Chemical Reactions and Equations — Class 10 Chemistry NCERT Solutions (Free)
Free step-by-step NCERT solutions for Class 10 Chemistry chapter "Chemical Reactions and Equations" — 10 important questions with detailed answers for CBSE board exam preparation.
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TL;DR: Free step-by-step NCERT solutions for Class 10 Chemistry chapter "Chemical Reactions and Equations" — 10 important questions with detailed answers for…
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Key Questions Covered:
- What are the four main observations that indicate a chemical reaction has tak…
- Balance the following chemical equation and identify the type of reaction: `A…
- What is a decomposition reaction? Explain with an example where heat is used …
- What happens when an iron nail is placed in a copper sulphate solution? Write…
- Define precipitation reaction. Give an example of a precipitation reaction, w…
- Identify the substance oxidised, substance reduced, oxidising agent, and redu…
- + 4 more questions in the full chapter
Solutions Summary:
| Question | Status |
|---|---|
| What are the four main observations that indicate a chemi… | ✓ Solved |
| Balance the following chemical equation and identify the … | ✓ Solved |
| What is a decomposition reaction? Explain with an example… | ✓ Solved |
| What happens when an iron nail is placed in a copper sulp… | ✓ Solved |
| Define precipitation reaction. Give an example of a preci… | ✓ Solved |
| Identify the substance oxidised, substance reduced, oxidi… | ✓ Solved |
Showing 6 of 10 questions
Q1: What are the four main observations that indicate a chemical reaction has taken place? Give one example for each.
A chemical reaction is a process that involves the rearrangement of the molecular or ionic structure of a substance, as opposed to a change in physical form. We can identify a chemical reaction by observing certain changes. The four main observations are:
1. **Change in State:** Reactants might be liquids and products might be gases, or vice-versa.
* **Example:** When a candle burns, solid wax melts (physical change) and then reacts with oxygen to produce carbon dioxide (gas) and water v...
Q2: Balance the following chemical equation and identify the type of reaction: `Al (s) + O_2 (g) \rightarrow Al_2O_3 (s)`
To balance the chemical equation, we need to ensure that the number of atoms of each element is the same on both the reactant and product sides (Law of Conservation of Mass).
The given unbalanced equation is:
`Al (s) + O_2 (g) \rightarrow Al_2O_3 (s)`
**Step 1: List the number of atoms of each element on both sides.**
| Element | Reactant Side | Product Side |
| :------ | :------------ | :----------- |
| Al | 1 | 2 |
| O | 2 | 3 |
**Ste...
Q3: What is a decomposition reaction? Explain with an example where heat is used to carry out the decomposition.
A **decomposition reaction** is a type of chemical reaction in which a single compound breaks down into two or more simpler substances (elements or simpler compounds). These reactions often require energy in the form of heat, light, or electricity to proceed.
**Example using heat (Thermal Decomposition):**
When calcium carbonate (limestone) is heated, it decomposes into calcium oxide (quicklime) and carbon dioxide gas.
**Equation:**
`CaCO_3 (s) \xrightarrow{\text{Heat}} CaO (s) + CO_2 (g)`
**...
Q4: What happens when an iron nail is placed in a copper sulphate solution? Write the balanced chemical equation and identify the type of reaction.
When an iron nail is placed in a copper sulphate solution, the following observations and chemical changes occur:
**Observations:**
1. The blue colour of the copper sulphate solution starts to fade and gradually turns greenish.
2. A reddish-brown layer gets deposited on the surface of the iron nail.
**Explanation:**
Iron is more reactive than copper. According to the reactivity series, a more reactive metal can displace a less reactive metal from its salt solution. In this case, iron (Fe) di...
Q5: Define precipitation reaction. Give an example of a precipitation reaction, write its balanced chemical equation, and mention the colour of the precipitate formed.
**Precipitation Reaction:**
A precipitation reaction is a type of double displacement reaction where two aqueous solutions react to form an insoluble solid product called a precipitate. This precipitate separates from the solution, often appearing as a cloudy or solid substance settling at the bottom.
**Example:**
When an aqueous solution of Barium Chloride (`BaCl_2`) is mixed with an aqueous solution of Sodium Sulphate (`Na_2SO_4`), a white precipitate of Barium Sulphate (`BaSO_4`) is formed a...
Q6: Identify the substance oxidised, substance reduced, oxidising agent, and reducing agent in the following reaction: `CuO (s) + H_2 (g) \rightarrow Cu (s) + H_2O (l)`
Let's analyse the given reaction step-by-step to identify oxidation, reduction, and the agents involved.
`CuO (s) + H_2 (g) \rightarrow Cu (s) + H_2O (l)`
**Step 1: Understand Oxidation and Reduction in terms of Oxygen/Hydrogen.**
* **Oxidation:** Gain of oxygen or loss of hydrogen.
* **Reduction:** Loss of oxygen or gain of hydrogen.
**Step 2: Identify what happens to each reactant.**
* **For CuO:** It loses oxygen to become `Cu`.
`CuO \rightarrow Cu` (Loss of oxygen)
Therefore...
Showing 6 of 10 questions. Visit the full page for complete solutions.