Q18 of 30 Page 1

What are food preservatives? Name two such substances.

A food preservative is a substance or a chemical which is added to food items to prevent their decomposition by microbial growth or by undesirable chemical changes and to prevent its spoilage. Sodium benzoate, sodium nitrite are used as food preservatives.


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16

Describe the following giving the relevant chemical equation in each case:

1. Carbylamine reaction


2. Hofmann’s bromamide reaction.


 17

Complete the following reaction equations:

 19

Copper crystallizes with face centred cubic unit cell. If the radius of copper atom is 127.8 pm, calculate the density of copper metal. (Atomic mass of Cu = 63.55 u and Avogadro’s number NA = 6.02 x 1023 mol-1)
OR
Iron has a body centred cubic unit cell with the cell dimension of 286.65 pm. Density of iron is 7.87 g cm-3. Use this information to calculate Avogadro’s number. (Atomic mass of Fe = 56.0 u)

 20

The electrical resistance of a column of 0.05 M NaOH solution of diameter 1 cm and length 50 cm is 5.55 x103ohm. Calculate its resistivity, conductivity and
molar conductivity.