qualitive analysis

Question 1

whats the test for anions

Answer 1

we test for carbonates
sulfates
and halides

Question 2

whats the test for the presence of carbonates

Answer 2

carbonates react with acids to form CO2 gas

Question 3

What’s the equation for carbonate testing

Answer 3

2H+ + CO3^2- ———> CO2 + H2O

Question 4

what happens in the test of carbonates

Answer 4

if you see bubbles the unkown compound could be a carbonate

Question 5

What do you do to prove that the gas is CO2

Answer 5

bubble gas through limewater - a saturated aqueous solution of calcium hydroxide Ca(OH)2
Carbon dioxide reacts to form a fine white precipitate of calcium carbonate which turns lime water cloudy
CO2(g) + Ca(OH)2(aq) ——> CaCO3(s) + H2O(l)

Question 6

What’s the test based on gases for anions

Answer 6

carbonate test

Question 7

what is the test based on precipitate for anions

Answer 7

sulphate test

Question 8

what happens in the sulphate test

Answer 8

most sulphates are soluble in water but barium sulfate BaSO4 is very insoluble in water. The formation of a white precipitate of barium sulfate is the basis for the sulfate test, in which barium ions are added to the solution of an unknown compound

Question 9

Show the ionic equation of the sulphate test

Answer 9

Ba2+(aq) + SO4^2-(aq) ——> BaSO4(s)

Question 10

what happens if you put barium chloride or barium nitrate instead of barium ions

Answer 10

you can carry out a halide test when using barium nitrate
with barium chloride you are introducing chloride ions to your solution

Question 11

what happens in a halide test

Answer 11

most halides are soluble but silver halides are insoluble .
Aqueous silver ions react with halide ions to form precipitate’s of silver halides

Question 12

whats the general equation of halide tests

Answer 12

Ag+(aq) + X-(aq) —–> AgX(s)

Question 13

what do you do in halide test

Answer 13

1) add aq silver nitrate AgNO3 to an aq solution of a halide
2)the silver halide percipitates are different colours
3) add aq ammonia to test

Question 14

what colours are the silver halide percipitates

Answer 14

Fluorides produce no precipitate
Chlorides produce a white precipitate
Ag+(aq) + Cl- (aq)  AgCl(s)
Bromides produce a cream precipitate
Ag+(aq) + Br- (aq)  AgBr(s)
Iodides produce a pale yellow precipitates

Question 15

what is the sequence of tests for anions

Answer 15

carbonate
sulphate
halides

Question 16

why is the carbonate test first

Answer 16

because in the carbonate test you add dilute nitric acid and are looking for effervescence of CO2 gas
neither sulphate or halide produces bubbles with dilute nitric acid. The carbonate test can be carried out without the possibility of an incorrect conclusion
If the test produce no bubbles then no carbonate ion is not present you may proceed to the next test

Question 17

whats the next test

Answer 17

Sulfate test you added solution containing Ba2+(aq) ions and are looking for a white precipitate of BaSO4
Barium carbonate, BaCO3 is white and insoluble in water. So if you carry out a sulfate test on a carbonate you will get a white precipitate too. Therefore its important to carry out the carbonate test first than sulfate when you know that no carbonate is present

Question 18

Why is the Halide test last

Answer 18

in the halide test you add a solution containing Ag+(aq) ions as AgNO3(aq) and are looking for a precipitates.
Silver carbonate AgCO3 and silver sulfate Ag2SO4, are both insoluble in water and will form as precipitates in this test. It is therefore important to carry out the halide test last after carrying carbonate and sulfate test to rule out thosepossibilites

Question 19

what are the test for cations+

Answer 19

test for ammonium ion NH4^+

Question 20

what happens in the test for ammonium ions

Answer 20

when heated heated together aqueous ammonia ions and aqueous hydroxide ions react to form ammonia gas NH3
NH4^+(aq) + OH-(aq) —–> NH3 (g) + H2O(l)

Question 21

how is the test of ammonium ions carried out

Answer 21

1)Aqueous sodium hydroxide ,NaOH is added to a solution of an ammonium ion
2)Ammonia gas is produced. You are unlikely to see gas bubbles as ammonia is very soluble in water
3)The mixture is warmed and ammonia gas is released
4)You may able to smell ammonia but its easy to test with gas with moist indicator paper. Ammonia is alkaline and its presence will turn the paper blue

Question 22

Barium chloride is soluble in water compared to the electrical conductivities of solid and aqueous barium chloride

Answer 22

Barium chloride does not conduct electricity when solid and because it has ions which are fixed ( in lattice)
Barium chloride conducts when aqueous solution because it has mobile ions

Question 23

What is barium chloride used for

Answer 23

To test for sulfates and produce white percipitate

Question 24

Name an apparatus to seperate two liquid layers present at the end of an experiment

Answer 24

Separating funnel

Question 25

What do experimental results tell you about the carbon halogen bond enthalpy

Answer 25

Decrease down the group so chlorine- carbon atoms are the strongest

Question 26

How could students modify their hydrolysis experiment so it could be completed in less time

Answer 26

By heating the test tube in water bath