Car exhaust contribute a lot to air pollution. And also contribute to global warming by releasing carbon dioxide and water vapor. Global warming is not from exhaust heat (some contribute) but from the fact that carbon dioxide and water absorb heat from the sun and from heat radiating from the ground.
In this experiment we want to detect water vapor and carbon dioxide coming from car exhaust. The source of water and carbon dioxide is from the combustion of gasoline in the engine cylinder. Gasoline is a mixture of hydrocarbons. Hydrocarbons are carbon chains with attached hydrogen atoms. In the image the carbon atom is gray and the white hydrogen atom.
Gasoline and oxygen enter the cylinder and sparks burn the mixture. Sparks begin disconnection of gasoline molecules and oxygen molecules. Oxygen begins to combine with carbon atoms to form carbon dioxide (CO2) and oxygen also combines with hydrogen atoms to form water (H2O). Both of these reactions release energy. Some energy begins to break other gasoline molecules, which in turn allows more oxygen to combine by liberating carbon and hydrogen atoms. In an instant trillions of gasoline molecules are destroyed and now live water and carbon dioxide.
All the energy released from the breakdown of gasoline molecules and joined with oxygen creates carbon dioxide and high pressure water vapor in the engine cylinder. Once this pressure is used to push the bottom cylinder and keep the car running, the hot gas is released to the exhaust system shown below.
In the picture above, the exhaust manifold is the first set pipe that combines the gas released from the cylinder into one pipe. Then forwarded to the Muffler to reduce the explosion of sound coming from gasoline exploded in the cylinder. A catalytic converter (not shown) is before the Muffler and converts unburned gasoline into carbon dioxide and water. Gas comes out of the tail pipe. In this tail pipe where it will be taken to detect moisture.
Carbon Dioxide Detection:
Below will show how to detect carbon dioxide by measuring the pH of the solution before and after it is exposed to carbon dioxide in the exhaust.
Carbon dioxide either emerging from the tail of a car pipe or out of a soda fountain machine nozzle equally reacts equally to water. When water vapor and carbon dioxide are combined, they form a compound called carbonic acid. Or the so-called “carbonation” or “carbonated.” Carbonic acid is what makes carbonic beverage carbonated. It is acidic because two hydrogen atoms (small white balls) come loose. When the hydrogen atom comes off, it leaves one and only the back electrons, which make the hydrogen positively charged.
In your mouth a free hydrogen atom (H+) gives your appetite a feeling of bitterness. The hiss you feel or see is a reversing reaction (going from carbonic acid to CO2 and water). When carbon dioxide becomes acid when it reacts with water, we can use acid to neutralize the basic solution. Alkaline or base opposite of acid.
Lime water is the name of a mineral known as lime (a chemical called calcium oxide / CaO). When chalk (CaO) is added to water, it becomes calcium hydroxide [Ca(OH)2]. The picture below shows what looks like calcium hydroxide. In water the OH– (hydroxide) breaks away. The black minus sign represents an extra electron hydroxide that releases calcium. Hydroxide neutralizes H+ acid. Or you can say otherwise, “acid neutralizes hydroxide., When neutralization occurs, OH– and H+ combine to form water.
This image shows what happens when the flue gas reacts with lime water. The hot CO2 gas and water vapor come from the exhaust pipe (top).
1) The CO2molecule enters the water molecule and combines to form carbonic acid (H2CO3).
2) Hydrogen on carbonic acid releases leaving their electrons behind and becomes H+ ions (a circle with plus sign). H+ ions are attracted by appropriately wearing OH– ions (hydroxide ions).
3) The combination forms water.
4) Carbon with oxygen atom 3 is called carbonate. It has a negative 2 charge because hydrogen leaves their electrons behind. Negative carbonate (CO3)2 is attracted to positively charged calcium ions (Ca2+) Together they form a powder called calcium carbonate which is also known as lime, which can create a cloudy water display.
Carbon Dioxide Detection Using Dyes
A compound called phenolphthalein a material commonly used in the laboratory to show when a solution changes from acid to base or vice versa. The above has been shown carbon dioxide neutralize lime water. When that happens the phenolphthalein solution will change from pink to colorless.
In this experiment we need to place 3 milliliters (3 mL) of distilled water into a 10 mL measuring cup on the left. To pour into a 10 ml measuring cup, the aquades are poured onto a new plastic bottle first into a 10 ml measuring cup.
Aquades bottle are enough to hold about 30 ml of water, so the aquades in the glass is enough to fill the aquadest bottle. After pouring should keep in mind a few drops are poured.
Add 3 ml aquadest (distilled water) water to the measuring cup. Measuring cups are seen closely to see where the 3 ml mark is.
Create a standard lime water tube. Lime water is water that has the maximum amount of calcium hydroxide dissolved in it. This is about 0.1% w / v (meaning 0.1 grams of calcium hydroxide in 100 ml water). This is a weak base solution.
Use a plastic pipette equipped with ml scale from the kit used to transfer 1 mL of lime water to a measuring cup. Measuring glass should be read close to 4 mL because there is already 3 mL of water in it. Then a solution of lime water is about 25% strength of normal lime water. We can use the full strength of lime water for this experiment, but it is better if it is weaker because the car’s exhaust will neutralize faster.
Now we can pour 4 mL of lime water which is diluted from the measuring cup to the 50 mL beaker glass.
Add two or three drops of phenolphthalein solution to a beaker. We will see a purple pink color appear. That means phenolphthalein changes color because it is in a weak base solution. If the solution does not turn purple pink, then it is possible that the lime water has been neutralized by carbon dioxide (CO2) in the air. That can happen if the seal for the test tube is not tight enough. If you do not see the color, just take a few grains of baking soda from the test tube labeled “Sodium bicarbonate (baking soda)” and add to the solution and stir. That should make the solution turn purple. If not, add a little more baking soda. Take a picture of a beaker glass with a solution that shows a purple pink color.
Take the beaker to the exhaust of the vehicle. Start the vehicle and hold 50 mL glasses somewhat close to the exhaust pipe (not burning fingers).
If our theory is true, carbon dioxide is a by-product of gasoline and will produce carbonic acid in water in a glass. That will start neutralizing calcium hydroxide (lime water) or baking soda if we add it.
Approximately 30 seconds later the pink color dimmer. This is because hydrogen ions (H+) derived from carbonic acid are made to neutralize hydroxide ions in lime water.
Then after another 30 seconds and the pink color disappears. Apparently, carbon dioxide has simply entered water and carbonated water with carbonic acid. The acid (hydrogen ion = H+) is neutralized all the hydroxide ions (OH– ) and forms water (H2O). What remains is calcium ions and carbonate ions. These combine to form calcium carbonate, which is chalk.
Take a picture of the glass after carbon dioxide from the exhaust causes the pink phenolphthalein to become colorless.