The following is an experimental account of the preparation of compound B from Phenylamine. 2cm3 of phenylamine are dissolved in 10cm3 of 0.5M hydrochloric acid in a test tube and cooled in an ice bath. 5cm3 of 0.2M sodium nitrate solution cooled to about 5o are added to the solution above and shaken. A salt A, C6H5N2Cl is formed, collected and dried. 1g of salt A is dissolved in 10cm3 of water, cooled and added drop by drop to a cold solution of 0.3g phenol in 5cm3 of 0.1M sodium hydroxide solution. B is precipitated, filtered, dried and the melting point determined. B is further crystallized twice and the melting point taken each time and found to be constant. Questions: (i) Give the name and suggest the colour of the precipitate B. Hence explain why it is necessary to recrystallize B several times. (ii) Why was it necessary to obtain a constant melting point for B?
The following is an experimental account of the preparation of compound B from Phenylamine.
2cm3 of phenylamine are dissolved in 10cm3 of 0.5M hydrochloric acid in a test tube and cooled in an ice bath. 5cm3 of 0.2M sodium nitrate solution cooled to about 5o are added to the solution above and shaken. A salt A,
C6H5N2Cl is formed, collected and dried. 1g of salt A is dissolved in 10cm3 of water, cooled and added drop by drop to a cold solution of 0.3g phenol in 5cm3 of 0.1M sodium hydroxide solution. B is precipitated, filtered, dried and the melting point determined. B is further crystallized twice and the melting point taken each time and found to be constant.
Questions:
(i) Give the name and suggest the colour of the precipitate B. Hence explain why it is necessary to recrystallize B several times.
(ii) Why was it necessary to obtain a constant melting point for B?
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