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Chemistry > Testing for Ions > Flashcards

Testing for Ions Flashcards

1
Q

what are the precautions to be taken when working with a toxic substance

A

use a fume cupboard
wear protective gloves

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2
Q

what are the precautions to be taken when working with a corrosive substance

A

wear safety goggles
wear protective gloves

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3
Q

what are the precautions to be taken when working with an irritant

A

wear safety glasses
wear protective gloves
use a dust mask

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4
Q

what is the test for chlorine

A

test the gas with damp blue litmus paper, it first turns red and then bleaches

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5
Q

what is the test for ammonia

A

test the gas with damp red litmus paper, it turns blue

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6
Q

what are the different ways of collecting gases

A

collected over water (if the gas is insoluble)
collected by upward delivery (if the gas soluble in water and less dense than air)
collected by downward delivery (if the gas is soluble in water and denser than air0

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7
Q

how do you measure the volume of a gas

A

using a gas syringe

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8
Q

how do you carry out a flame test

A

clean a platinum wire loop using HCL.

Pick up a small amount of the solid using the wire loop

Heat the solid in the edge of a blue bunsen flame/roaring flame

observe and the record the colour of the flame

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9
Q

what are the different colours of positive ions in a flame test

lithium
sodium
potassium
calcium
copper

A

lithium - red
sodium - yellow
potassium - lilac
calcium - orange red
copper - blue green

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10
Q

why is it difficult to identify 2 different ions in a compound using a flame test

A

the two colours would mix together

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11
Q

what are the advantages of instrumental methods of analysis over flame tests

A

more sensitive
more accurate
more rapid

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12
Q

what can a flame photometer do

A

identify the metal ions in a substance and measure the concentrations of metal ions

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13
Q

how is a metal ion in an unknown solution identified

A

matching its spectrum to the spectrum from a known metal ion

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14
Q

why is distilled water used to make the standard solutions rather than tap water

A

tap water contains dissolved metal ions which may interfere with the results

distilled water does not contain metal ions

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15
Q

how is a calibration curve for the concentration of K+ ions produced

A

using standard solutions of K+ ions and a flame photometer

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16
Q

what are the strengths of flame tests

A

they are simple to carry out
do not need expensive equipment

17
Q

what are the weaknesses of flame tests

A

a large amount of sample is needed
cannot identify different metal ions in a mixture
cannot determine the conc of metal ions in a sample

18
Q

what are the strengths of a flame photometer

A

small amount of sample is needed / more sensitive
can identify different metal ions in a substance
accurately determine the conc of metal ions in a sample

19
Q

how can you identify metal ions using metal hydroxide solution

A

a few drops of metal hydroxide solution are added to the solution containing the metal ion

a precipitate of the metal hydroxide is formed

the colour of the precipitate can be used to identify the metal ion

20
Q

what coloured precipitates are formed when sodium hydroxide solution is added to aluminium, calcium, copper, iron 2+ , iron 3+

A

aluminium - white precipitate
calcium - white precipitate
copper - blue precipitate
iron 2+ - green precipitate
iron 3+ - brown precipitate

21
Q

what happens when you add excess sodium hydroxide solution to aluminium ions

A

the white precipitate dissolves to form a colourless solution

22
Q

what is the test for ammonium ions

A

add sodium hydroxide solution to the solution and warm

ammonia gas is produced when the mixture is warmed

test the gas with damp red litmus paper

it goes from red to blue which confirms ammonia

23
Q

what is the test for carbonate ions

A

add dilute HCL to the substance and test the gas produced with limewater.

Fizzing is observed and the limewater turns cloudy

24
Q

what is the test for chloride/bromide/iodide ions

A

add a few drops of dilute nitric acid (to remove any carbonate ions that may be present) then add silver nitrate solution

25
Q

what colour precipitates do chloride/bromide/iodide ions form

A

chloride - white precipitate
bromide - cream precipitate
iodide - yellow precipitate

26
Q

what is the test for sulfate ions

A

add a few drops of dilute HCL then add barium chloride solution, a white precipitate of barium sulfate is formed

Chemistry (21 decks)

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