RRB JE Chemistry Questions with Detailed Solutions

Get RRB JE Chemistry Questions to prepare for your upcoming exam. Solve the most expected questions and detailed solutions that can be asked in the exam.

Important RRB JE Chemistry Questions

Q1.
A student adds lead (II) nitrate (Pb(NO3)2) to an unknown solution. A yellow precipitate forms. What could the unknown solution be?
  • A.Potassium iodide (KI)
    ✓ Correct
  • B.Copper sulphate (CuSO4)
  • C.Sodium chloride (NaCl)
  • D.Barium sulphate (BaSO4)

Answer & Solution

Correct option is A

The correct answer is (A) Potassium iodide (KI)

Explanation:
• When a solution of Lead (II) nitrate is mixed with a solution of Potassium iodide, a classic double displacement reaction takes place.
• The lead ions (Pb²⁺) combine with the iodide ions (I⁻) to form Lead (II) iodide (PbI₂).
• Lead (II) iodide is highly insoluble in cold water and immediately precipitates out of the mixture as a brilliant, distinct yellow solid.
• The chemical equation is: Pb(NO₃)₂ (aq) + 2KI (aq) → PbI₂ (s) + 2KNO₃ (aq).

Information Booster:
• Double Displacement Reactions: These reactions occur when parts of two ionic compounds are exchanged, making two new compounds. A precipitation reaction is a common type of double displacement.
• Golden Rain Experiment: This specific reaction is famously known as the "Golden Rain" experiment. If the mixture is heated, the yellow precipitate dissolves, and upon cooling, it crystallizes into beautiful, shimmering golden flakes.

Additional Knowledge:
• Option B (Copper sulphate): Adding lead nitrate to copper sulphate would form lead sulphate (PbSO₄), which is a white precipitate, not yellow.
• Option C (Sodium chloride): This would form lead chloride (PbCl₂), which is also a white precipitate.
• Option D (Barium sulphate): Barium sulphate is already a highly insoluble white solid; it would not engage in an aqueous double displacement to yield a yellow color.
Q2.
Consider the reaction: CH3CH2OH+ Alkaline KMnO4→ Heat CH3COOH Which of the following statements is/are correct? (A) The reaction represents the oxidation of a primary alcohol to a carboxylic acid. (B) Alkaline KMnO4 acts as an oxidising agent. (C) Alkaline KMnO4 acts as a reducing agent.
  • A.Only B
  • B.A, B and C
  • C.Only A and C
  • D.Only A and B
    ✓ Correct

Answer & Solution

Correct option is D

The correct answer is (D) Only A and B

Explanation:
• The chemical equation shows the conversion of Ethanol (CH₃CH₂OH), which is a primary alcohol, into Ethanoic Acid (CH₃COOH), which is a carboxylic acid.
• Statement A is correct: This process adds oxygen and removes hydrogen from the ethanol molecule, making it a classic oxidation reaction.
• Statement B is correct: Alkaline Potassium Permanganate (KMnO₄) provides the nascent oxygen needed for this reaction, driving the oxidation of ethanol. Therefore, it is a strong oxidising agent.
• Statement C is incorrect: Since it causes oxidation, it cannot be a reducing agent. (In the process, the permanganate itself is reduced, but its role is as an oxidising agent).

Information Booster:
• Acidified Potassium Dichromate: Another widely used strong oxidising agent for converting primary alcohols directly to carboxylic acids is acidified Potassium Dichromate (K₂Cr₂O₇).
• Partial Oxidation: If a mild oxidising agent like PCC (Pyridinium chlorochromate) is used, the primary alcohol will stop at the aldehyde stage (Ethanal, CH₃CHO) instead of fully oxidizing to ethanoic acid.
• Identifying Primary Alcohols: In CH₃CH₂OH, the OH group is attached to a carbon atom that is bonded to only one other carbon, classifying it as primary.

Additional Knowledge:
• Option A (Only B): Ignores the fact that statement A is also completely accurate regarding the nature of the reactants and products.
• Option B and C: Both include Statement C, which is factually incorrect because KMnO₄ is an oxidising agent, not a reducing agent.
Q3.
Identify the CORRECT statement about the chlor-alkali process:
  • A.It is used for the preparation of Na2CO3 solution by electrolysis of brine.
  • B.Hydrogen gas is formed at the cathode and chlorine gas at the anode.
    ✓ Correct
  • C.Sodium hydroxide is generated near the anode during electrolysis.
  • D.NaOH is formed at the anode and chlorine gas at the cathode.

Answer & Solution

Correct option is B

The correct answer is (B) Hydrogen gas is formed at the cathode and chlorine gas at the anode.

Explanation:
• The chlor-alkali process is the industrial electrolysis of aqueous sodium chloride (brine).
• During the process, an electric current is passed through the brine solution. The chemical decomposition yields three critical products: Sodium Hydroxide (alkali), Chlorine gas, and Hydrogen gas.
• At the positive electrode (anode), chloride ions are oxidized to form chlorine gas (Cl₂). At the negative electrode (cathode), water is reduced to form hydrogen gas (H₂) and hydroxide ions.

Information Booster:
• Product Utility: Chlorine is heavily used in water treatment, PVC, and CFC manufacture. Hydrogen is used as fuel and for ammonia production for fertilizers. Sodium hydroxide is used for making soap, detergents, and paper.
• Formation of NaOH: Sodium ions (Na⁺) from the brine combine with hydroxide ions (OH⁻) generated at the cathode. Therefore, sodium hydroxide solution is formed *near the cathode*.
• Why is it called Chlor-Alkali? "Chlor" stands for the chlorine gas produced, and "alkali" stands for the sodium hydroxide produced, which is a strong base/alkali.

Additional Knowledge:
• Option A (Na2CO3 preparation): The Solvay process is used to prepare Sodium Carbonate (Na₂CO₃), not the chlor-alkali process.
• Option C (NaOH near anode): NaOH forms near the *cathode*, not the anode.
• Option D (NaOH at anode, Cl2 at cathode): This statement completely reverses the correct locations.
Q4.

Refer to the two statements given below and choose the CORRECT option. Statement A: While writing the chemical formula of a compound, the total positive and negative charges must balance each other. Statement B: Balancing valencies ensures that the compound formed is electrically neutral.

  • A.

    Statement A is incorrect but B is correct.

  • B.

    Both statements A and B are correct.

    ✓ Correct
  • C.

    Both statements A and B are incorrect.

  • D.

    Statement A is correct but B is incorrect.

Answer & Solution

Correct option is B

The correct answer is: B

Explanation:

  • Statement A is correct: The fundamental principle of writing a chemical formula for a stable ionic compound is that the total positive charge (from cations) must perfectly equal the total negative charge (from anions).
  • Statement B is correct: Valency represents the combining capacity of an element. By balancing these valencies (often using the criss-cross method), we ensure that the resulting molecule or formula unit has a net charge of zero, making the compound electrically neutral.

Information Booster:

  • The "criss-cross" method is the most common technique taught for writing chemical formulas. For example, to form Aluminum oxide, you take Aluminum (valency of +3) and Oxygen (valency of -2). Crossing their valencies as subscripts gives the neutral compound $\text{Al}_2\text{O}_3$.
  • Atoms combine to achieve the stable electron configuration of the nearest noble gas (an octet in their outermost shell).
  • Polyatomic ions (like SO42−\text{SO}_4^{2-}​ or NH4+\text{NH}_4^+​) act as a single unit with a net charge, and their overall charge must also be balanced when forming compounds.
Q5.
What happens to insoluble impurities during electrolytic refining?
  • A.They deposit on cathode
  • B.They dissolve completely
  • C.They settle as anode mud
    ✓ Correct
  • D.They evaporate

Answer & Solution

Correct option is C

The correct answer is (C) They settle as anode mud

Explanation:
• Electrolytic refining is widely used to obtain pure metals like copper, zinc, tin, silver, and gold from impure samples.
• In this setup, the thick block of impure metal acts as the anode (+), and a thin strip of pure metal acts as the cathode (-). The electrolyte is a salt solution of the metal.
• Upon passing electric current, pure metal dissolves from the anode into the electrolyte and then deposits on the cathode. The insoluble impurities fall to the bottom of the tank directly beneath the anode, forming a sludge known as "anode mud."r>
Information Booster:
• Soluble Impurities: Impurities that are more reactive than the metal being refined dissolve and remain in the electrolyte solution.
• Value of Anode Mud: In the refining of copper, the anode mud often contains valuable noble metals such as gold, silver, and platinum. Recovering these pays for the cost of the refining process!
• Electroplating: This utilizes the same principle, but the goal is to coat an object with a thin layer of a desired metal rather than refine a bulk block.

Additional Knowledge:
• Option A (Deposit on cathode): Only the pure ions of the target metal migrate to and deposit on the cathode.
• Option B (Dissolve completely): Only the *soluble* impurities go into the solution.
• Option D (Evaporate): Metals and solid impurities do not evaporate in a room-temperature aqueous electrolysis cell.
Q6.
Which pair of olfactory indicators loses its smell in a basic solution?
  • A.Vanilla essence and clove oil
    ✓ Correct
  • B.Onion and blue litmus
  • C.Turmeric and onion
  • D.Phenolphthalein and onion

Answer & Solution

Correct option is A

The correct answer is (A) Vanilla essence and clove oil

Explanation:
• Olfactory indicators are substances whose odor changes in acidic or basic media. They are especially useful for visually impaired students to detect acids and bases.
• Vanilla essence has a characteristic pleasant smell. In acidic solutions, the smell is retained, but in basic (alkaline) solutions, its smell vanishes entirely.
• Clove oil similarly retains its distinct odor in acidic environments but loses its characteristic smell when mixed with a base (like NaOH).

Information Booster:
• Onion Extract: Onion is another major olfactory indicator. Like vanilla and clove oil, onion paste or juice loses its pungent smell in a basic solution but retains it in an acidic solution.
• Visual Indicators: Most synthetic indicators are visual. For example, Phenolphthalein is colorless in acid and turns pink in a base. Methyl orange is red in acid and yellow in a base.
• Natural Indicators: Turmeric is a natural visual indicator. It stays yellow in acid but turns deep red in a basic medium.

Additional Knowledge:
• Option B (Blue litmus): Litmus is a visual indicator, not an olfactory one.
• Option C (Turmeric): Turmeric is a visual indicator, detecting bases by color change, not smell.
• Option D (Phenolphthalein): A synthetic visual indicator, offering no scent-based change.
Q7.
Which of the following is an advantage of paper cups over plastic cups?
  • A.They are stronger
  • B.They are biodegradable
    ✓ Correct
  • C.They are reusable
  • D.They are cheaper

Answer & Solution

Correct option is B

The correct answer is (B) They are biodegradable

Explanation:
• Paper is derived from wood pulp (plant material) and is an organic, biodegradable substance.
• Biodegradable means that natural microorganisms (bacteria and fungi) can easily break down the material into harmless, simpler substances (like water, carbon dioxide, and biomass) over a relatively short period.
• Plastic cups are synthetic polymers that are non-biodegradable, remaining in the environment for hundreds of years, causing severe pollution and choking wildlife. This makes paper a significantly more eco-friendly disposable option.

Information Booster:
• Kulhads (Clay Cups): An even better traditional alternative used in India is the 'kulhad'. It is completely biodegradable, enhances the taste, and provides employment to local potters without requiring deforestation.
• The Polyethylene lining issue: It is important to note that many modern commercial "paper" coffee cups have a thin plastic lining (polyethylene) inside to make them waterproof. This makes recycling them difficult, though they are still vastly superior to 100% plastic cups.
• Composting: True paper cups can be added to compost bins, returning nutrients to the soil.

Additional Knowledge:
• Option A (Stronger): Plastic cups are generally more structurally robust, waterproof, and tear-resistant than paper cups.
• Option C (Reusable): Disposable paper cups degrade quickly when wet and cannot be reused like thick hard plastics or ceramics.
• Option D (Cheaper): Plastic cups are often much cheaper to mass-produce than paper cups.
Q8.
Washing soda is commonly used to:
  • A.Remove grease and soften water
    ✓ Correct
  • B.Neutralise acids in human blood
  • C.Increase acidity in baked foods
  • D.Preserve meat for long periods

Answer & Solution

Correct option is A

The correct answer is (A) Remove grease and soften water

Explanation:
• Washing soda, chemically known as Sodium Carbonate Decahydrate (Na₂CO₃·10H₂O), is a highly basic salt.
• It acts as a powerful cleaning agent for domestic purposes like washing clothes, as it effectively reacts with and breaks down grease and oil.
• Its most vital industrial and domestic use is in the removal of permanent hardness of water. It precipitates calcium and magnesium ions (which cause hardness) as insoluble carbonates.

Information Booster:
• Manufacture: Washing soda is produced industrially using the Solvay process, which uses sodium chloride, ammonia, and carbon dioxide as raw materials.
• Other Uses: It is widely used in the glass, soap, and paper industries. It is also used in the manufacture of sodium compounds like borax.
• Baking Soda vs Washing Soda: Baking soda is Sodium Bicarbonate (NaHCO₃). Heating baking soda produces sodium carbonate, which upon recrystallization yields washing soda.

Additional Knowledge:
• Option B (Neutralise blood acids): Washing soda is highly corrosive and toxic to ingest; mild bases like baking soda (in antacids) are used for biological acidity, not washing soda.
• Option C (Baked foods): Baking soda is used for this, as it releases CO₂ gas upon heating, making the batter spongy. Washing soda is not used in food.
• Option D (Preserve meat): Common salt (Sodium Chloride, NaCl) is used for preserving meat, not washing soda.
Q9.
Which of the following best supports the concept that matter is made-up of particles?
  • A.A drop of ink spreads uniformly in water
    ✓ Correct
  • B.Water boils at 100°C
  • C.Ice melts to form water
  • D.Metals conduct electricity

Answer & Solution

Correct option is A

The correct answer is (A) A drop of ink spreads uniformly in water

Explanation:
• The spontaneous spreading of ink in water is a classic example of diffusion.
• Diffusion demonstrates that matter is composed of tiny, constantly moving particles that possess kinetic energy.
• As the ink particles and water particles collide and move randomly, they intermix on their own, filling the spaces between each other, which proves the particulate nature of matter.

Information Booster:
• Brownian Motion: The continuous zig-zag movement of colloidal particles in a dispersion medium, which also supports the kinetic theory of matter.
• Characteristics of Particles: Particles of matter have spaces between them, are continuously moving, and attract each other.
• Effect of Temperature: The rate of diffusion increases with an increase in temperature because the kinetic energy of the particles increases.

Additional Knowledge:
• Water boils at 100°C (Option B) & Ice melts to form water (Option C): These represent changes in the state of matter (boiling point and melting point) rather than direct visual evidence of the particulate nature in a mixed state.
• Metals conduct electricity (Option D): This indicates the presence of free electrons in metallic structures, demonstrating electrical properties rather than the general particulate nature of all matter.
Q10.
In a redox reaction, what is the role of a 'reducing agent'?
  • A.It is a catalyst that speeds up the reaction.
  • B.It is an agent that helps other substances to be oxidized.
  • C.It is a substance that causes reduction and itself gets oxidized.
    ✓ Correct
  • D.It is a substance that only participates in decomposition reactions.

Answer & Solution

Correct option is C

The correct answer is (C) It is a substance that causes reduction and itself gets oxidized.

Explanation:
• In a reduction-oxidation (redox) reaction, electron transfer is the fundamental mechanism.
• A reducing agent (or reductant) is a substance that donates electrons to another chemical species. By giving away electrons, it causes the other substance to be reduced.
• Concurrently, because the reducing agent has lost electrons in this process, it undergoes oxidation itself.

Information Booster:
• Oxidation vs. Reduction: Oxidation is the loss of electrons (or addition of oxygen/removal of hydrogen). Reduction is the gain of electrons (or removal of oxygen/addition of hydrogen).
• Oxidizing Agent: The exact opposite of a reducing agent. It accepts electrons, causing another substance to be oxidized, while it gets reduced itself.
• Classic Example: In the reaction CuO + H2 → Cu + H2O, Hydrogen (H2) acts as the reducing agent because it removes oxygen from Copper Oxide, becoming oxidized to water in the process.

Additional Knowledge:
• Option A (Catalyst): A catalyst changes reaction rates without being consumed or inherently transferring electrons as part of the core stoichiometry.
• Option B (Helps other substances to be oxidized): This is the definition of an oxidizing agent, not a reducing agent.
• Option D (Only in decomposition): Redox reactions occur across many types, including combination, displacement, and combustion; they are not limited to decomposition.
Q11.
Which of the following is an advantage of paper cups over plastic cups?
  • A.They are stronger
  • B.They are biodegradable
    ✓ Correct
  • C.They are reusable
  • D.They are cheaper

Answer & Solution

Correct option is B

The correct answer is (B) They are biodegradable

Explanation:
• The fundamental environmental advantage of paper cups over plastic cups is their biodegradability.
• Paper is made from cellulose (plant fiber), a natural material that can be broken down relatively quickly by microorganisms (bacteria and fungi) in the environment.
• Plastic cups, typically made from petroleum-based polymers (like polystyrene), are non-biodegradable. They accumulate in landfills and oceans, persisting for hundreds of years and causing severe ecological damage (such as microplastic pollution).

Information Booster:
• The Culhad Story: The Indian Railways experimented with "kulhads" (disposable clay cups) to replace plastic, which were highly eco-friendly but posed top-soil depletion issues. Paper cups became the balanced standard.
• Hidden Plastics: It should be noted that many commercial paper cups have a thin inner plastic lining (polyethylene) to prevent liquid from soaking through, which somewhat complicates their recycling process, though they still degrade vastly faster than solid plastic cups.

Additional Knowledge:
• Strength (Option A): Plastic cups are generally sturdier and less prone to collapsing when wet compared to plain paper.
• Reusable (Option C): Standard paper cups are designed for single use. Hard plastic cups are far more reusable.
• Cost (Option D): Historically, bulk thin plastic cups are often cheaper to manufacture than paper cups.
Q12.
Which element exists as a monoatomic molecule?
  • A.Oxygen
  • B.Chlorine
  • C.Nitrogen
  • D.Argon
    ✓ Correct

Answer & Solution

Correct option is D

The correct answer is (D) Argon

Explanation:
• Atomicity is defined as the number of atoms present in a single molecule of an element.
• Argon (Ar) is a noble gas belonging to Group 18 of the periodic table.
• Elements in this group have a completely filled outermost electron shell (an octet). Because they are already perfectly stable, they do not need to share, gain, or lose electrons by bonding with other atoms.
• Therefore, Argon exists independently in nature as a single atom, making its atomicity "1" (monoatomic).

Information Booster:
• Other Noble Gases: Helium (He), Neon (Ne), Krypton (Kr), Xenon (Xe), and Radon (Rn) are all monoatomic for the same reason.
• Metals: All solid metals (like Iron, Copper, Gold) are also generally considered to have an atomicity of 1 when written in chemical equations, though they exist as giant metallic lattices.

Additional Knowledge:
• Oxygen (Option A): Oxygen requires two electrons to complete its octet, so two atoms bond together, forming a diatomic molecule (O2). Ozone (O3) is triatomic.
• Chlorine (Option B): Chlorine forms diatomic molecules (Cl2) sharing one electron each to complete their shells.
• Nitrogen (Option C): Nitrogen forms a very strong diatomic molecule (N2) using a triple bond.
Q13.
What happens to insoluble impurities during electrolytic refining?
  • A.They deposit on cathode
  • B.They dissolve completely
  • C.They settle as anode mud
    ✓ Correct
  • D.They evaporate

Answer & Solution

Correct option is C

The correct answer is (C) They settle as anode mud

Explanation:
• Electrolytic refining is a widely used process for purifying metals, notably copper, zinc, and gold.
• In this process, a thick block of impure metal acts as the anode (positive electrode), while a thin strip of pure metal acts as the cathode (negative electrode).
• When current passes, the pure metal from the anode dissolves into the electrolyte and deposits onto the cathode.
• Soluble impurities go into the solution, whereas insoluble impurities (which are heavier and cannot dissolve) simply fall off the dissolving anode and accumulate at the bottom of the tank. This collection of impurities is called "anode mud" or "anode slime".

Information Booster:
• Economic Value: Anode mud is highly valuable. For instance, during the refining of copper, the anode mud often contains trace amounts of precious metals like silver, gold, and platinum, which are later recovered.
• Electrolyte: The solution used is typically a salt of the metal being refined. For copper, acidified copper sulphate (CuSO4) is used.

Additional Knowledge:
• Option A (Deposit on cathode): Only the pure metal ions are reduced and deposited on the cathode.
• Option B (Dissolve completely): Only the more reactive (soluble) impurities dissolve into the electrolyte.
• Option D (Evaporate): Metal impurities do not evaporate at room temperature within an aqueous electrolytic cell.
Q14.

Refer to the two statements given below and choose the CORRECT option. Statement A: While writing the chemical formula of a compound, the total positive and negative charges must balance each other. Statement B: Balancing valencies ensures that the compound formed is electrically neutral.

  • A.

    Statement A is incorrect but B is correct.

  • B.

    Both statements A and B are correct.

    ✓ Correct
  • C.

    Both statements A and B are incorrect.

  • D.

    Statement A is correct but B is incorrect.

Answer & Solution

Correct option is B

The correct answer is (B) Both statements A and B are correct.

Explanation:
• Statement A is correct: When writing the chemical formula for an ionic compound, the fundamental rule is that the total positive charge of the cations (metal ions) must exactly equal the total negative charge of the anions (non-metal ions). We use the "criss-cross" method of valencies to achieve this balance.
• Statement B is correct: The underlying chemical principle behind balancing valencies/charges is the necessity of electrical neutrality. A stable ionic compound in nature does not hold a net electrical charge; it must be completely neutral overall.
• Therefore, Statement B provides the logical reasoning for the rule stated in Statement A.

Information Booster:
• Example - Aluminium Oxide: Aluminium has a valency of +3 (Al³⁺), and Oxygen has a valency of -2 (O²⁻). To balance the charges, we need two Al ions (+6) and three O ions (-6), giving the formula Al2O3, which has a net charge of zero.
• Polyatomic Ions: This rule strictly applies to polyatomic ions as well. For Ammonium sulphate, NH4⁺ (+1) and SO4²⁻ (-2) combine in a 2:1 ratio to form (NH4)2SO4.

Additional Knowledge:
• Any option suggesting that one or both of these fundamental laws of chemical nomenclature are incorrect demonstrates a misunderstanding of basic stoichiometry.

Q15.
Washing soda is commonly used to:
  • A.Remove grease and soften water
    ✓ Correct
  • B.Neutralise acids in human blood
  • C.Increase acidity in baked foods
  • D.Preserve meat for long periods

Answer & Solution

Correct option is A

The correct answer is (A) Remove grease and soften water

Explanation:
• Washing soda (Sodium carbonate decahydrate, Na2CO3·10H2O) is a highly basic salt.
• In domestic settings, it is famously used as a cleansing agent to remove tough grease and stubborn stains from clothes.
• Crucially, it is used for the removal of permanent hardness of water. It reacts with the calcium and magnesium chlorides and sulphates (the cause of hard water) to form insoluble precipitates, making the water soft and allowing soap to lather easily.

Information Booster:
• Manufacturing: It is manufactured industrially via the Solvay Process, using sodium chloride, ammonia, and carbon dioxide.
• Other Uses: It is also a key raw material in the manufacture of glass, soap, and paper, and is used to synthesize sodium compounds like borax.

Additional Knowledge:
• Neutralise stomach acids (Option B): Baking soda (Sodium bicarbonate, NaHCO3) is used as a mild antacid, not washing soda, which is too caustic for ingestion.
• Baked foods (Option C): Baking soda or baking powder is used to make cakes spongy (by releasing CO2), not washing soda.
• Preserving meat (Option D): Common salt (Sodium chloride, NaCl) is traditionally used as a preservative, not washing soda.

More Important Questions