Answer to Question #91140 in Chemistry for Promise Omiponle

Question

1. A. Fill in the blank space with the suitable answers.
Nitrogen, halogens and sulfur in organic compounds can be detected by performing the ................ test.
Presence of carbon and hydrogen in organic compounds can be detected by heating the organic compounds with .............

B. How will you evaluate the effectiveness of the methods you used to purify the compounds?

2. A. Differentiate between qualitative and quantitative analysis.

B. Identify the suitable methods to separate each of the following mixtures and explain how to separate them
i. Vegetable oil and sugar
ii. Salt and sugar
iii. Benzene and benzoic acid

Answer 1

1. A.

Nitrogen, halogens and sulfur in organic compounds can be detected by performing the 'Lassaigne's test'.

Presence of carbon and hydrogen in organic compounds can be detected by heating the organic compounds with cupric oxide (CuO)

B. The methods for purification of substances are:

1)     Simple crystallisation

2)     Fractional crystallisation

3)     Sublimation

4)     Simple distillation

5)     Fractional distillation

6)     Distillation under reduced pressure

7)     Steam distillation

8)     Azeotropic distillation

9)     Chromatography

2. A.

Qualitative analysis gives the presence or absence of different chemical components in a sample whereas quantitative analysis gives the amount of different chemical components present in a given sample.

B.

i. Vegetable oil and sugar

We add water and dissolve the sugar. Oil should now float above the solution. We heat the sugar solution to supersaturation and crystallise the sugar out.

ii. Salt and sugar

To separate the salt and sugar, first we have mix the salt and water in the alcohol through filtration and then we use evaporation.

iii. Benzene and benzoic acid

We could separate them by distillation. Distillation is the joint process of vapourisation and condensation. We use this method for the purification of liquids which boil without decomposition and contain non-volatile impurities.