In which of the following industries is Potassium Nitrate (KNO3) commonly used on a commercial scale?

Introduction / Context:

This question tests basic applied chemistry knowledge by asking about a commercial use of Potassium Nitrate, KNO3. Potassium Nitrate is a well known oxidising agent and is widely used in pyrotechnics and fireworks. Awareness of such common industrial applications often appears in general science sections of competitive examinations.

Given Data / Assumptions:

• Potassium Nitrate has the chemical formula KNO3.
• It is a strong oxidising agent and forms part of traditional gunpowder mixtures.
• The options list different industries, including glass, electroplating, fire crackers, leather and textiles.
• The question asks where it is used commercially in a prominent way.

Concept / Approach:

Fireworks and fire crackers require rapid combustion of fuel to create light, sound and coloured effects. Oxidising agents supply oxygen to sustain and accelerate combustion. Potassium Nitrate has long been used for this purpose, historically in gunpowder and modern pyrotechnic compositions. While it has minor uses in other fields, its association with explosives and fireworks is strongest. The approach is to link the chemical behaviour of KNO3 with the industry that relies heavily on such oxidising action.

Step-by-Step Solution:

Verification / Alternative check:

Chemistry references and online resources about pyrotechnics describe compositions where Potassium Nitrate acts as an oxidiser, particularly in black powder and simple rockets. Historical records also show that KNO3, often called saltpetre, was a main component of early explosives. While small amounts of nitrates may appear in other processes, only the fire cracker or fireworks industry consistently relies on high quantities of Potassium Nitrate, which verifies the answer.

Why Other Options Are Wrong:

Glass manufacturing typically uses materials such as silica, soda ash and limestone as main raw materials; nitrates are not a principal component. Electroplating uses metal salts and solutions designed for deposition of metals on surfaces, rather than Potassium Nitrate as a key reagent. Leather tanning relies on vegetable tannins or chromium salts, not KNO3. Textile dyeing involves various dyes and mordants, again without central dependence on Potassium Nitrate. Thus these industries are not the primary commercial users of KNO3 in the way that fireworks manufacturing is.

Common Pitfalls:

Students may be aware that KNO3 has minor or experimental uses in agriculture or food preservation and might overgeneralise to other industries. Some may also guess glass manufacturing because they have seen other metal salts there. The safest strategy is to connect the oxidising function of KNO3 with industries that need rapid burning and explosions, which clearly points to fireworks and fire crackers.

Final Answer:

Potassium Nitrate is used commercially mainly in Fire cracker manufacturing.