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GCSE CHEMISTRY > C12.1 - C12.6 - Chemical Analysis✔️ > Flashcards

C12.1 - C12.6 - Chemical Analysis✔️ Flashcards

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1
Q

What is a pure substance?

A

A substance that is made up of just one substance - that substance can either be an element or compound

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2
Q

What are an elements fixed points?

A

The melting and boiling points of an element or a compound are called its fixed point

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3
Q

How can fixed points be used to identify pure elements and compounds?

A

Pure elements and compounds melt and boil at specific temperatures and these fixed points can be used to identify them - meltinga point and boiling point data can be used to distinquish pure substances

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4
Q

What are fomulations?

A

formulations are useful mixtures made up in definite proportions,designed to give a product the best properties possible to carry out its function

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5
Q

Why is chromatography used?

A

Used to seperate mixtures and give information to help identify substances - involves a stationary phase and a mobile phase - seperation depends on the distribution of susbstances between the phases

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6
Q

What are Rբ values?

A

Retention factor value which can be measured and matched against databases to identify substances

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7
Q

Equation for Rբ?

A

Rբ = distance moved by a substance / distance moved by solvent

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8
Q

What will happen to the compounds in a mixture when they seperate?

A

Compounds will seperate into different spots depending on the solvent - but pure compounds will produce a single spot in all solvents

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9
Q

What is the test for hydrogen?

A

Use a burning splint held at the open end of a test tube of the gas - hydrogen burns rapidly with a pop sound

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10
Q

What is the test for oxygen?

A

Uses a glowing splint inserted into a test tube of the gas - splint relights in oxygen

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11
Q

What is the test for chemical dioxide?

A

Uses an aqueous solution or calcium hydroxide (lime water) when carbon dioxide is shaken with or bubbled through limewater the limewater turns milky (cloudy)

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12
Q

What is the test for chlorine?

A

Uses litmus paper - which when damp blue litmus paper is put into chlorine the litmus paper is bleached and turns white

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13
Q

Colour for the lithium ion(Li+) in a flame test?

A

Crimson

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14
Q

Colour for sodium ion (Na+) in a flame test?

A

Yellow

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15
Q

Colour for potassium ion (K+) in a flame test?

A

Lilac

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16
Q

Colour for clacium ion (Ca2+) in a flame test?

A

Orange- red

17
Q

Colour for copper ion (Cu2+) in a flame test?

A

Green

18
Q

Explain how a flame test is set up?

A
  • nichrom wire loop dipped in concentrated hydrochloric aicd and heated (to clean it)
  • dipped in acid again before being dipped into metal compound being tested
  • hold loap in roaring flame of bunsern burner
  • use colour of flame to identify metal ion in the compound
19
Q

Why is sodium hydroxide solution used?

A

Can be used to identify metal ions that form insoluble hydroxides in precipitation reactions

20
Q

What ions form white precipitates when tested with sodium hydroxide solution?

A
  • aluminium ions
  • calcium ions
  • magensium ions
21
Q

What happens if you add more sodium hydroxide to aluminium ions,calcium ions and magensium ions?

A

The precipitate formed with aluminium ions dissolves however the white precipitate formed with calcium or magnesium ions will not dissolve (so calcium and magnesium can be distinguished by a flame test)

22
Q

What colour precipitates forms with copper(II) ions?

A

Blue precipitate

23
Q

What colour precipitates forms with iron(II) ions?

A

Green precipitate is produced

24
Q

What colour precipitates forms with iron(III) ions?

A

Brown precipitate is formed

25
Q

How can you test a substance for being a carbonate?

A

Add dilute acid to a carbonate - it fizzes and produces carbon dioxide gas - the gas turns limewater milky (cloudy)

26
Q

What happens with carbon dioxide gas in limewater - explain why this happens?

A

Carbon dioxide reacts with the alkaline, calcium hydroxide - it forms a white precipitate of calcium carbonate which turns the limewater milky (cloudy)

27
Q

How can you identify halides?

A

By adding dilute nitric acid and then silver nitrate solution which produces a precipitate of silver halide

28
Q

Which colour will the precipitates be when identifying halides?

A
  • Chloride - white
  • bromide - cream
  • iodide - yellow
29
Q

How can you test for sulfates?

A

By adding hydrochloric acid (to remove carbonate ions that would form)and then barium chloride solution which produces a white precipitate of barium sulfate (which tells you sulfate ions are present)

30
Q

Benefits of modern instrumental methods over older?

A
  • they are highly accurate and sensitive
  • they are quicker
  • they enable small samples ro be analysed
31
Q

Disadvantages of using instrumental methods are that the equipment …?

A
  • is usually expensive
  • takes special training to use
  • gives results that can often be interptreted only by comparison with data from known substances
32
Q

What is flame emission spectroscopy?

A

An exmaple of an instrumental method which will tell us which metal ions are present from their characteristics line spectra and also the concentration of metal ions in a solution

33
Q

How are fomulations made?

A

Made by mixing the components in carefully measured quantities to ensure that the product has the required properties - examples formulations are fuels,medicines and foods

34
Q

How can Rբ values be used to identify compounds?

A

Different compounds have different Rբ values in different solvents, which can be used to help identify the compounds

35
Q

How can chromatography be used to seperate mixtures of substances dissolved in a solvent?

A

Mixture of substances dissolved in a solvent move up a piece of chromatography paper - the different substances are seperated because of their different solubilities in the solvent used

GCSE CHEMISTRY (21 decks)

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