Question

Which is not a basic flux:
A. Silica
B. Limestone
C. Calcite
D. Quick lime

Answer 1

Hint:Flux is the substance which is actually added to remove the gangue from the concentrated ore in its molten state and the substance which is formed with flux is known as Slag.

Complete step-by-step answer:Flux is the substance which is actually added to separate the gangue from the concentrated ore in its molten state and the substance which is formed with flux is known as Slag. Slags are generally silicates.
Acidic Flux:
$ \Rightarrow Si{O_2} + CaO \to CaSi{O_3}$
The above reaction shows the acidic flux which is used to remove the basic impurities. Some more acidic flux are Borax, HCl etc.
Basic Flux:
$ \Rightarrow Si{O_2} + MgO \to MgSi{O_3}$
The above reaction shows the basic flux which is used in removing acidic impurities. Examples of basic flux are limestone, CaO etc.

Additional Information :
Silica is actually the name given to a minerals group which is composed of silicon & oxygen, which are the two most abundant elements in the earth's crust. Silica is mainly found in the crystalline state and very rarely in an amorphous state. It is composed of 1 atom of silicon and 2 atoms of oxygen which results in the chemical formula of SiO2.
Limestone is actually a carbonate sedimentary rock that is mainly composed of the skeletal fragments of marine organisms like coral, foraminifera, and molluscs. Its main materials are the minerals calcite and aragonite, which are various crystal forms of calcium carbonate (CaCO3).
Calcite is a rock-forming mineral along with a chemical formula of CaCO3. It is very common and can be found throughout the world in sedimentary, metamorphic, and igneous rocks. Many geologists consider it to be a "ubiquitous mineral" - one which is found everywhere. Calcite is the main constituent of limestone and marble.
Quicklime is known for its wide range of uses, involving in the formation of iron and steel, paper and pulp production, also the treatment of water and flue gases and in the mining industry.

Hence, Option (A) Silica is correct and it is not a basic flux.

Note:Observe the hint and relation between the given options as each have their own workings and applications. The substance which is formed with flux is known as Slag and they are generally silicates.