Class 10 Science Test Paper Chapter 1 AND 5(Half) | CBSE Board | Detailed Solutions & Marking Scheme
VEDANT SKILL ASSESSMENT SERIES
ACADEMIC YEAR 2026-27
CLASS: X (CBSE) | TIME: 1 Hour | MAX. MARKS: 30 SUBJECT: SCIENCE (Chemical Reactions & Equations & Life Processes)
GENERAL INSTRUCTIONS:
Read all questions carefully before answering. — Misreading the question and then blaming the paper will not increase your marks.
Show proper steps wherever required. — “Sir, answer toh yahi aana tha” is not an accepted mathematical method.
Write neatly and clearly. — If your handwriting requires a decoder machine, checking may become an adventure.
Manage your time wisely. — Spending 45 minutes on one question and calling the rest “optional” is not a strategy.
If you do not know the answer, you may cry silently. — Loud crying, emotional speeches, and negotiations for hints are strictly prohibited.
SECTION A (Objective Type Questions)
[7 × 1 = 7 Marks]
Q1. When solid Lead Nitrate powder is heated strongly in a dry test tube, a clear brown colored gas 'X' is evolved along with a yellow residue 'Y'. Identify gas 'X' and specify the correct type of chemical reaction occurring here: A. X = NO2, Thermal Decomposition reaction B. X = O2, Oxidation reaction C. X = N2, Combination reaction D. X = NO, Double Displacement reaction
Q2. An experimental setup for the electrolysis of water is monitored. The volume of gas collected over one electrode is exactly twice the volume of gas collected over the other electrode. Which option correctly identifies the gases and their respective electrodes? A. Double volume gas = Oxygen at Cathode; Single volume gas = Hydrogen at Anode B. Double volume gas = Hydrogen at Cathode; Single volume gas = Oxygen at Anode C. Double volume gas = Oxygen at Anode; Single volume gas = Hydrogen at Cathode D. Double volume gas = Hydrogen at Anode; Single volume gas = Oxygen at Cathode
Q3. During a high-intensity exercise session, an athlete experiences severe painful muscular cramps. This condition arises due to the anaerobic breakdown of glucose inside cytoplasm, which leads to the direct deposition of: A. Ethanol + Carbon dioxide + Energy B. Lactic acid + Energy C. Pyruvate + Water D. Carbon dioxide + Water + Energy
Q4. A student sets up an experiment to study the necessity of a specific gas during photosynthesis. Two potted plants are kept under sealed glass bell jars. Jar 'A' contains a small beaker filled with Potassium Hydroxide (KOH) pellets, while Jar 'B' does not. After leaving them in sunlight, the leaves of plant 'A' fail to show a blue-black coloration during the subsequent iodine starch test. The pellet compound KOH was placed to absorb: A. Oxygen gas B. Carbon dioxide gas C. Water vapor D. Nitrogen gas
Q5. Consider the following balanced chemical reaction sequence:
3MnO2 + 4Al → 3Mn + 2Al2O3 + Heat
Which of the statements below correctly characterizes the electronic redox shifts happening in this active process?
A. Aluminium is oxidized and Manganese Dioxide acts as the reducing agent.
B. Aluminium is reduced and Manganese Dioxide acts as the oxidizing agent.
C. Aluminium is oxidized and Manganese Dioxide acts as the oxidizing agent.
D. Manganese is oxidized and Aluminium acts as the oxidizing agent.
For Question 6 and Question 7, a statement of Assertion (A) is followed by a statement of Reason (R). Choose the correct option from the following:
A. Both A and R are true, R is correct explanation of A
B. Both A and R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true
Q6. Assertion (A): The inner wall lining of the small intestine contains millions of tiny finger-like projections called villi. Reason (R): Villi significantly increase the effective inner surface area for the ultra-efficient absorption of digested nutrient molecules.
Q7. Assertion (A): Silver chloride turns grey when exposed to sunlight in an open porcelain dish. Reason (R): The presentation of gray color is due to the decomposition of silver chloride into silver metal and chlorine gas by photons.
SECTION B (Very Short Answer Questions)
[4 × 2 = 8 Marks]
Q8. Write down a balanced chemical equation for each of the following real-life processes, explicitly showing state symbols: [2] (i) Respiration as a biochemical energetic breakdown mechanism inside cells. (ii) Rusting of iron when exposed to atmospheric oxygen and moisture.
Q9. Distinguish clearly between the structural mechanisms of 'Breathing' and 'Cellular Respiration' based on cellular locus and energy outputs. [2]
Q10. A bright shiny brown-colored element 'X' on being heated in air turns black in color to form a compound 'Y'. If hydrogen gas is passed over this heated black material 'Y', the original shiny brown surface configurations of 'X' reappear. Identify 'X' and 'Y' and write both balanced chemical equations. [2]
Q11. State the exact location and physiological functions of the following digestive secretions in the human alimentary canal: [2] (i) Hydrochloric Acid (HCl) secreted inside the stomach. (ii) Bile juice secreted by the liver and stored in the gall bladder.
SECTION C (Short Answer Questions)
[2 × 3 = 6 Marks]
Q12. Design an experiment to demonstrate that Carbon Dioxide is given out during the process of respiration in germinating seeds. Describe the mandatory technical precautions and observations regarding the water level movement inside the delivery tube. [3]
Q13. Translate the following verbal statements into balanced chemical equations and classify the underlying reaction type for each: [3] (i) Iron nails dipped in blue Copper Sulphate solution turn fade green, separating out reddish-brown copper particles. (ii) Barium Chloride solution mixed with Sodium Sulphate solution results in an immediate thick white settling solid mass. (iii) Slaked lime paste applied to interior walls reacts slowly with atmospheric components to form a shiny crust.
SECTION D (Long Answer Question)
[1 × 5 = 5 Marks]
Q14. Answer the following questions based on human physiology and respiratory interfaces: (a) Draw a clear, neat schematic diagram tracking the pathway of air from nostrils down to the functional respiratory surface area of human lungs. Label the Trachea, Bronchi, and Alveoli clearly. [2] (b) Explain how the microscopic structural layout of Alveoli is optimally adapted to maximize the gaseous exchange rates between the environment and matching blood capillaries. [2] (c) Why is a specialized respiratory pigment required for oxygen transport in large multicellular organisms like humans instead of relying purely on simple diffusion? Name the pigment. [1]
SECTION E (Case Study Based Question)
[1 × 4 = 4 Marks]
Q15. Read the following real-world biochemical industrial passage carefully and answer the questions that follow:
Thermite Reactions and Metabolic Energy Analogies: In mechanical metallurgy, joining cracked railway tracks requires the local generation of high-temperature liquid metal without traditional furnaces. This is accomplished via a 'Thermite Reaction', where fine iron oxide powder reacts with aluminum powder. Once ignited, the highly exothermic displacement reaction releases enough heat to melt the displaced iron, which flows into the structural cracks. Similarly, in biological systems, metabolic pathways break down nutrients like glucose through stepwise oxidation. While a thermite reaction releases its energy uncontrollably as light and heat, living cells use controlled cellular enzymes to capture released redox energy in small packets, storing it within stable chemical high-energy bonds known as ATP. Both processes are exothermic redox events, but their kinetics and energy-trapping efficiencies differ based on the environmental medium.
(a) Write the complete, balanced chemical equation representing the industrial Thermite Reaction between Iron(III) Oxide (Fe2O3) and Aluminium powder. [1]
(b) Identify which species is being oxidized and which is acting as the oxidizing agent in the industrial thermite process described above. [1]
(c) Elaborate on how the energy release profile of biological respiration in living beings differs from the rapid chemical combustion seen in thermite or candle fire. Highlight the role of ATP. [2]
VEDANT SKILL ASSESSMENT SERIES
ACADEMIC YEAR 2026–27
CLASS: X (CBSE) | SUBJECT: SCIENCE
Chemical Reactions & Equations & Life Processes
SOLVED ANSWER KEY WITH MARKING SCHEME
Max. Marks: 30
SECTION A – OBJECTIVE TYPE QUESTIONS
[7 × 1 = 7 Marks]
Q1.
Reaction:
2Pb(NO3)2 (s) → 2PbO (s) + 4NO2 (g) + O2 (g)
Brown gas = Nitrogen dioxide (NO2)
Yellow residue = Lead oxide (PbO)
Reaction type = Thermal decomposition
Correct Answer: A. X = NO2, Thermal Decomposition reaction
Marking Scheme: 1 Mark
Q2.
Electrolysis of water:
2H2O → 2H2 + O2
Hydrogen is produced in double volume and collected at Cathode.
Oxygen is produced at Anode.
Correct Answer: B
Marking Scheme: 1 Mark
Q3.
During anaerobic respiration in muscles:
Glucose → Lactic acid + Energy
Lactic acid accumulation causes cramps.
Correct Answer: B. Lactic acid + Energy
Marking Scheme: 1 Mark
Q4.
KOH absorbs Carbon dioxide.
Without CO2, photosynthesis does not occur.
Hence no starch forms.
Correct Answer: B. Carbon dioxide gas
Marking Scheme: 1 Mark
Q5.
Reaction:
3MnO2 + 4Al → 3Mn + 2Al2O3 + Heat
Aluminium loses oxygen → Oxidized
MnO2 gains electrons → Oxidizing agent
Correct Answer: C
Marking Scheme: 1 Mark
Q6.
Assertion = True
Small intestine contains villi.
Reason = True
Villi increase surface area for absorption.
Reason correctly explains assertion.
Correct Answer: A
Marking Scheme: 1 Mark
Q7.
AgCl decomposes in sunlight:
2AgCl → 2Ag + Cl2
Grey colour appears due to silver metal.
Assertion = True
Reason = True and explains assertion.
Correct Answer: A
Marking Scheme: 1 Mark
SECTION B – VERY SHORT ANSWER QUESTIONS
[4 × 2 = 8 Marks]
Q8. Balanced Chemical Equations [2]
(i) Respiration
C6H12O6 (aq) + 6O2 (g) → 6CO2 (g) + 6H2O (l) + Energy
(ii) Rusting of Iron
4Fe (s) + 3O2 (g) + xH2O (l) → 2Fe2O3·xH2O (s)
(Rust)
Marking Scheme:
- First equation = 1 Mark
- Second equation = 1 Mark
Q9. Differentiate between Breathing and Cellular Respiration [2]
| Breathing | Cellular Respiration |
|---|---|
| Physical process of inhalation and exhalation | Biochemical breakdown of food |
| Occurs in lungs | Occurs inside cells (mitochondria) |
| No energy released | Energy released in form of ATP |
Marking Scheme:
- Any two correct differences = 2 Marks
Q10. Identify X and Y [2]
Brown shiny metal:
X = Copper (Cu)
Black compound:
Y = Copper Oxide (CuO)
Equations:
2Cu + O2 → 2CuO
CuO + H2 → Cu + H2O
Marking Scheme:
- Identification = 1 Mark
- Equations = 1 Mark
Q11. Functions of Digestive Secretions [2]
(i) Hydrochloric Acid (HCl)
Location: Stomach
Functions:
- Makes medium acidic
- Activates pepsin enzyme
- Kills germs
(ii) Bile Juice
Location: Small intestine (duodenum)
Functions:
- Emulsifies fats
- Neutralizes acidic food from stomach
Marking Scheme:
- HCl = 1 Mark
- Bile juice = 1 Mark
SECTION C – SHORT ANSWER QUESTIONS
[2 × 3 = 6 Marks]
Q12. Experiment: CO2 Released During Respiration [3]
Experiment Setup:
Take germinating seeds in a conical flask.
Close flask with cork fitted with delivery tube.
Dip delivery tube into test tube containing lime water.
Observation:
Lime water turns milky due to CO2.
Reaction:
CO2 + Ca(OH)2 → CaCO3 + H2O
If connected to water setup, water level rises because oxygen is used and CO2 absorbed.
Precautions:
- Use germinating seeds only.
- Apparatus must be airtight.
- Fresh lime water should be used.
Marking Scheme:
- Setup = 1 Mark
- Observation = 1 Mark
- Precautions = 1 Mark
Q13. Write Equations and Reaction Type [3]
(i) Iron + Copper Sulphate
Fe + CuSO4 → FeSO4 + Cu
Type:
Displacement Reaction
(ii) Barium Chloride + Sodium Sulphate
BaCl2 + Na2SO4 → BaSO4↓ + 2NaCl
Type:
Double Displacement (Precipitation) Reaction
(iii) Slaked Lime Reaction
Ca(OH)2 + CO2 → CaCO3 + H2O
Type:
Combination Reaction
Marking Scheme:
- Each equation + type = 1 Mark
SECTION D – LONG ANSWER QUESTION
[1 × 5 = 5 Marks]
Q14.
(a) Pathway of Air in Human Respiratory System [2]
Path:
Nostrils → Nasal Cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
(Labelled diagram to be drawn showing:)
- Trachea
- Bronchi
- Alveoli
Marking Scheme:
- Correct diagram = 1 Mark
- Proper labeling = 1 Mark
(b) Adaptations of Alveoli [2]
- Large surface area due to millions of alveoli.
- Thin walls for rapid diffusion.
- Rich blood supply through capillaries.
- Moist surface helps gas diffusion.
Marking Scheme:
- Any four points = 2 Marks
(c) Need of Respiratory Pigment [1]
Simple diffusion is too slow in large organisms.
Hence oxygen transport needs a pigment.
Respiratory pigment = Haemoglobin
Marking Scheme:
- Correct reason + pigment = 1 Mark
SECTION E – CASE STUDY QUESTION
[1 × 4 = 4 Marks]
Q15.
(a) Thermite Reaction Equation [1]
Fe2O3 + 2Al → Al2O3 + 2Fe + Heat
Marking Scheme:
Correct balanced equation = 1 Mark
(b) Oxidized species and Oxidizing agent [1]
Oxidized species: Aluminium (Al)
Oxidizing agent: Iron(III) oxide (Fe2O3)
Marking Scheme:
Correct identification = 1 Mark
(c) Respiration vs Thermite Reaction [2]
In thermite reaction or combustion, energy is released rapidly as heat and light.
In respiration, glucose breaks down in a slow, controlled manner using enzymes.
Energy is released in small amounts and stored as ATP (Adenosine Triphosphate) for cellular activities.
Marking Scheme:
- Difference explained = 1 Mark
- Role of ATP = 1 Mark
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