Chemical Reactions and Equations — Maharashtra (SSC) Class 10 Science Solutions (Free)

Free step-by-step Maharashtra (SSC) Class 10 Science solutions for "Chemical Reactions and Equations" — important questions with detailed answers, download PDF for board exam preparation.

Chemical Reactions and Equations — Maharashtra (SSC) Class 10 Science Solutions (Free)

Free step-by-step Maharashtra (SSC) Class 10 Science solutions for "Chemical Reactions and Equations" — important questions with detailed answers, download PDF for board exam preparation.

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Chemical Reactions and Equations — Textbook Questions Answered (7)

Q1: Define chemical reaction and chemical equation. What is meant by balancing?

Chemical reaction: A process in which reactants are transformed into products with breaking and formation of chemical bonds. Chemical equation: A symbolic representation of a chemical reaction using chemical formulas and coefficients. Balancing: Adjusting coefficients so that number of atoms of each element is equal on both sides. Balanced equation shows the correct molar ratios of reactants and products.

Q2: Balance the equation: Fe + O2 -> Fe2O3

Step 1: Count atoms on both sides: Fe: 1 left, 2 right; O: 2 left, 3 right Step 2: Balance Fe: Multiply Fe by 4 and Fe2O3 by 2 -> 4Fe + O2 -> 2Fe2O3 Step 3: Count O: Left has 2, right has 6 (2 x 3). Multiply O2 by 3 Step 4: 4Fe + 3O2 -> 2Fe2O3 Step 5: Verify: Fe = 4 on both sides, O = 6 on both sides. Balanced.

Q3: Classify the following reactions: (1) CaCO3 -> CaO + CO2 (2) H2 + Cl2 -> 2HCl (3) AgNO3 + NaCl -> AgCl + NaNO3

(1) Decomposition reaction: Single reactant breaks into multiple products due to heat. (2) Combination or synthesis reaction: Two reactants combine to form one product. (3) Displacement or double displacement reaction: Ions exchange partners. Ag+ exchanges with Na+, Cl- exchanges with NO3-. AgCl is precipitate (insoluble). All are irreversible reactions in forward direction.

Q4: Define redox reaction. What are oxidation and reduction?

Redox reaction: A reaction in which oxidation and reduction occur simultaneously. Oxidation: Loss of electrons (or gain of oxygen or loss of hydrogen). Reduction: Gain of electrons (or loss of oxygen or gain of hydrogen). Example: 2Cu + O2 -> 2CuO. Here, Cu loses electrons (oxidized), O2 gains electrons (reduced). Oxidizing agent: Substance that causes oxidation (O2). Reducing agent: Substance that causes reduction (Cu).

Q5: Identify oxidation and reduction in: Zn + CuSO4 -> ZnSO4 + Cu

Step 1: Determine oxidation states. Zn: 0 -> +2 (loses 2 electrons, oxidized). Cu: +2 -> 0 (gains 2 electrons, reduced). Step 2: Oxidation occurs at Zn atom (reducing agent). Reduction occurs at Cu atom (oxidizing agent). Step 3: Electrons lost by Zn = electrons gained by Cu = 2 electrons. This is a displacement reaction where more reactive Zn displaces Cu from its compound.

Q6: Balance this equation and identify the redox reaction: H2 + Cl2 -> HCl

Step 1: Unbalanced: H = 2 left, 1 right; Cl = 2 left, 1 right Step 2: Add coefficient 2 before HCl: H2 + Cl2 -> 2HCl Step 3: Check: H = 2 both sides, Cl = 2 both sides. Balanced. Step 4: Redox analysis: H oxidation state: 0 -> +1 (oxidized). Cl: 0 -> -1 (reduced). It's a combination redox reaction where H and Cl are both reducing and oxidizing agents.

Q7: What are exothermic and endothermic reactions? Give examples from combustion and decomposition.

Exothermic reaction: Releases heat energy to surroundings (DeltaH is negative). Example: CH4 + 2O2 -> CO2 + 2H2O (combustion). Used in heating and cooking. Endothermic reaction: Absorbs heat from surroundings (DeltaH is positive). Example: CaCO3 -> CaO + CO2 (decomposition by heat). Requires constant heating. Most combustion reactions are exothermic, most decomposition reactions are endothermic.

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