Question

Which of the following is not a compound?
(A)- Black lead
(B)- White lead
(C)- Red lead
(D)- None of the above

Answer 1

Hint: A compound is made up of atoms of different elements combined together in definite proportions by mass. The composition or ratio of two or more different elements in a compound is always the same. A molecule is made up of atoms of the same element.


Complete step by step solution:
Let us examine all the options one by one.
Black lead
Black lead is another name for graphite. Graphite is a crystalline and thermodynamically the most stable form of carbon. It has a layered structure in which all the carbon atoms are \[s{{p}^{2}}\] hybridized and bonded to other three carbon atoms forming hexagonal rings. Now since, graphite is one of the different forms of elemental carbon (allotropes) and it differs from the other forms of carbon only in physical properties. Hence, graphite only one type of atom, i.e. carbon. Therefore, black lead is not a compound.
White lead
White lead is the most commonly used white pigment used in paints. It is poisonous and insoluble in water. Chemically white lead is a complex salt of lead carbonate and lead hydroxide. Its chemical formula is $2PbC{{O}_{3}}.Pb{{(OH)}_{2}}$. Thus, white lead is a compound containing different elements in definite composition.
Red lead
Red lead is an oxide containing lead in two different oxidation states, i.e. $P{{b}^{2+}}$ and $P{{b}^{4+}}$in 1:1 ratio. Its chemical formula is given as $P{{b}_{3}}{{O}_{4}}$. It is bright red or orange in colour and used as pigment in paints. Since $P{{b}_{3}}{{O}_{4}}$ contains Pb and O bonded together in a fixed ratio by weight, thus it is a compound.
Based on the above discussed characteristics of black, white and red lead, it is clear that white lead and red lead are compounds whereas black lead is not a compound.

Hence, the correct option is (A).

Note: We are most likely to consider all the options as different forms of lead owing to their names. Do not make that mistake. Remember than white lead and red lead are different compounds of lead and are named so because of their colour.