Topic 7-Testing For Ions Flashcards
What is a salt
A salt is a substance that consists of two ions, a positive ion- cation and a negative ion- anion
Method of the flame tests for the presence of cation
~ assemble the apparatus and light the Bunsen Burner. Adjust the regulating collar to open the hole on the Bunsen burner and ensure a hot Bunsen flame
~ clean the flame test rod by dipping into concentrated hydrochloric acid
~ hold the flame test rod in the hot Bunsen flame. Repeat until the wire does not produce any colour in the flame.
~ dip the clean flame test rod into the concentrated hydrochloride acid again and dip into a small amount of the unknown solution.
~ place the rod in the Bunsen flame
~ observe the colour of the flame and identify the cation present
~repeat to identify the unknown solution
Flame test for Na+ colour
Yellow
Flame test for K+ colour
Lilac
Flame test for Ba+ colour
Apple green
Flame test for Ca+ colour
Brick red
Flame test for Cu+ colour
Blue/ green
What is a precipitate
A precipitate is an insoluble substance which is sometimes formed when two aqueous solutions are mixed
Identifying cations by using …..
NaOH-
Method of testing for cations using NaOH-
1) . Dissolve one spatula of the salt in a little H20
2) . Place 10cm3 of the solution in a test tube
3) . Add NaOH- solution drop by drop
4) . Observe the colour of the precipitate if one it produced
5) . For any white precipitate that is produced, continue to add NaOH- solution, drop by drop
6) . Observe what happens to the precipitate
What is the colour of the precipitate when MgCl is tested for identifying cations using NaOH- and does it dissolve in excess?And work out the ionic equation
White
No
Mg2+(aq) + 2OH-(aq) —> Mg(OH)2(s)
What is the colour of the precipitate when AlCl is tested for identifying cations using NaOH- and does it dissolve in excess?
And work out the ionic equation
White
Yes
Al3+(aq) + 3OH-(aq) —> Al(OH)3(s)
What is the colour of the precipitate when Zn(ll)Cl is tested for identifying cations using NaOH- and does it dissolve in excess?
And work out the ionic equation
White
Yes
Zn2+(aq) + 2OH-(aq) —> Zn(OH)2(s)
What is the colour of the precipitate when Cu(ll)Cl is tested for identifying cations using NaOH- and does it dissolve in excess?
And work out the ionic equation
Blue
No
Cu2+(aq) + 2OH-(aq) —> Cu(OH)2(s)
What is the colour of the precipitate when Fe(ll)Cl is tested for identifying cations using NaOH- and does it dissolve in excess?
And work out the ionic equation
Green
No
Fe2+(aq) + 2OH-(aq) —> Fe(OH)2(s)
What is the colour of the precipitate when Fe(lll)Cl is tested for identifying cations using NaOH- and does it dissolve in excess?
And work out the ionic equation
Red- brown
No
Fe3+(aq) + 3OH-(aq) —> Fe(OH)3(s)
While testing for halide ions (group VII) we have to use …
Nitric acid —> HNO3
AgNO3
What is the method for testing for halide ions
1) . Dissolve a spatula of the solid in 20cm3 water
2) . Place 5cm3 of the solution in a test tube
3) . Add four drop of HNO3
4) . Add AgNO3 drop by drop
5) . Observe the colour of the precipitate of one is produced
While testing for halide ions and using AgNO3 in the test for NaCl what is the…
~ Halide ion present
~ Colour of the precipitate
~ ionic equation
Cl-
White
Ag+(aq) + Cl-(aq) —> AgCl(s)
While testing for halide ions and using AgNO3 in the test for KBr what is the…
~ Halide ion present
~ Colour of the precipitate
~ ionic equation
Br-
Cream
Ag+(aq) + Br-(aq) —> AgBr(s)
While testing for halide ions and using AgNO3 in the test for NaI what is the…
~ Halide ion present
~ Colour of the precipitate
~ ionic equation
I-
Yellow
Ag+(aq) + I-(aq) —> AgI(s)
If sulphate ions are present a _______ _________ of BaSo4(s) will form when the sample is reacted with ……..
White precipitate
BaCl solution
While testing for sultan ions we have to use…
BaCl
What is the method used if you are testing for sulfate ions
~ dissolve a spatula of the salt in 20cm3 of deionised H20
~ place about 10cm3 of the solution into a test tube
~ add BaCl solution drop by drop
~ observe the colour of the precipitate if one is produced
When testing for sulfate ions using BaCl we test on AlSO4. Is there a sulfate ion present, what is the colour of the precipitate and what is the ionic equation
Yes
White
Ba2+(aq) + SO4,2-(aq)—> BaSO4(s)
When testing for sulfate ions using BaCl we test on MgCl. Is there a sulfate ion present, what is the colour of the precipitate and what is the ionic equation
No
None
No precipitate
When testing for sulfate ions using BaCl we test on NaSO4. Is there a sulfate ion present, what is the colour of the precipitate and what is the ionic equation
Yes
White
Ba2+(aq) + SO4,2-(aq)—> BaSO4(s)
Testing for carbonate CO3,2- ions we use
Limewater
Hydrochloride acid
Acid + metal—>
Salt + H2O + CO2
The method we use to test for carbonate
~ place the solid into a side arm test tube which has a downward delivery tube attached
~ fill a test tube with limewater and place the downward delivery tube in the test tube
~ add 5cm3 of HCl to the side arm test tube and quickly put the bung on
~ if the limewater becomes cloudy/ milky the gas evolved is CO2 and the salt is carbonate
Testing for carbonate by using magnesium carbonate, what reactions will take place?
- bubbles of gas
- solid disappears
- limewater turns cloudy
Testing for carbonate by using magnesium carbonate, what reactions will take place?
- bubbles of gas
- solid disappears
- limewater turns cloudy
