Ba(NO₃)₂
4) if sulfate is present, ppt. is formed

40
Q

What is the method for the sulfite test?

A

1) add any acid (HCl)
2) collect gas produced
3) expose gas to KMnO₄ or K₂Cr₂O₇

41
Q

What is the equation for the sulfate test?

A

Ba(NO₃)₂ + NaSO₄ → BaSO₄ + 2NaNO₃

42
Q

What is the equation for the sulfite test?

A

XSO₃ + HCl → XCl₂ + H₂O + SO₂

43
Q

What is the method for the carbonate test?

A

1) add any acid (except carbonic acid)
2) collect gas produced
3) add gas to limewater

44
Q

What is the equation for the carbonate test?

A

XCO₃ + 2HCl → XCl₂ + H₂O + CO₂

45
Q

What is the method for the ammonium test?

A

1) react compound with NaOH
2) heat
3) collect gas and expose to damp red litmus paper → blue

46
Q

What is the equation for the ammonium test?

A

NH₄X + NaOH → NaX + H₂O + NH₃

47
Q

What is the method for the nitrate test?

A

1) add compound to NaOH
2) react with aluminium powder
3) heat
4) collect gas and expose to damp red litmus paper → blue

48
Q

What is the method for the halide test?

A

1) dissolve sample in water
2) add any acid (HNO₃) except for HCl (to remove OH⁻/CO₃²⁻)
3) add AgNO₃ and observe color of ppt.

49
Q

Which test should you do before halide?

A

SULFATE TEST FIRST!!!

50
Q

What are the results for the halide test?

A

chemistry igcse (10 decks)

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