Qualitative detection of nitrogen sulphur phosphorus and halogens, quantitative analysis and empirical molecular formula calculations - One Line Questions
1.
A sample of an organic compound weighing 0.5 g, when subjected to Kjedahl's method, yielded ammonia which required 20 mL of 0.1 M H2SO4 for complete neutralisation. The percentage of nitrogen in the compound is: —
22.4%
2.
In the quantitative estimation of phosphorus, if 0.2 g of an organic compound gives 0.5 g of magnesium pyrophosphate (Mg2P2O7), the percentage of phosphorus in the compound is approximately: —
32.5%
3.
In the Carius method, 0.3 g of an organic compound containing chlorine gave 0.66 g of AgCl. The percentage of chlorine in the compound is approximately (Atomic mass of Ag = 108, Cl = 35.5): —
44.3%
4.
The empirical formula of a compound represents the: —
Simplest whole number ratio of atoms of each element in a molecule
5.
The precipitate of silver halide formed in Carius method is filtered, washed, dried and weighed. This precipitate is: —
AgCl, AgBr, or AgI
6.
In Kjedahl's method, nitrogen is converted to: —
Ammonium sulphate
7.
In the qualitative detection of phosphorus, after oxidation, the solution is acidified with nitric acid and ammonium molybdate is added. The formation of a canary yellow precipitate indicates the presence of phosphorus. This precipitate is: —
Ammonium phosphomolybdate
8.
In the Liebig's method for estimating carbon and hydrogen, the organic compound is burnt in a stream of oxygen. The products are passed through: —
Anhydrous calcium chloride and potassium hydroxide
9.
The sulphuric acid formed in Carius method for sulphur estimation is precipitated as: —
Barium sulphate
10.
The fusion of organic compound with sodium metal is a preliminary step for the detection of which elements? —
N, S, Halogens
11.
A compound contains C, H, and O. Its empirical formula is C3H6O. If its molecular weight is 114 g/mol, what is its molecular formula? —
C6H12O2
12.
The molar mass of an organic compound is 180 g/mol. Its elemental analysis shows C = 40%, H = 6.67%, and O = 53.33%. What is its molecular formula? —
C6H12O6
13.
A compound has the following percentage composition: C = 75%, H = 25%. Its empirical formula is: —
CH3
14.
A compound contains 40% carbon, 6.67% hydrogen and 53.33% oxygen by mass. The empirical formula of this compound is: —
CH2O
15.
If the molecular mass of the compound with empirical formula CH2O is 180 g/mol, its molecular formula is: —
C6H12O6
16.
If the molecular weight of a compound with empirical formula CH3 is 30 g/mol, its molecular formula is: —
C2H6
17.
A pale yellow precipitate is formed when the aqueous extract of the Lassaigne's fused mass is acidified with dilute nitric acid and treated with silver nitrate solution. This indicates the presence of: —
Bromine
18.
A yellow precipitate, insoluble in dilute ammonia but soluble in excess concentrated ammonia, is formed in the Lassaigne's test for halogens. This indicates the presence of: —
Iodine
19.
The ammonium sulphate formed in Kjedahl's method is then distilled with: —
Sodium hydroxide solution
20.
Which of the following tests is used to detect the presence of both nitrogen and sulphur in an organic compound simultaneously? —
Sodium nitroprusside test
21.
When an organic compound containing nitrogen is fused with sodium metal, sodium cyanide is formed. Sodium cyanide is then converted to sodium ferrocyanide by reacting it with: —
Ferrous sulphate solution
22.
If the ratios obtained after dividing by the smallest mole value are not whole numbers, they are multiplied by the smallest integer that makes them: —
Whole numbers
23.
The halogen in Carius method is converted to: —
Silver halide
24.
After calculating the moles of each element, the next step in determining the empirical formula is to divide the mole values by the: —
Smallest mole value
25.
Which of the following is NOT a quantitative method for estimating elements in organic compounds? —
Fehling's test
26.
Which of the following tests is used for the quantitative estimation of sulphur in an organic compound? —
Carius method
27.
In the determination of empirical formula, the percentage composition of each element is first converted into: —
Moles
28.
If the empirical formula mass of a compound is 'E' and its molecular mass is 'M', then the molecular formula is related to the empirical formula by the relation: —
Molecular Formula = (M/E) x Empirical Formula
29.
If an organic compound containing sulphur is fused with sodium, and the aqueous extract gives a violet colour with sodium nitroprusside solution, it indicates the presence of: —
Sulphur
30.
The Liebig's method is used for the quantitative determination of which element in an organic compound? —
Carbon and Hydrogen
31.
In the detection of halogens using Lassaigne's test, if the solution is acidified with dilute H2SO4 instead of dilute HNO3 before adding AgNO3, what would be the result? —
The test would still be positive for halogens
32.
The excess acid remaining after absorbing ammonia in Kjedahl's method is titrated with a standard solution of: —
Sodium hydroxide
33.
For the detection of phosphorus in an organic compound using Lassaigne's test, the organic compound is fused with sodium. The fused mass is extracted with water and then oxidized with an oxidizing agent. Which oxidizing agent is commonly used? —
Sodium peroxide
34.
In Kjedahl's method, the organic compound is heated with concentrated sulphuric acid in the presence of: —
Potassium sulphate and mercury or copper sulphate
35.
When an organic compound containing chlorine is fused with sodium and the extract is acidified with dilute nitric acid, addition of silver nitrate solution gives a white precipitate. This precipitate is: —
Silver chloride
36.
In the Carius method for estimating halogens, the organic compound is heated with concentrated nitric acid and: —
Silver nitrate
37.
The molecular formula of a compound represents the: —
Actual number of atoms of each element in a molecule
38.
Which reagent is used to test for the presence of sulphur in an organic compound using Lassaigne's test? —
Sodium nitroprusside solution
39.
In the Lassaigne's test for halogens, the organic compound is fused with sodium. The fused mass is extracted with water. Which reagent is then added to detect the presence of halogens? —
Silver nitrate solution
40.
When an organic compound containing both nitrogen and sulphur is fused with sodium, and the aqueous extract is treated with sodium nitroprusside, a violet colour is observed. This is due to the formation of: —
Sodium ferric thiocyanate
41.
The Carius tube method is used for the quantitative determination of halogens and sulphur. The Carius tube is made of: —
Quartz
42.
In Lassaigne's test, the formation of a Prussian blue colouration indicates the presence of which element? —
Nitrogen
43.
The Kjedahl's method is used for the quantitative estimation of which element? —
Nitrogen
44.
In the Carius method for estimating sulphur, the organic compound is heated with concentrated nitric acid. The sulphur is oxidized to: —
Sulphuric acid
45.
The liberated ammonia in Kjedahl's method is absorbed in a known excess of: —
Standard acid solution (e.g., H2SO4 or HCl)
46.
In the Lassaigne's test for the detection of nitrogen, sodium metal is fused with the organic compound. The fused mass is then extracted with water. What is the purpose of this extraction? —
To convert the fused sodium cyanide into sodium ferrocyanide
47.
In the quantitative analysis of an organic compound, if the percentage of an element is calculated, it refers to its percentage by: —
Mass
48.
In Liebig's method, the increase in mass of anhydrous calcium chloride tube corresponds to the mass of: —
Water
49.
In Liebig's method, the increase in mass of potassium hydroxide solution corresponds to the mass of: —
Carbon dioxide