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Chemistry - IGCSE > Ch 22 - (Chemical analysis) > Flashcards

Ch 22 - (Chemical analysis) Flashcards

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1
Q

What are anions?

A

Negatively charged non - metal ions are known as anions

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2
Q

What are the major tests for anions?

A
  1. Carbonate ions (CO32-)
  2. Halide ions (Cl-, Br-, I-)
  3. Sulfate ions (SO42-)
  4. Sulfite ions (SO32-)
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3
Q

What is the ion for carbonate?

A

CO32-

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4
Q

What is the test for carbonate ion?

A
  • add dilute acid
  • bubble the gas through limewater
  • limewater turns cloudy if carbonate ion is present
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5
Q

What should the observation be for a positive test for carbonate ion?

A
  • fizzing \ effervescence
  • CO2 is produced
  • White precipitate of calcium carbonate
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6
Q

What is the chemical equation for the test of carbonate ions?

A

CO32- (aq) + 2H+ (aq) —> CO2 (g) + H2O (l)

CO2 (g) + Ca(OH)2 (aq) –> CaCO3 (s) + H2O (l)

White precipitate limewater turns cloudy

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7
Q

What are halide ions?

A
  • negative ions
  • anions formed by elements in Group 7
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8
Q

What is the test for halide ions?

A
  • acidify the sample with nitric acid
  • add silver nitrate solution, AgNO3
  • silver halide precipitate
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9
Q

What is the word and symbol equation for the reaction between potassium chloride and silver nitrate?

A

Word:
Potassium chloride + silver nitrate –> potassium nitrate + silver chloride

Symbol:
KCl (aq) + AgNO3 –> KNO3 (aq) + AgCl (s)

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10
Q

What is the observation for the reaction between potassium chloride and silver nitrate?

A

chloride ions form white precipitate

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11
Q

What is the word and symbol equation for the reaction between potassium bromide and silver nitrate?

A

Word:
Potassium bromide + silver nitrate –> potassium nitrate + silver bromide

Symbol:
KBr (ag) + AgNO3 (aq) –> KNO3 (aq) + AgI (s)

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12
Q

What is the observation for the reaction between potassium bromide and silver nitrate?

A

bromide ion forms a cream precipitate of silver bromide

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13
Q

What is the word and symbol equation for the reaction between potassium iodide and silver nitrate?

A

Word:
Potassium iodide + silver nitrate –> potassium nitrate + Silver iodide

Symbol:

KI (aq) + AgNo3 (aq) –> KNO3 (aq) + AgI (s)

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14
Q

What is the observation for the reaction between potassium iodide and silver nitrate?

A

Iodide ions form a yellow precipitate of silver iodide

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15
Q

What is the ion for sulfate?

A

SO42-

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16
Q

What is the test for sulfate ion?

A
  • acidify the sample with dilute hydrochloric acid
  • add a few drops of barium chloride solution
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17
Q

What is the symbol equation for reaction of barium reacting with sulfate?

A

Ba 2+ (aq) + SO42- (aq) –> BaSO4 (s)

18
Q

What is the ion for sulfite?

A

SO3 2-

19
Q

What is the test for sulfite ion?

A
  • add dilute acid
  • warm the mixture gently
  • bubble the gas released through potassium manganate (VII) solution
  • potassium manganate (VII) solution changes from purple to colorless if sulfate ion is present.
20
Q

What is an ammonium ion?

A

NH 4+

21
Q

What is the test for ammonium ions?

A
  • gently warming a solution with the ions and sodium hydroxide solution
  • source of hydroxide solution OH-
  • releases ammonia gas which turns damp red litmus paper
  • cations in aqueous solution can be identified by colour of precipitate they form
  • Transition metals produce hydroxides with distinctive colours
22
Q

What happens if ammonia solution and metal hydroxide are added togteher?

A

It form a metal hydroxide precipitate

23
Q

What happens if excess ammonia solution is added to metal hydroxides?

A
  • some precipitate may re-dissolve
  • that’s why few drops are very slowly dropped
24
Q

How do u test metal ion with ammonia?

A
  • add a few drops of ammonia solution
  • record any color changes or precipitates formed
  • add excess ammonia solution
  • record any color changes to precipitates
25
Q

What happens if precipitate is formed from sodium hydroxide or ammonia solution?

A

Hydroxide is insoluble in water

26
Q

What are 3 metal ions that for white precipitate?

A
  • Aluminium ions (Al3+)
  • Calcium ions (Ca2+)
  • Zinc ions (Zn2+)
27
Q

What happens when calcium ions are tested with NaOH or ammonia?

A
  • White precipitate of calcium hydroxide does not dissolve in excess sodium hydroxide solution
  • precipitate of zinc hydroxide and aluminum hydroxide dissolve in excess sodium hydroxide solution
28
Q

What happens when zinc ions are tested with NaOH or ammonia?

A
  • White precipitate of zinc hydroxide dissolves in excess ammonia solution
  • White precipitate or aluminum hydroxide does not dissolve in excess ammonia solution
29
Q

What is the flame test used for?

A
  • identify metal cations by color of flame
  • ions with diff metals hv diff color
30
Q

How do you do flame test for metal ions?

A
  • dip loop of unreactive metal wore such as nichrome or platinum in concentrated acid
  • hold in blue flame, with no color change
  • test will work only with one type of ion
  • cleans the wire loop and avoid contamination
31
Q

How is the flame test carried out?

A
  • small sample is produced in unreactive metal wire loop such as nichrome or platinum
  • dip loop in solid sample, place in blue flame
32
Q

What was the flame color for metal ion test?

A
  1. Lithium (Li+) - Crimson
  2. Sodium (Na+) - Yellow
  3. Potassium (K+) - Lilac
  4. Calcium (Ca2+) - Red
  5. Barium (Ba2+) - Apple green
  6. Copper (Cu2+) - Blue green
33
Q

What gasses are identified in the test?

A
  1. Ammonia
  2. Carbon dioxide
  3. Chlorine
  4. Hydrogen
  5. Oxygen
  6. Sulfur dioxide
34
Q

What is ammonia?

A

Gas with characteristics sharp chocking smell that turn damp red litmus paper blue

35
Q

How do u test for ammonia?

A
  • hold litmus paper near mouth of test tube
  • avoid touching sides of test tube to prevent traces of sodium hydroxide
36
Q

How do u test for carbon dioxide?

A
  • bubbling gas through aqueous solution of limewater (calcium hydroxide)
  • if CO2 present, limewater is cloudy
37
Q

How is the test for chlorine gas?

A
  • use of litmus paper
  • if it is present, damp blue litmus paper will turn red and then be bleached White
  • it turns red as acids are produced when chlorine comes in contact with water
  • chlorine has sharp chocking smell
  • Shud be handled in fume cupboard due to toxicity
38
Q

What is the test for hydrogen gas?

A
  • holding a burning splint at open end of a test tube of a gas
  • if hydrogen present, it produ es a squeaky pop
  • put splint only in mouth
39
Q

What is the test for oxygen?

A
  • places a glowing splint inside test tube of gas
  • if age is oxygen it relights
40
Q

What is the test for sulfur dioxide?

A
  • sharp chocking smell
  • sulfur dioxide involves bubbling gas through an acidified solution of potassium manganate (VII)
  • if present, it changes from purple to colorless

Chemistry - IGCSE (24 decks)

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