Oxygen Content of Air

Oxygen Content of Air

Rozelia Fayard

Pearl River Community College

Abstract

In this experiment, the percent of oxygen in air was found experimentally by using an oxidation reaction that reacts with oxygen and air in a contained volume and measuring the decrease in gas volume that occurred. Using the Ideal Gas Law, the volume of water sucked into the graduated cylinder is the amount of oxygen used from the air. This amount out of the total air volume decreased produced the percent of oxygen in air, which was 22.7%. The theoretical value of oxygen in air is about 21%, so there was a percent error of 8.1%, likely due to escaped gas.

Introduction/Purpose

Oxygen is imperative for life’s process. Oxygen is a very important element because we need it to live. It is a part of the air people breathe and the water people drink. Many living things need oxygen to live. To calculate how much oxygen is in the air and environment around us we use a very common chemical reaction. Oxidation is a chemical reaction when Iron converts to rust.

4Fe + 3O2 → 2Fe2O3.[pic 1]

In a chemical equation, the reactants are the substances that goes through a change in a chemical reaction. The yield is the arrow that is a transition from reactants to products. The products are what the reactants changed into after going through the chemical reaction.

Normally this chemical reaction takes a great amount of time, but fortunately there are catalysts. A catalyst is something that speeds up a chemical reaction. For this lab the catalyst is acetic acid, or vinegar. The vinegar makes it a better environment for the iron to react faster. In this reaction, the steel wool (iron source) will be fluffed up to increase surface area to make a more efficient and faster chemical reaction.

In the experiment we will measure how much oxygen is used from the oxidation by making a vacuum. A vacuum is where the atmospheric pressure decreases below its surrounding pressure. As the steel wool converts to rust, it uses oxygen from the atmosphere. We can calculate how much oxygen is used by measuring the vacuum formed by the iron converting to rust.

Materials

• Eye protection
• Gloves
• Tweezers
• Ruler
• Steel Wool
• Paper Boat
• Triple Beam Balance or Electronic Scale
• Ring Stand with Clamp
• Timer
• 50 mL Beaker
• 35 mL Beaker
• 35 mL Graduated Cylinder (one that fits into the 35 mL beaker)
• Acetic Acid (0.3 M)
• Water

Procedure

1. Put on your eye protection and gloves
2. Tare out weight of paper boat and place approximately 0.75g of steel wool and record the weight onto the table chart. Once measured fluff the steel wool to increase the surface area.
3. Measure out 35 mL of acetic acid and pour into 50 mL beaker. [keep in a well-ventilated area] Using tweezers submerge the steel wool into acetic acid. Let sit for one minute, then remove with tweezers. Meanwhile measure in cm how tall is the graduated cylinder.
4. Once removed from the acid, ensure the steel wool is still fluffed. [Do not rinse off the steel wool] Then quickly place into the bottom of a clean 35 mL graduated cylinder.
5. Overturn the graduated cylinder onto the 35 mL beaker and fasten the graduated cylinder onto the ring stand’s clamp. Once clamped add water to the beaker until the water goes just over the lip of the graduated cylinder. [Do not let water drop below the graduated cylinder.] Gently add water to the beaker if need. This reaction may take up to 20 minutes.
6. When there is no more water being sucked up into the graduated cylinder, measure how many cm the water traveled up the cylinder.
7. Repeat steps 2-6 for run #2

Data/Results

Discussion

Conclusion