The short answer is no, gold by itself is not an alloy, gold is a pure element. However, due to pure gold ’s (24K) softness, it is often alloyed with other base metals to alter its hardness, along with other properties, so that it may be used to make certain products. This is done when making gold jewelry.

Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties.It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.
Brass is similar to bronze, another alloy containing copper that uses tin in place of zinc; both bronze and brass may include small proportions of a range of other elements including arsenic, lead, phosphorus, aluminum, manganese, and silicon.

The correct answer is Option D.

Potassium dichromate is a powerful oxidizing agent in acidic medium. In the presence of dilute sulphuric acid, it furnishes 3 atoms of nascent oxygen.

The correct answer is option D
An interstitial compound is a compound that is formed when an atom with a small enough radius sits a hole in a metal lattice
They are usually transitional elements
Eg: Tic, Mn₄ N, Fe₃ H, TiH₂ etc.
Main Characteristics:-
·    High melting points than metals
·    They are much harder
·    They become chemically inert
·    They become less malleable
So, the answer is (a), (b), (c) .
 

An aqueous solution of  [Ti(H₂ O)₆ ]³⁺  by absorbing greenish-yellow component of white light, d-d transition takes place and the aqueous solution appears purple as the purple is the complementary colour of greenish yellow.

The correct answer is C
When an alkali is added to an orange red solution of dichromate it forms chromate.
For example:
K₂ Cr₂ O₇  + 2KOH ➡2K₂ CrO₄  +  H₂ O  

The correct answer is Option A.
In acidic medium;
K₂ Cr₂ O₇ →Cr2(SO₄ )₃
  +6          +3
Change in the oxidation number of one Cr atom =6 −3=3.
Change in the oxidation number of two Cr atoms =2 ×3=6.
The equivalent mass of K₂ Cr₂ O₇  
= Formula mass of K₂ Cr₂ O₇ /
Total change in the oxidation number of Cr

= 294 / 6

​= 49
 

The correct answer is option C
Oxidation of nitrites in presence of potassium permanganate results in formation of: Oxidation of nitrites in presence of potassium permanganate results in formation of nitrates (NO^-₃ ).

The correct answer is Option A.

The Mn-containing products from redox reactions depend on the pH. Acidic solutions of permanganate are reduced to the faintly pink manganese(II) ion (Mn²⁺ ) and water. In neutral solution, permanganate is only reduced by three electrons to give manganese dioxide (MnO² ), wherein manganese is in a +4 oxidation state.

The correct answer is Option C
Only d orbitals accept the lone pair of electrons during complex formation. Their absence means that the atom will not be able to accept the lone pair of electrons and the complex will not be formed.