What dangerous products does burning hydrocarbon give?

Answer 1

Well, when burning hydrocarbons in complete combustion, the products are Water (H2O) + Carbon Dioxide (CO2). The only potentially dangerous product of complete combustion of hydrocarbons is CO2 in large amounts which some people believe presents a danger of global warming.

However, if you are referring to incomplete combustion then the products are Water (H2O) + Carbon Dioxide (CO2) + Carbon Monoxide (CO) + Soot (C). Now CO is very dangerous and suitably nicknamed the silent killer. It is heavier than air so it sinks to floor level. Also it is invisible to the human eye. It is dangerous because it will bind to the hemoglobin in the red blood cells stopping them from carrying oxygen - which will starve you of oxygen and kill you.

Using hydrocarbons as fuels also presents the problem of fuel that does not burn and enters the atmosphere as a vapor along with the exhausted gases from the fuel that did burn. Unburned gasoline (petrol) vapor, when exposed to sunlight, will form what are called "radicals" which will react with the air to produce ground-level ozone. Ironically while ozone in the high atmosphere helps protect plants and animals (and people) from the harmful effects of UV radiation from the sun, ozone at ground level is destructive of plants and attacks tissue in the lungs of animals.

An additional problem is that we usually burn hydrocarbons with air, not just pure oxygen. Since air is about 78-79% nitrogen (N2), there is plenty of N2 in the flame. The nitrogen also reacts with the oxygen at the high temperatures of combustion (it isn't much prone to the reactions at normal atmospheric temperatures) to form different nitrogen compounds referred to collectively as NOx. The "x" in NOx just means that it could be any one of several numbers - thus it includes NO, NO2, N2O, N4O, NO3, N2O3, N2O4, N2O5, N(NO2)3. N2O is pretty stable in the air but fortunately is only produced in very small amounts. Since N2O is also known as "laughing gas" you can decide for yourself it this is good or bad. NO and NO2 are fairly reactive. NO3 is highly reactive. The other compounds tend to decompose fairly quickly. All of the reactive and decomposing compounds can decompose or react with the atmosphere to form other compounds that are not too friendly to plants, animals, fabrics, metals, and masonry. NO2 is a brown gas and a the primary component of Smog - that brown haze that hangs over some cities.

The original answer incorrectly suggested that CO2 would damage the ozone layer and thus lead to global warming. CO2 has no effect on the ozone layer. Also, the ozone layer has no significant effect on global warming.