Vijay Kumar Ojha

Both the assertion (A) and the reason (R) are correct.

Assertion (A) provides a balanced chemical equation for the action of steam on iron. This equation is balanced because the same number of atoms of each element is present on both sides of the reaction, which is a requirement of the Law of Conservation of Mass.

Reason (R) is also correct. The Law of Conservation of Mass states that the total mass of substances in a chemical reaction remains constant; no atoms are created or destroyed. In other words, the number of atoms of each element on the reactant side of the equation must be equal to the number of atoms of the same element on the product side. Balancing a chemical equation is a way to ensure that this law is upheld in a chemical reaction.

So, in this case, the assertion (A) and the reason (R) are both valid and related to the fundamental principle of the conservation of mass in chemical reactions.

Photosynthesis is a crucial biological process with significant importance for life on Earth. Its primary significance lies in the following aspects:

1. **Energy Conversion:** Photosynthesis is the process by which green plants, algae, and some bacteria convert sunlight into chemical energy stored in glucose (sugar) molecules. This stored energy is essential for the survival and growth of these organisms and serves as the foundation of the food chain in ecosystems. It is the basis for virtually all life on Earth, as it provides energy for heterotrophic organisms (those that cannot produce their own food).

2. **Oxygen Production:** During photosynthesis, plants release oxygen as a byproduct. This oxygen is vital for the respiration of most living organisms, including humans. It replenishes the Earth's atmosphere with oxygen, maintaining the necessary levels for aerobic respiration and the survival of aerobic organisms.

3. **Carbon Dioxide Uptake:** Photosynthesis involves the uptake of carbon dioxide from the atmosphere. This plays a critical role in regulating the Earth's carbon cycle, helping to mitigate the greenhouse effect and climate change. By absorbing carbon dioxide and converting it into organic molecules, photosynthetic organisms contribute to the reduction of atmospheric CO2 levels.

4. **Food Production:** Photosynthesis is the primary means by which plants produce their own food. It is the source of carbohydrates and other organic compounds that make up their structure. These plant-based foods serve as the foundation of human and animal diets, providing the necessary nutrients and energy for life.

5. **Biodiversity:** Photosynthetic organisms form the basis of terrestrial and aquatic ecosystems. They support diverse ecosystems by providing food and energy for a wide range of organisms. Their presence and productivity determine the overall health and diversity of ecosystems.

The balanced chemical equation for photosynthesis is as follows:

**6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2**

In this equation:
- 6 molecules of carbon dioxide (6 CO2) are taken up from the atmosphere.
- 6 molecules of water (6 H2O) are absorbed from the roots.
- In the presence of light energy, these molecules are converted into glucose (C6H12O6) and oxygen (6 O2).
- Glucose is stored as energy or used for growth, and oxygen is released into the atmosphere.

This chemical equation summarizes the overall process of photosynthesis, which takes place in the chloroplasts of plant cells and is essential for the sustainability of life on Earth.

(a) The law followed in balancing a chemical equation is the Law of Conservation of Mass. It states that the total mass of substances in a chemical reaction remains constant, meaning that the number of atoms of each element must be the same on both sides of the equation.

(b) To balance the chemical equation: Na + H3O → NaOH + H2, you need to ensure that the same number of each type of atom is present on both sides of the equation. Here's the balanced equation:

2Na + 2H3O → 2NaOH + H2

Now, the equation is balanced, and the number of atoms of each element is the same on both sides.