Combustion and Flame Test - 7

Rapid combustion is a form of combustion in which large amounts of heat and light energy are released. Candle shows rapid combustion, whereas   cracker   and   white Phosphorous come under explosion and   spontaneous   combustion respectively.

The combustion in which heat, light and sound are produced is known as explosive combustion.

The correct combination is a - 3, b - 4, c - 2, d - 1 (i) Dark inner zone -Unburnt vapours of wax (ii) Blue zone - Complete combustion (iii) Luminous zone ? Partial combustion (iv) Non-luminous zone - Hottest part (no carbon)

The blue zone in L.P.G. flame indicates the hottest zone where complete combustion takes place.

Natural gas consists of methane, ethane, propane etc., of which methane forms major composition of about 95%.

The Bergius Process is a very simple process for converting brown coal completely into crude oil. It was invented by Dr. Friedrich Bergius. In this process, brown coal, also known as lignite is powdered and mixed with heavy oil and heated with hydrogen under high pressure of about 200-250 atm. and a temperature of about 748 K in the presence of iron oxide as catalyst. The vapours on condensation give a liquid resembling crude oil. This is called synthetic petrol, which on fractional distillation gives petrol (gasoline).

(i) Wood ? 17000 to 22000 kJ/kg (ii) Coal ? 25000 to 33000 kJ/kg (iii) Petrol ? 45000 kJ/kg (iv) Natural gas ? 50000 kJ/kg                 The correct order of the increasing order of calorific values is: (ii), (iii), (i), (iv).

When a fuel (carbon) undergoes incomplete combustion, carbon monoxide is formed. It is a poisonous gas and fatal, if inhaled.

Combustion is burning of a substance in the presence of oxygen. During this process heat energy is released, it is therefore an oxidation and exothermic reaction.