sc25, quantative analysis: tests for ions (paper 2)

Question 1

what is the flame test

Answer 1

test for metal ions

Question 2

what happens during the flame test

Answer 2

dip the clean loop in a solution of the ions and hold at the edge of a blue flame, which will change colour

Question 3

what’s a precaution you should take during the flame test

Answer 3

• clean the flame test loop in acid each time
• rinse with water
• check it’s clean with the flame

Question 4

what colour is lithium in the flame test

Answer 4

red

Question 5

what colour is sodium in the flame test

Answer 5

yellow

Question 6

what colour is potassium in the flame test

Answer 6

lilac

Question 7

what colour is calcium in the flame test

Answer 7

orange-red

Question 8

what colour is copper in the flame test

Answer 8

blue-green

Question 9

what happens during the hydroxide test

Answer 9

the sample solution is placed in a test tube and a few drops of dilute sodium hydroxide solution are added

Question 10

what colour is copper in the hydroxide test

Answer 10

blue

Question 11

what colour is iron (II) in the hydroxide test

Answer 11

green

Question 12

what colour is iron (III) in the hydroxide test

Answer 12

brown

Question 13

how do you test for sulfate ions

Answer 13

• add dilute hydrochloric acid then barium chloride solution
• white precipitate of barium sulfate forms

Question 14

how do you test for carbonate ions

Answer 14

• add acid
• bubbles of carbon dioxide forms

Question 15

how to test for chloride ions

Answer 15

• add dilute nitric acid then silver nitrate solution
• white precipitate

Question 16

how to test for bromide ions

Answer 16

• add dilute nitric acid then silver nitrate solution
• cream precipitate

Question 17

how to test for iodide ions

Answer 17

• add dilute nitric acid then silver nitrate solution
• yellow precipitate

Question 18

how to test for ammonium ions

Answer 18

• add sodium hydroxide solution
• heat it
• ammonia is produced

Question 19

how do you test for ammonia gas

Answer 19

• the reaction produces water + ammonia
• test for the gas by:
• damp red litmus paper turning blue
• hydrogen chloride gas (from concentrated hydrochloric acid) reacts with ammonia to form ammonium chloride

Question 20

describe what instrumental methods of analysis does

Answer 20

use machines to detect and analyse substances

Question 21

what are the three improved things intrumental methods offer over simple chemical tests

Answer 21

• sensitivity
• accuracy
• speed

Question 22

how is sensitivity improved in instrumental methods than chemical methods

Answer 22

they can detect and analyse very small amounts of different substances

Question 23

how is accuracy improved in instrumental methods than chemical methods

Answer 23

they can measure amounts of different substances very accurately

Question 24

how is speed improved in instrumental methods than chemical methods

Answer 24

they carry out each analysis quickly, and the machine can run all the time

Question 25

what can the data from a flame photometer tell us

Answer 25

• identify the metal ions present in the sample by comparing the spectrum with a reference spectrum from a known substance
• determine the concentration of ions in a solution using a calibration curve