Chemical Reactions and Equations — Karnataka (SSLC) Class 10 Science Solutions (Free)
Free step-by-step Karnataka (SSLC) 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: What is a chemical reaction? Give one example.
A chemical reaction is a process where substances combine or decompose to form new substances with different properties. Example: Burning of magnesium in air: 2Mg + O2 = 2MgO (formation of white powder). The reaction is irreversible and produces new chemical bonds.
Q2: Define a balanced chemical equation. Why is balancing necessary?
A balanced equation has equal atoms of each element on both sides, obeying the law of conservation of mass. Balancing is necessary because atoms cannot be created or destroyed; every atom in reactants must appear in products. Example: CH4 + 2O2 = CO2 + 2H2O (balanced).
Q3: Classify chemical reactions into four types with examples.
1. Combination: A + B = AB (C + O2 = CO2). 2. Decomposition: AB = A + B (2H2O = 2H2 + O2 by electricity). 3. Displacement: A + BC = AC + B (Zn + CuSO4 = ZnSO4 + Cu). 4. Double displacement: AB + CD = AD + CB (AgNO3 + NaCl = AgCl + NaNO3).
Q4: What is an exothermic reaction? Give two examples.
An exothermic reaction releases heat energy to surroundings. Examples: 1) Combustion of fuels (burning coal, candle wax). 2) Neutralization (HCl + NaOH = NaCl + H2O releases heat). Temperature of surroundings increases; reaction feels warm to touch.
Q5: Define oxidation and reduction with examples.
Oxidation = loss of electrons or addition of oxygen (or removal of hydrogen). Reduction = gain of electrons or removal of oxygen (or addition of hydrogen). Example: 2Cu + O2 = 2CuO. Here Cu is oxidized (loses electrons) and O2 is reduced (gains electrons); this is a redox reaction.
Q6: What is the difference between a physical change and a chemical change?
Physical change: no new substance formed; reversible; only state, shape, or size changes (melting ice, crushing chalk). Chemical change: new substance formed; usually irreversible; bonds break/form (burning paper, rusting iron, digestion). Chemical changes release or absorb energy.
Q7: Identify the type of reaction and balance: Fe + O2 = Fe2O3.
Type: Combination (two simple substances form one compound). Balancing: Count Fe (2 on right, need 2 on left), count O (3 on right, so need 3/2 O2). Multiply by 2: 4Fe + 3O2 = 2Fe2O3. This is also a redox reaction (Fe oxidized, O reduced).
Related
- NCERT Solutions: Chemical Reactions and Equations — the CBSE version of this same topic.
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