Ch 1 Chemical reaction and equation for class 10

Write the balanced chemical equation for the reactions that take place during respiration. Identify the type of combination reaction that takes place during this process and justify the name. Give one more example of this type of reaction

Answer: Ans (i) The carbohydrates that we take in our food are oxidized to carbon dioxide and water. C₆H₁₂O₆ + 6O₂→ 6CO₂ + 6H₂O The carbon of carbohydrates and oxygen combine to form CO₂. (ii) It is an exothermic combination reaction. (iii) Decomposition of vegetable matter into compost is another example of this type of reactio

Why do we store silver chloride in dark-colored bottles?

Answer: Ans Silver chloride is the best example of a light-sensitive chemical compound, and the reaction is an example of a photolytic decomposition reaction. It reacts with light very fast and loses its property by forming chlorine gas and silver. So avoid this silver chloride in dark-colored bottles.

Write one equation each for decomposition reactions in which energy is supplied in the form of heat, light, or electricity.

Answer: Ans a) Thermal decomposition reaction (Thermolysis) Decomposition of potassium chlorate: If heated strongly, potassium chlorate decomposes into potassium chloride and oxygen molecules. This reaction is commonly used for the synthesis of oxygen molecules. 2KClO3 + heat → 2KCl + 3O2 (b) Electrolytic decomposition reaction (Electrolysis)- Decomposition of sodium chloride NaCl : On passing electricity through molten sodium chloride NaCl, it decomposes into sodium and chlorine. 2NaCl—- 2Na + Cl2 (in Electrolysis) (c) Photodecomposition reaction (Photolysis) Decomposition of Hydrogen peroxide- In the presence of light, hydrogen peroxide decomposes into water and oxygen molecules. 2H2O2 + light H2O + O2

What is the difference between displacement and double displacement reactions? Write relevant equations for the above.

Answer: A displacement reaction occurs when a more reactive substance replaces a less reactive substance from its salt solutions. A double displacement reaction occurs when a mutual exchange of metal ions happens between 2 compounds. Example: Displacement reaction Mg + 2HCl → MgCl2 + H2 Double displacement reaction 2KBr + BaI2 → 2KI + BaBr2

Explain the following in terms of the gain of oxygen with two examples each. (a) Oxidation (b) Reduction

Answer: (a) In a chemical reaction when oxygen is added to the element to form its respective oxide, it is the element being oxidized. For Example: 4Na(s) + O2(g) → 2Na2O(s) H2S + O2 → H2O + SO2 (b) In a chemical reaction, it is said to be reduced when oxygen is removed from the compound. For Ex.,: so CuO(s) + H2(g) → Cu(s) + H2O(l) 2HgO → 2Hg + O2(g)