Question

(a) Taking hydrogen peroxide, how would you prepare oxygen in the laboratory ? (b) What is the role of manganese dioxide in the preparation of oxygen ? (c) Write the balanced chemical equation for the above chemical reaction. (d) Why is hydrogen peroxide preferred in the preparation of oxygen gas? le) Why is oxygen collected by downward displacement of water ? (H) What happens when a glowing splinter is introduced in a jar containing oxygen ? (g) What happens when oxygen gas is passed through alkaline pyrogallol solution ?​

Answer 1

1. To make oxygen in the laboratory, hydrogen peroxide is poured into a conical flask containing some manganese(IV) oxide. The gas produced is collected in an upside-down gas jar filled with water. As the oxygen collects in the top of the gas jar, it pushes the water out.
2. Manganese dioxide catalyzes the decomposition of hydrogen peroxide to oxygen and water. Since manganese dioxide is a catalyst, it is not consumed in the reaction.
3. Count the numbers of atoms of each kind on both sides of the equation to be sure that the chemical equation is balanced.
4. H2O2 is preferred for lab preparation of oxygen because of following reasons. No heating is required. The rate of evolution of oxygen (O2) is moderate and under control. H2O2 is a safe chemical.
5. Oxygen is collected by the downward displacement of water because it is only slightly soluble in water and is less dense than water. Therefore, it can be collected over water without the fear of excessive dilution.
6. The splint is introduced to the gas sample that has been trapped in a vessel, when it comes into contact with oxygen the splint catches fire. When a glowing splinter is introduced in a jar containing oxygen, the glowing splinter rekindles but the gas does not catch fire.
7. When in alkaline solution, it absorbs oxygen from the air, turning brown from a colourless solution. It can be used in this way to calculate the amount of oxygen in air, notably via the use of the Orsat apparatus.

Answer 2

Answer:

• To make oxygen in the laboratory, hydrogen peroxide is poured into a conical flask containing some manganese(IV) oxide. The gas produced is collected in an upside-down gas jar filled with water. As the oxygen collects in the top of the gas jar, it pushes the water out.
• Manganese dioxide catalyzes the decomposition of hydrogen peroxide to oxygen and water. Since manganese dioxide is a catalyst, it is not consumed in the reaction.