Which of the following is a tough, porous and black substance, and almost a pure form of carbon?

Coke

The correct answer is option 1. Coke.

Here's why:

Coke is a tough, porous, and black substance produced by heating coal in the absence of air. It is almost pure carbon, with very few impurities remaining. This makes it ideal for various industrial applications, including:

Fuel in steelmaking: Coke serves as a fuel source and reducing agent in blast furnaces for extracting iron from iron ore.

Production of other materials: Coke can be further processed to produce graphite, activated carbon, and other carbon-based materials.

Bitumen is a viscous, black, and sticky hydrocarbon mixture found in natural deposits. While it contains carbon, it's not a pure form and has a different consistency and application compared to coke.

Coal tar is a dark, viscous liquid byproduct of coal distillation. It's a complex mixture of various organic compounds and not primarily composed of carbon.

Coal gas is a mixture of flammable gases produced during the heating of coal. It's not a solid material like the other options.

Therefore, based on the characteristics of being tough, porous, black, and almost pure carbon, coke is the correct answer.