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chemical analysis Flashcards

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1
Q

what is the test for hydrogen?

A

a pop sound when a lighted splint is in a at the end of test tube containing hydrogen gas

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2
Q

what is the test for oxygen?

A

a glowing splint relights in a test tube of oxygen

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3
Q

what is the test for carbon dioxide?

A

lime water ( calcium hydroxide ) turns cloudy when co2 is present

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4
Q

what is the test for chlorine?

A

litmus paper is bleached or turns white

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5
Q

what is the test for water?

A

copper sulphate turns blue

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6
Q

what is a pure substance?

A

a single element or compound not mixed with any other substance

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7
Q

how can boiling/melting points be used to determine the impurity of a substance?

A

the higher the boiling point ( from the pure element/compound) the impurer the substance - vicea versa for melting point

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8
Q

how do you identify positive ions in a solid ionic compound?

A

the flame test: dip wire loop into conc hcl and then into solid compound and then place in Bunsen flame

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9
Q

how do you identify positive ions in a solution of an ionic compound?

A

add naoh

sodium hydroxide

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10
Q

how do you identify halide ions in a solution of an ionic compound?

A

add dilute nitric acid then the silver nitrate

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11
Q

what colour is the flame in a flame test when sodium is present?

A

yellow

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12
Q

what colour is the flame in a flame test when potassium is present?

A

lilac

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13
Q

what colour is the flame in a flame test when calcium is present?

A

orange/red

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14
Q

what colour is the flame in a flame test when barium is present?

A

green

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15
Q

what is the result when chloride is present ( in a test for negative ions )?

A

white precipitate

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16
Q

what is the result when chloride is present ( in a test for negative ions )?

A

white precipitate

17
Q

what is the result when bromide is present ( in a test for negative ions )?

A

cream precipitate

18
Q

what is the result when iodide is present ( in a test for negative ions )?

A

yellow precipitate

19
Q

what is the test for sulphate and what is the positive result?

A

white precipitate

add dilute hcl and then barium chloride

20
Q

how do you differentiate between aluminium, calcium and magnesium?

A

add excess naoh and then only aluminium will form a colourless solution
then use a flame test to differentiate between calcium and magnesium

21
Q

what is the positive result for a test for an ionic solution containing aluminium?

A

white precipitate

22
Q

what is the positive result for a test for an ionic solution containing calcium?

A

white precipitate

23
Q

what is the positive result for a test for an ionic solution containing magnesium?

A

white precipitate

24
Q

what is the positive result for a test for an ionic solution containing copper?

A

blue precipitate

25
Q

what is the positive result for a test for an ionic solution containing iron (II)?

A

green precipitate

26
Q

what is the positive result for a test for an ionic solution containing iron (III)?

A

brown precipitate

27
Q

what is precipitate?

A

Precipitation is the process of conversion of a chemical substance into a solid from a solution by converting the substance into an insoluble form or a super-saturated solution. When the reaction occurs in a liquid solution, the solid formed is called the precipitate

28
Q

what are two advantages of of instrumental methods compared with chemical tests for identifying chemicals?

A

less time

less chemicals used

29
Q

why is it difficult to identify the metal ions from the colour of the flame, if there are various ions in the compound?

A

because the colours are masked / can only see one colour

30
Q

how would you test for the presence of sulphate ions and what would the positive result be?

A

add barium chloride (solution)
add hydrochloric acid
white precipitate produced

31
Q

how do you test a solution to see if carbonate ions are present?

A

add dilute acid

limewater (turns) cloudy / milky

32
Q

what is the retention factor?

A

distance travelled by substance / distance travelled by solvent ( solvent front )

33
Q

why must the line be in pencil in chromatography?

A

because pencils are insoluble

chemistry (10 decks)

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