Chemical Tests

Question 1

how to test for H2?

Answer 1

squeaky pop - lighted splint in sample and pop heard if h2 present

Question 2

how to test for O2 gas?

Answer 2

place a glowing splint in the sample
if splint relights o2 is present

Question 3

how to test for Cl2 gas?

Answer 3

litmus paper in sample
cl2 gas will make it turn red then white

Question 4

how to test for CO2?

Answer 4

turns limewater cloudy

Question 5

How to test for carbonates?

Answer 5

add dilute acid
bubble through limewater
if it turns cloudy co2 present

Question 6

how to test for halides?

Answer 6

acidify using dilute nitric acid - to remove carbonates
then add silver nitrate solution
chl ions - white ppt
br ion - cream ppt
iodide ions - yellow ppt

Question 7

how to test for sulfate ions?

Answer 7

acidify using dilute HCl
add barium chloride
if white ppt of barium sulphate occurs there is SO4 2- ions

Question 8

what do these metal cations form using aq sodium hydroxide?

Al3+ , Ca 2+ , Mg 2+
Cu 2+ , Fe2+ , Fe 3+

Answer 8

aluminium calcium and mg are white ppt
fe 2+ is green
fe 3+ is brown
Cu 2+ is blue

Question 9

What colour do these cations turn in a flame test?
Li
Na
K
Ca
Cu

Answer 9

crimson red
yellow orange
lilac
red orange
green

Question 10

How to test for water?

Answer 10

using Cu(11) SO4

anhydrous Cu 2 sulfate is white but when water is added it form hydrated copper 2 sulfate and will turn blue