Table of Contents
Important: Chemical Reaction and Equation Questions Class 10th
1. Why should we clean a magnesium ribbon before burning it in the air?
Answer: We should clean the magnesium ribbon to get rid of any oxide layer on it. This layer can stop the magnesium from burning well. By cleaning it, we expose fresh magnesium, which helps it burn brighter and more completely, creating a bright white flame and more magnesium oxide.
2. Why do we put paint on iron objects?
Answer: We put paint on iron objects mainly to protect them. Iron can easily rust when it comes into contact with moisture and air. Rust is a flaky, brown substance that can weaken the iron and cause it to break down over time. By painting the iron, we create a protective layer that keeps water and air away from the surface, which helps prevent rust from forming.
In addition to protecting against rust, paint can also make iron objects look nicer. For example, things like fences, furniture, and tools often look more appealing when they are painted in bright colors or even just a nice clean finish. This can be important for both homes and businesses, as well as for aesthetic reasons.
Moreover, painting can help increase the lifespan of iron items. When they are well-maintained and protected with paint, they can last many years without needing to be replaced. So, by taking the time to paint iron objects, we are not only keeping them safe from rust but also making them look better and ensuring they last longer.
3. What is an exothermic reaction?
Answer: An exothermic reaction is a chemical reaction that gives off energy, usually as heat or light. In these reactions, the products have less energy than the starting materials, which makes the surroundings warmer.
Example: A simple example is burning methane gas:
When methane (CH₄) reacts with oxygen (O₂), it produces carbon dioxide (CO₂) and water (H₂O), along with heat. So, the reaction looks like this:
CH₄+2O₂→CO₂+2H₂O+heat
This means burning methane releases heat into the air.
4. What is an endothermic reaction?
Answer: An endothermic reaction is a chemical reaction that takes in energy from its surroundings. In these reactions, the products have more energy than the starting materials, which can make the surroundings cooler.
Example: A well-known example is photosynthesis:
In this process, plants take in sunlight, carbon dioxide (CO₂), and water (H₂O) to make glucose (C₆H₁₂O₆) and oxygen (O₂). The reaction looks like this:
6CO₂+6H₂O+energy→C₆H₁₂O₆+6O₂
This means plants need energy from sunlight to make their food.
5. Why is respiration considered an exothermic reaction?
Answer: Respiration is called an exothermic reaction because it releases energy into the environment. This energy is essential for our bodies to function properly.
During respiration, glucose, which is a type of sugar that we get from food, reacts with oxygen from the air. This reaction takes place in our cells and produces carbon dioxide and water as byproducts. The main point is that this process releases energy, which our bodies need for various activities, such as moving, growing, and keeping our organs working.
Example: The chemical reaction for respiration can be written like this:
C₆H₁₂O₆+6O₂→6CO₂+6H₂O+energy
In this equation, glucose (C₆H₁₂O₆) and oxygen (O₂) combine to produce carbon dioxide (CO₂), water (H₂O), and energy.
When we take in oxygen, our cells convert glucose into energy. The energy released from this process is used for everything we do, like running, thinking, and even just staying warm. This is why respiration is important for all living things, and it’s why we often describe it as an exothermic reaction—because it gives off energy that our bodies can use!
6. What is a redox reaction? Explain with example?
Answer: A redox reaction, short for a reduction-oxidation reaction, is a type of chemical reaction where electrons are transferred between two substances. In this process, one substance loses electrons (gets oxidized), while the other gains electrons (gets reduced). This exchange of electrons is what makes the reaction happen.
Key Concepts:
- Oxidation: This is when a substance loses electrons. We say it gets oxidized.
- Reduction: This is when a substance gains electrons. We say it gets reduced.
Examples:
- Burning Hydrogen: A simple example is when hydrogen gas burns in oxygen to make water: 2H₂+O₂→2H₂O₂
In this reaction, hydrogen (H₂) loses electrons and is oxidized, while oxygen (O₂) gains electrons and is reduced. - Rusting Iron: Another example is rusting. When iron comes into contact with oxygen and moisture, it turns into rust:
4Fe+3O₂+6H₂O→4Fe(OH)₃
Here, iron (Fe) loses electrons and gets oxidized, while oxygen (O₂) gains electrons and gets reduced.
In summary, redox reactions are important because they involve the transfer of electrons, leading to changes in substances. These reactions are key in many everyday processes, like how we generate energy and how metals corrode.
7. Oil and fat-containing food items flushed with nitrogen? Why?
Answer: Oil and fat-containing food items are flushed with nitrogen to keep them fresh and prevent spoilage. Nitrogen is a gas that doesn’t react with food. By replacing the oxygen in the packaging with nitrogen, it helps stop the food from going bad or becoming stale. This process also helps prevent the growth of bacteria and mold, making the food last longer. Overall, using nitrogen helps maintain the quality of oil and fat-rich foods for a longer time.
8. What is a precipitation reaction?
Answer: A precipitation reaction is a type of chemical reaction where two solutions combine to form an insoluble solid, called a precipitate. This solid separates from the liquid and can often be seen as cloudy or gritty material in the solution.
How It Works: When certain ions in the solutions react with each other, they form a compound that does not dissolve in water. This compound falls out of the solution and settles at the bottom or forms a cloudy mixture.
Example: A common example of a precipitation reaction is when you mix silver nitrate (AgNO₃) and sodium chloride (NaCl) solutions. The reaction produces silver chloride (AgCl), which is a white precipitate:
AgNO₃+NaCl→AgCl↓+NaNO₃
In this reaction, the silver chloride forms as a solid that can be seen in the solution.
In summary, precipitation reactions involve the formation of a solid from two liquids and are important in various fields, including chemistry, environmental science, and medicine.
9. What are the factors affecting the rate of a reaction?
Answer: Several factors can influence how fast a chemical reaction occurs. Here are the main ones:
- Concentration: When you increase the concentration of reactants (the substances that react), the reaction usually happens faster. This is because there are more particles in the same space, which means they bump into each other more often.
- Temperature: Higher temperatures make reactions go faster. When its warmer, particles move quicker, leading to more collisions and more chances for the reaction to occur.
- Surface Area: For solid materials, breaking them into smaller pieces or using a powder can speed up the reaction. More surface area means more particles can react at the same time.
- Catalysts: Catalysts are special substances that speed up a reaction without getting used up. They help reactants change into products more easily.
- Pressure: For reactions that involve gases, increasing the pressure can help the reaction happen faster. Higher pressure pushes gas molecules closer together, which leads to more collisions.
- Nature of Reactants: Different substances react at different speeds. Some chemicals are more reactive than others, which affects how quickly they will react.
In summary, the speed of a reaction can be affected by how concentrated the reactants are, the temperature, the size of solid pieces, the presence of catalysts, the pressure for gases, and the types of substances involved. Understanding these factors helps improve chemical reactions.
10. Write differences between displacement and double displacement reactions?
Answer: The differences between displacement and double displacement reactions:
| Feature | Displacement Reaction | Double Displacement Reaction |
|---|---|---|
| Definition | A reaction where one element replaces another in a compound. | A reaction where two compounds exchange parts to form two new compounds. |
| Types | Can be single (one element displaces another) | Involves two compounds exchanging ions |
| Example | Zinc displacing copper in copper sulfate: Zn+CuSO4→ZnSO4+Cu | The reaction between sodium sulfate and barium chloride: Na₂SO4+BaCl₂→BaSO4+2NaCl |
| Energy Change | May be exothermic or endothermic | Often involves formation of a precipitate |
| Occurrence | Common in metals and halogens | Common in ionic compounds in solution |
11. What is a chemical equation? Explain with example?
Answer: A chemical equation is a way to show what happens during a chemical reaction using symbols and formulas. It tells us what the starting materials (reactants) are and what the end products are.
Example:
Let’s look at the burning of methane, which is a common example:
Chemical Equation: CH₄+2O₂→CO₂+2H₂O
Breakdown of the Example:
- Reactants:
- CH₄ (methane)
- O₂ (oxygen)
- Products:
- CO₂ (carbon dioxide)
- H₂O (water)
Explanation:
- The arrow (→) shows that the reactants turn into products.
- The numbers in front of the formulas (like the “2” in front of O₂ and H₂O) tell us how many molecules are involved in the reaction.
- In this reaction, one molecule of methane combines with two molecules of oxygen to create one molecule of carbon dioxide and two molecules of water.
Chemical equations are important because they help us understand what happens in a reaction and show that matter is conserved—meaning nothing is lost or created during the reaction.
12. What is corrosion?
Answer: Corrosion is the process where metals slowly break down or get damaged because of chemical reactions with their surroundings. This often happens when metals come into contact with things like moisture, air, acids, or salt.
Key Points:
- How It Happens: Corrosion typically occurs when metals react with oxygen and water. For example, when iron is exposed to these elements, it forms rust, which is a reddish-brown substance that makes the metal weaker.
- Common Examples:
- Rusting: The most well-known example of corrosion is rusting. When iron or steel is left outside and gets wet, it can start to rust if it’s not protected. This is why you often see rusty cars or fences.
- Other Metals: Corrosion can happen to other metals too. For instance, copper can develop a green coating called patina when it corrodes, while aluminum can form a layer of white powdery substance.
- Impact of Corrosion:
- Weakening Structures: Corrosion can make metal structures, like bridges and buildings, less safe because it weakens the metal over time. This can lead to accidents or failures if not addressed.
- Costly Repairs: Dealing with corrosion can be expensive. Fixing or replacing corroded metal parts in buildings, vehicles, and machinery can cost a lot of money.
- Prevention: To protect metals from corrosion, various methods can be used, such as painting, coating with special materials, or using alloys that are less prone to corrosion. Regular maintenance can also help prevent damage.
In summary, corrosion is a natural process that causes metals to deteriorate due to environmental factors. Understanding corrosion and taking steps to prevent it is important for maintaining metal objects and structures, ensuring they last longer and remain safe to use.
13. What is rancidity?
Answer: Rancidity is the process that makes food, especially fats and oils, go bad and develop an unpleasant smell or taste. This occurs when the fats in the food break down due to exposure to air, light, or moisture.
Key Points:
- Causes: Rancidity is mainly caused by oxidation, which is a chemical reaction that happens when fats react with oxygen. It can also be influenced by heat and light.
- Types of Rancidity:
- Oxidative Rancidity: This is the most common type, where fats react with oxygen, leading to off-flavors and odors.
- Hydrolytic Rancidity: This occurs when water breaks down fats, often resulting in a soapy taste. This can happen in foods that have been improperly stored or exposed to moisture.
- Effects: Rancid food is not only unappetizing but can also be harmful to health. Consuming rancid oils or fats can lead to digestive issues or other health problems.
- Prevention: To prevent rancidity, it’s important to store fats and oils in a cool, dark place, keep them tightly sealed, and use them within their recommended time frame. Some antioxidants can also be added to food to help slow down the rancidity process.
In summary, rancidity is a process that makes fats and oils spoil, causing them to smell and taste bad. Understanding rancidity and how to prevent it is essential for keeping food fresh and safe to eat.
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