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H2S: Definition & Lewis Structure

Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

You can not see it nor taste it, but you can certainly smell it a mile away; what a great way to describe the chemical hydrogen sulfide. This lesson is devoted to learning about hydrogen sulfide and detailing its Lewis structure.

What Is Hydrogen Sulfide?

Hydrogen sulfide is best defined as a colorless, flammable gas that contains a smell closely resembling that of rotten eggs. A relatively small chemical, with a molecular weight of 34.1, hydrogen sulfide is commonly found in the environment, both naturally and from human activities.

In its gaseous state, it makes sense that hydrogen sulfide likes to hang around other gasses or mingle in gaseous conditions. This applies to nature, where hydrogen sulfide is commonly found in places such as volcanic gas, petroleum gas (unrefined), and hot springs (Diagram 1). And yes, I know you were thinking, 'What about human flatulence (i.e. gas)?' Glad you asked, because hydrogen sulfide is produced as a by-product from bacteria in our intestines. Of course the only way for our bodies to release hydrogen sulfide, is through. . . well, I'm quite sure you can predict what that bodily outlet might be.

Diagram 1: Where Hydrogen Sulfide Is Released into the Environment
h2s environment

Heavier than air, it is not uncommon to detect the presence of hydrogen sulfide when close to the ground. For example, you can collect samples of hydrogen sulfide in poorly ventilated or enclosed areas near the ground such as: in basements, manholes, and sewer lines (Diagram 1). Hydrogen sulfide is widely used (and produced as a by product) in industry through processes such as the manufacturing of paper products, mining, and asphalt paving.

On a more serious note, it is important to remember that this chemical is very toxic. It surely is not the type of chemical to play around with. Although the symptoms may range from headaches to irritated eyes (at low, chronic exposure), higher exposure can result in death.

Let's look at it this way, if a person sucks in just a small amount of breaths contaminated with hydrogen sulfide, at levels greater than 700ppm, it can be deadly. A very 'smart' chemical compound, the smell of hydrogen sulfide is so strong that your nose can fatigue (at a level as low as 100ppm), causing you to think you no longer smell that stinky foul odor. What a dangerous trickster that chemical can be!

Equally important are the physical properties of hydrogen sulfide. Not only is this chemical highly flammable but corrosive and explosive as well. With an auto ignition temperature of 250C, we can think of this as hydrogen sulfide igniting a fire if you exposed it to a temperature equivalent to a 480 degree oven. Hence, it is highly flammable and explosive. If you encounter hydrogen sulfide in its solid form, it will be yellow in color and resemble a powder like substance.

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