Principles Related to Practical Chemistry

In the Kjeldahl's method for estimation of nitrogen present in a soil sample, ammonia evolved from 0.75 g of sample neutralized 10 mL of 1 M H2SO4. The percentage of nitrogen in the soil is

1. 37.33
2. 45.33
3. 35.33
4. 43.33

Nitrogen detection in an organic compound is carried out by Lassaigne's test. The blue colour formed corresponds to which of the following formulae?

1. Fe3[Fe(CN)6]2
2. Fe4[Fe(CN)6]3
3. Fe4[Fe(CN)6]2
4. Fe3[Fe(CN)6]3

The Lassaigne's extract is boiled with conc. HNO3 while testing for halogens. By doing so it

1. decomposes Na2S and NaCN, formed
2. helps in the precipitation of AgCl
3. increases the solubility product of AgCl
4. increases the concentration of NO3- ions

In Dumas method of estimation of nitrogen, 0.35 g of an organic compound gave 55 mL of nitrogen collected at 300 K temperature and 715 mm pressure. The percentage composition of nitrogen in the compound would be (aqueous tension at 300 K = 15 mm).

1. 15.45
2. 16.45
3. 17.45
4. 14.45

The best method for the separation of naphthalene and benzoic acid from their mixture is

1. distillation
2. sublimation
3. chromatography
4. crystallisation.

Which of the following is incorrect?

1. FeCl3 is used in detection of phenol.
2. Fehling's solution is used in detection of glucose.
3. Tollens' reagent is used in detection of unsaturation.
4. NaHSO3 is used in detection of carbonyl compound.

In steam distillation of toluene, the pressure of toluene in vapour is

1. equal to pressure of barometer
2. less than pressure of barometer
3. equal to vapour pressure of toluene in simple distillation
4. more than vapour pressure of toluene in simple distillation.