31/1/1
📘 SCIENCE
🎯 Max Marks: 80
📄 Questions: 39
⏰ 15 min reading time · 10:15 to 10:30 AM · All questions compulsory
GENERAL INSTRUCTIONS
- ✓ 39 questions · 5 sections A to E · All compulsory.
- ✓ Section A: Q1-20 (MCQ, 1 mark) ·
Section B: Q21-26 (VSA, 2 marks) · 30-50 words - ✓ Section C: Q27-33 (SA, 3 marks) · 50-80 words
- ✓ Section D: Q34-36 (LA, 5 marks) · 80-120 words
- ✓ Section E: Q37-39 (Case study, 4 marks each) · Internal choices
📌 SECTION A · 20 × 1 = 20 MARKS
⚡ Electrolysis
Electrolysis of water is a decomposition reaction. The mass ratio (M_H : M_O) of hydrogen and oxygen gases liberated at the electrodes during electrolysis of water is:
(B) 2:1
(C) 1:2
(D) 1:8
🔍 VIEW ANSWER
✅ ANSWER: (D) 1:8
Mass of H₂ : O₂ = 2 : 16 = 1 : 8.
🔥 Burning
The products formed when Aluminium and Magnesium are burnt in the presence of air respectively are:
(B) Al₂O₃ & MgO
(C) Al₃O₄ & MgO
(D) Al₂O₃ & MgO₂
🔍 VIEW ANSWER
✅ ANSWER: (B) Al₂O₃ and MgO
Aluminium forms Al₂O₃, Magnesium forms MgO.
🧪 pH Scale
The table shows pH values of four solutions A, B, C, D on a pH scale. (A: pH=2, B: pH=7, C: pH=10, D: pH=13). Identify them:
(B) Weak acid, neutral, weak base, strong base
(C) Weak acid, neutral, strong base, weak base
(D) Weak acid, neutral, strong base, strong acid
🔍 VIEW ANSWER
✅ ANSWER: (B) Weak acid, neutral, weak base, strong base
pH 2 = weak acid? Actually pH 2 is strong acid, but option B says weak acid? Given data: A:2 (acid), B:7 (neutral), C:10 (weak base), D:13 (strong base). Option B matches: weak acid? Possibly misprint, but as per key (B) is correct.
⚗️ Reactions
Consider reactions: (i) dil HCl + NaOH, (ii) MgO + dil HCl, (iii) CO₂ + NaOH. It is found that in each case:
(B) Neutral salts formed
(C) H₂ gas formed
(D) Acidic salts formed
🔍 VIEW ANSWER
✅ ANSWER: (A) Salt and water is formed
All are neutralization/acid-base reactions producing salt+water.
🧪 Ionic Compound
Reaction between A (loses e⁻) and B (gains e⁻) forms compound C. Which property will C NOT show?
(B) Highly soluble in water
(C) Weak electrostatic forces between ions
(D) Conducts electricity in molten/aqueous
🔍 VIEW ANSWER
✅ ANSWER: (C) Weak electrostatic forces
Ionic compounds have strong forces.
⚡ Electrolytic Reduction
Metals obtained from molten chlorides by electrolytic reduction are:
(B) Calcium & Magnesium
(C) Aluminium & Silver
(D) Sodium & Iron
🔍 VIEW ANSWER
✅ ANSWER: (B) Calcium and Magnesium
Highly reactive metals like Ca, Mg are extracted by electrolytic reduction of molten chlorides.
🔬 MgO Formation
The formation of magnesium oxide is correctly shown in option:
(B) Mg↔O₂↔Mg⁺↔O₂²⁻
(C) Mg↔O₂↔Mg²⁺↔O₂²⁻
(D) 2Mg↔O₂↔[Mg²⁺₂]²⁺[O₂²⁻]
🔍 VIEW ANSWER
✅ ANSWER: (D)
2Mg + O₂ → 2MgO, ionic representation: 2Mg²⁺ and 2O²⁻.
🧬 Saliva
Less saliva in mouth will affect conversion of:
(B) fats→fatty acids+glycerol
(C) starch→simple sugars
(D) sugars→alcohol
🔍 VIEW ANSWER
✅ ANSWER: (C) starch into simple sugars
Saliva contains amylase that breaks down starch.
🌱 Plant Hormone
Plant hormone whose concentration stimulates cells to grow longer on side away from light:
(B) Gibberellins
(C) Adrenaline
(D) Auxins
🔍 VIEW ANSWER
✅ ANSWER: (D) Auxins
Auxins cause phototropism.
🌸 Bisexual Flower
True statement(s) for a bisexual flower:
(B) (iv) only
(C) (i) and (iii)
(D) (i) and (iv)
🔍 VIEW ANSWER
✅ ANSWER: (C) (i) and (iii)
(i) both stamen and pistil, (iii) self or cross pollination.
🧬 Genetics
Pea plants: RRyy (round green) × rrYY (wrinkled yellow). F₁ seeds will be:
(B) 75% wrinkled green
(C) 100% round yellow
(D) 75% wrinkled yellow
🔍 VIEW ANSWER
✅ ANSWER: (C) 100% round yellow
RrYy → round (dominant) and yellow (dominant).
⚡ Glucose breakdown
Glucose →(a) pyruvate + energy →(b) lactic acid + energy. Sites a and b:
(B) Cytoplasm & O₂ rich muscle
(C) Cytoplasm & Yeast cells
(D) Cytoplasm & O₂ deficient muscle cells
🔍 VIEW ANSWER
✅ ANSWER: (D) Cytoplasm & O₂ deficient muscle cells
Glycolysis in cytoplasm, then anaerobic in muscle cells.
🔍 Mirrors
Mirror X (solar furnace) and Mirror Y (vehicle side mirror). True statements:
(B) (ii) and (iii)
(C) (iii) and (iv)
(D) (i) and (iv)
🔍 VIEW ANSWER
✅ ANSWER: (A) (i) and (ii)
X: concave (real, diminished, at focus); Y: convex (virtual, diminished, erect).
👁️ Eye Defect
Old person: weakening of ciliary muscles & lens flexibility. Defect ‘a’ corrected by lens ‘b’:
(B) presbyopia, bifocal
(C) myopia, concave
(D) myopia, bifocal
🔍 VIEW ANSWER
✅ ANSWER: (B) presbyopia and bifocal lens
Presbyopia due to age, corrected by bifocal.
🌿 Food Chain
Which groups do NOT constitute a food chain?
(B) (i) and (iii)
(C) (ii) and (iii)
(D) (ii) and (iv)
🔍 VIEW ANSWER
✅ ANSWER: (D) (ii) and (iv)
(ii) Plankton→man? wrong order; (iv) grass→snake→wolf→tiger? missing herbivore.
☀️ Solar Energy
Percentage of solar energy NOT converted into food energy by leaves in terrestrial ecosystem:
(B) 10%
(C) 90%
(D) 99%
🔍 VIEW ANSWER
✅ ANSWER: (D) 99%
Only ~1% converted, so 99% not converted.
⚖️ ASSERTION-REASON (Q17-20)
Q17. Assertion (A): Decomposition reactions are generally endothermic.
Reason (R): Decomposition of organic matter into compost is exothermic.
🔍 VIEW ANSWER
Q18. Assertion (A): Human child bears all basic features of human beings.
Reason (R): It looks exactly like parents, showing very little variations.
🔍 VIEW ANSWER
Q19. Assertion (A): No two magnetic field lines cross each other.
Reason (R): Compass needle cannot point towards two directions at intersection.
🔍 VIEW ANSWER
Q20. Assertion (A): Ozone amount began to drop sharply in 1980s.
Reason (R): Oxygen atoms combine with molecular oxygen to form ozone.