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A LEVEL; OCR - CHEMISTRY > 6.4 - Analysis > Flashcards

6.4 - Analysis Flashcards

Pages: 510-533

1
Q

What is added to test an unknown compound to test for an alkene?

A

Bromine water

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2
Q

When you’re testing an unknown compound for an alkene, what property is being tested for?

A

Unsaturation/presence of double bonds

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3
Q

What is occurs if bromine water is added to an unknown soluiost that contains an alkene?

A

The solution will decolourise and become clear

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4
Q

Outline a test to carry out in order to determine if there is an alkene present in an unknown compound:

A
  1. Add 2cm3 of the unknown
  2. Add 2cm3 of orange bromine water to the test tube
  3. Shake
  4. If the solution decolourises and becomes colourless, an alkene is present
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5
Q

What is added to an unknown substance to test if it contains a halogen/is a haloalkene?

A

Aqueous silver nitrate

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6
Q

What are the four different types of haloalkene that can be determined by adding silver nitrate? Does a precipitate form, and if so, what colour?

A
  1. Fluoroalkane - no precipitate
  2. Chloroalkane - white
  3. Bromoalkane - pale cream
  4. Iodoalkane - pale yellow
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7
Q

Outline a test to carry out in order to determine if there is an halogen/haloalkane present in an unknown compound:

A
  1. Add 5 drops of unknown substance to a test tube
  2. Add 1cm3 of aqueous silver nitrate
  3. Place the test tube in a water bath to warm it
  4. Watch for a precipitate.
  5. Fluoroalkane - no precipitate
  6. Chloroalkane - white
  7. Bromoalkane - pale cream
  8. Iodoalkane - pale yellow
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8
Q

When you’re testing an unknown for a phenol, what property is being tested for?

A

The weak, acidic nature of phenols

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9
Q

What are the two different tests done to an unknown substance to test for a phenol?

A
  1. Sodium hydroxide
  2. A carbonate (e.g. sodium carbonate)
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10
Q

Outline the sodium hydroxide test to carry out in order to determine if there is an halogen/haloalkane present in an unknown compound:

A
  1. Add 2cm3 of unknown substance to a test tube
  2. Add 2cm3 of sodium hydroxide solution
  3. If unknown contains an acid, such as a phenol, the solution will fizz, and a colourless solution salt will form
  4. (If not acidic, there will be no reaction)
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11
Q

Outline the carbonate test to carry out in order to determine if there is a halogen/haloalkane present in an unknown compound:

A
  1. Choose a carbonate (e.g. sodium carbonate)
  2. Add 2cm3 of unknown solution to a test tube
  3. Add 2cm3 of sodium carbonate solution
    4.
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12
Q

What are the positive results to the two different tests done to an unknown substance to test for a phenol?

A
  1. Sodium hydroxide test: fizzing and colourless solution of sodium salt will form
  2. Carbonate test: fizzing and carbon dioxide gas is released
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13
Q

What is formed as carboxylic acids react with carbonates?

A
  1. Salt
  2. Carboxylic acid
  3. Water
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14
Q

What is the general equation for the reaction of carboxylic acid reacting with a carbonate (sodium carbonate)?

A

2RCOOH(aq) + Na(2)CO(3)
(s) → 2RCOO
(-)NA+(+) (aq)+ CO(2) (g)+ H(2)O
(l)

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15
Q

Outline the carbonate test to carry out in order to determine if there is a carboxylic present in an unknown compound:

A
  1. Choose a carbonate (e.g. sodium carbonate)
  2. Add 2cm3 of unknown solution to a test tube
  3. Add 2cm3 of sodium carbonate solution
  4. Bubble gas produced in limewater
  5. If limewater goes cloudy, a carboxylic acid is present
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16
Q

What reagent is needed to test if aldehydes/ketones are present in an unknown solution?

A

2,4-dinitrophenylhydrazine (2,4-DNPH)

17
Q

Outline the test to carry out in order to determine if aldehydes/ketones are present in an unknown compound:

A
  1. Dissolve 0.2g of 2,4-DNPH in 1cm3 of sulphuric acid, 2cm3 of water and 5cm3 of methanol
  2. Add 2cm3 of this to 5 drops of the unknown solution
  3. If an aldehyde/kentone is present, a bright orange precipitate will form
18
Q

Outline the test to carry out in order to determine if it is an aldehyde or ketone that is present in an unknown compound:

A
  1. Add 2cm3 of 0.10 mol dm -3 of silver nitrate into a test tube
  2. Add 5 drops of 0.80 mol dm-3
  3. A brown precipitate should form
  4. Add dilute ammonia solution until the brown precipitate dissolves completely
  5. This is Tollen’s reagent
  6. Add 10 drops of the unknown soltuion and place in a warm water bath
  7. If a silver mirror forms, an aldehyde is present
19
Q

What is the other name for the test that determines if it is an aldehyde or ketone that is present in an unknown compound?

A

The silver mirror test

20
Q

What reagent is needed to determine if an unknown solution is a primary or secondary alcohol?

A

Acidified potassium dichromate (VI)

21
Q

Outline the test to carry out in order to determine if an unknown solution is a primary or secondary alcohol?

A
  1. Add 10 drops of the unknown substance to 2cm3 of acidified potassium dichromate (VI)
  2. warm mixture gently in water bath and wait for colour change
  3. If primary alcohol is present, the solution will turn green.

A LEVEL; OCR - CHEMISTRY (6 decks)

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