Reaaaaaaally need help with C3 precipitates, plleeeasse anyone?

  • -1 votes

Precipitates, i'm sooo lost. I don't even know any, you may aswell throw flame tests in aswell

Posted Wed 23rd May, 2012 @ 19:29 by Sofia

5 Answers

  • 1 vote

If you want, try and make up a sentence out of the colours.

Flame tests:

Barium, apple green (sick,bleurgh)

Calcium, Brick-red

Lithium, red (love)

Sodium, Yellow (yucky)

Potassium, Lilac (pretty)

Precipitates:

Al3+, Ca2+, Mg2+ - all whiten  CAM 

Cu2+ - Blue 

Fe2+ - Green (to brown)

Fe3+ - Brown (rust red) 

Answered Wed 23rd May, 2012 @ 19:58 by anonymous
  • 1 vote

what you mean remembering them? You could try and create a sentence/rhyme or whatever, but I just try and rember them by going over them:

Precipitates: 

Al3+ , Ca2+ and Mg2+ are ALL WHITE

Cu2+ is BLUE

Fe2+ is GREEN

Fe3+ is BROWN (remember this is just rust)

Flame Tests:

Barium is GREEN

Sodium is YELLOW

Calcium is BRICK RED

Lithium is RED

Potassium is LILAC

you'll also need to know that when testing for things such as iron(II) ions you use sodium hydroxide and that when testing for sulfate ions you use barium chloride etc.. 

try out my quiz i just made  : http://getrevising.co.uk/resources/chemistry_c3_quiz_foundation#quiz

Answered Wed 23rd May, 2012 @ 19:58 by Matthew
  • 1 vote

add sodium hydroxide solution-

  • Mg2+ white preciptate
  • Ca2+ white
  • Al3+ white
  • Cu2+ blue
  • Fe2+ 'dirty' green (turns brown on standing in air for some time)
  • Fe3+ reddish brown  

Al3+ ions redissolve in excess sodium hydroxide whilst Mg and Ca can be distiguished in flame test: Mg-no colour Ca- brick red

add dilute nitric acid and then silver nitrate solution

  • Cl- white precipitate
  • Br- cream
  • I-yellow

add dilute hydrochloric acid then barium chloride solution, if SO42- (sulphate ions) present white precipitate

Thats all I think you need to know about with precipitates!

Answered Wed 23rd May, 2012 @ 20:00 by Dilly
  • 0 votes

Test for carbonate : Add dilute acid

gives white precipitate and turns limewater cloudy

Test for ammonia:

Add NaOH ,gas given off with sharp smell.....turn litmus paper blue (ammonia is given off)

Answered Wed 23rd May, 2012 @ 20:00 by anonymous
  • 0 votes

Thank you soooooo much, you are all such big help!! **

Answered Wed 23rd May, 2012 @ 20:58 by Sofia