testing for group 2 ions Flashcards
step 1.
Four test tubes should be placed in a test tube rack
Around ……drops of 0.1 mol dm-3 barium chloride solution should be added to the first test tube
10
Around …………drops of dilute sodium hydroxide solution (NaOH) should be added to the same test tube
10
step 3 Swirl the test tube carefully to mix well
Continue to add sodium hydroxide dropwise to the test tube, until it is in excess
This should then be repeated in the other test tubes, for calcium bromide solution, magnesium chloride solution and strontium chloride solution
Any observations should be noted down in a suitable results table
The same test as above can also be done using ammonia solution and sulfuric acid solution
LOOk up method
Ammonium
magnesium + white precipitate Mg(OH)2
calcium 2+ no change
barium 2+ no change
strontium 2+ no change
Testing for Ammonium Ions
About 10 drops of a solution containing ammonium ions, such as ammonium chloride, should be added to a clean test tube
About 10 drops of sodium hydroxide should be added using a pipette
The test tube should be swirled carefully to ensure that it is mixed well
The test tube of the solution should then be placed in a beaker of water, and the beaker of water should be placed above a Bunsen burner, so that it can become a water bath
As the solution is heated gently, fumes will be produced
look up method
A pair of tongs should be used to hold a damp piece of red litmus paper near the mouth of the test tube, to test the fumes
The red litmus paper will change colour and become……….. in the presence of ammonia gas
blue
excess sodium hydroxide ions reaction
magnesium + white precipitate Mg(OH)2
calcium 2+ white precipitate Ca(OH)2
barium 2+ no change
strontium 2+ slightly white precipitate Sr(OH)2
excess sulfuric acid
Mg2+ - colourless solution
Ca2+ -slightly white precipitate (CaSO4
Sr2+- White precipitate ( SrSO4
Ba2+- white precipitate (BaSO4
