Of the following anions, Br^-, CO3^2-, Cl^-, I^-, NO3^-, NO2^-, PO4^3-, SO4^2-,
ID: 484906 • Letter: O
Question
Of the following anions, Br^-, CO3^2-, Cl^-, I^-, NO3^-, NO2^-, PO4^3-, SO4^2-, SO3^2-, list those ions that meet the following criteria.
1.) Gives a precipitate with Ag^+ ion that is insoluble in HNO3.
Answer: Br^-, Cl^-, I^-
2.) Is involved in an oxidation-reduction reaction as part of a confirmation reaction.
Answer: CO3^2-
3.) Gives a precipitate with Ba^2+ ion that is soluble in HNO3.
Answer: CO3^2-, PO4^3-
4.) Evolves a gas when acid is added.
Answer: CO3^2-, NO3^-, NO2^-
5.) Releases an odorous gas as a product.
Answer: NO3^-, NO2^-
6.) Does not produce a precipitate in any of the following classification or confirmatory reactions.
Classification Reaction 1: Formation of insoluble salts, such as BaCO3, BaSO4, BaSO3, Ba3(PO4)2
Classification Reaction 2: Formation of volatile products when H3O^+ ion is added to such anions as CO3^2-, NO2^-, SO3^2- ions
Classification Reaction 3: Formation of insolube silver salts, such as AgBr, AgCl, AgI
Sulfate Ion Confirmatory Reaction: Na2SO4 dissolved in water, then add BaCl2 solution, then add HNO3
Sulfite Ion Confirmatory Reaction: Na2SO3 dissolved in water, then add H2SO4
Nitrate Ion Confirmatory Reaction: NaNO3 dissolved in FeSO4, then add H2SO4
Nitrite Ion Confirmatory Reaction: NaNO2 dissolved in water, then add H2SO4
Carbonate Ion Confirmatory Reaction: Na2CO3 placed in water, then add H2SO4.water
Phosphate Ion Confirmatory Reaction: Na3PO4 dissolved nitric acid, then add (NH4)2MoO4
Halide Ion Confirmatory Reaction: NaCl dissolved in water, then add chlorine water, then add CH2Cl2
Answer: SO4^2-
Are these answers correct? Any help would be grealy appreciated!
Explanation / Answer
The following scheme of classification of anions has been found to work well in practice; anions are divided into four groups on the basis of their reactions with dilute hydrochloric acid and of the differences of solubilities of their barium and silver salts.
The four groups of anions and the characteristics of these groups are as follows:
Group 1
Visible change, gas evolution and/or formation of a precipitate, with dilute hydrochloric acid. Ions of this group are carbonate, silicate, sulphide, sulphite,and thiosulphate.
Group 2
The anions of this group do not react with hydrochloric acid, but form precipitates with barium ions in neutral medium. Ions of this group are sulphate,phosphate, fluoride,and borate
Group 3
Anions of this group do not react either with dilute hydrochloric acid, or with barium ions in neutral medium. However, they form precipitates with silver ions in dilute nitric acid medium. Anions of this group are chloride, bromide, iodide,and thiocyanate
.Group 4
Common anions, which do not react with reagents of the previous groups,form the last group of anions, which includes nitrite,nitrate and chlorate ions.
Once the anion is found, its presence should be verified by other, characteristic reactions.
(1) Group I anions
Add to the solution an excess of dilute HCl. If there is no change, follow
(2)If a white precipitate or/and gas liberation is observed, one of the following anions
may present: CO32, SiO32, S2, SO32, S2O32.
White, gelatinous precipitate without the liberation of any gas:SiO32present
White precipitate with the liberation of SO2. The gas is tested with a filter paper
moistened with potassium iodate and starch solution.
blue coloration:
S2O32 present.
No precipitate, only gas liberation is observed.
Then test the gas with filter paper moistened with lead acetate solution.
black coloration:S2 present
Test the gas with filter paper moistened with potassium iodate and starch solution.
blue coloration:SO32 present
Introduce the gas into baryta or lime water:
white precipitate:CO32present
Group II anions
Neutralise the solution and add BaCl2 solution. If there is no change follow
3)A white precipitate may result if SO42, PO43, F, or BO33 was originally present. Filter the precipitate, and add HCl solution.
precipitate is not soluble:
SO42 present Add concentrated sulphuric acid to the precipitate or to the original solid sample, and warm the test tube:test-tube acquires a greasy appearance:F present
Add concentrated sulphuric acid and ethanol to the precipitate or to the originalvsample in a porcelain basin and ignite the alcohol:green-edged flame:BO33present
Take a fresh sample and add ammonium molybdate reagent.yellow, crystalline precipitate:PO43 present
(3) Group III anions
Acidify the solution with dilute nitric acid and add AgNO3 solution. If there is no change, follow
(4)Examine the precipitate.
A yellow and yellowish white precipitate indicates Iand Br, respectively.
To a fresh sample, add 1-2 ml carbon tetrachloride and chlorine water dropweise, and shake it intensively:violet organic layer, which turnscolourless with excess chlorine water:Ipresent
reddish-brown organic layer, which turns yellow with excess chlorine water: Br present
A white precipitate may be caused by Clor SCN.
To a fresh sample add FeCl3 solution:blood-red coloration:SCN present
Apply the chromyl chloride test: positive test:Cl present
(4) Group IV anions
One of the following ions may present: NO2, NO3, or ClO3.
Acidify a fresh sample with acetic acid, add sulphanilic acid and -naphthylamine reagents:red coloration:NO2present
Acidify a fresh sample with acetic acid, add sulphanilic acid and -naphthylamine reagents and zinc chips:red coloration:NO3present
Add zinc chips to a fresh sample, filter the solution after a couple of minutes, acidify with dilute nitric or sulphuric acid and add AgNO3 solution to the filtrate:
white precipitate:ClO3 present
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.