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Q1. The chemical name of lime water is:
Lime water is a dilute solution of calcium hydroxide [Ca(OH)₂] in water. It is prepared by dissolving slaked lime (calcium hydroxide) in water. Calcium chloride is a different compound, calcium carbonate is limestone/marble, and calcium oxide is quick lime. So calcium hydroxide is correct.
Q2. All metal carbonates react with acids to give:
When a metal carbonate reacts with an acid, the products are a salt, carbon dioxide gas, and water. For example: Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O. Oxygen, hydrogen, and bases are not produced in this reaction. So salt, carbon dioxide and water is correct.
Q3. Lime water test is used to detect:
Lime water (calcium hydroxide solution) is used to test for the presence of carbon dioxide gas. When CO₂ is passed through lime water, it turns milky due to the formation of calcium carbonate (CaCO₃). Nitrogen, hydrogen, and oxygen do not react with lime water in this way. So carbon dioxide is correct.
Q4. The colour of solution formed when CuO reacts with HCl is:
Copper oxide (CuO) is a black solid. When it reacts with hydrochloric acid (HCl), it forms copper chloride (CuCl₂) and water. The copper chloride solution has a blue-green colour. So the solution formed is blue-green.
Q5. On passing excess CO₂ through lime water, the solution becomes:
When CO₂ is passed through lime water, it first turns milky due to the formation of CaCO₃. On passing excess CO₂, the milky solution becomes clear (colourless) again because CaCO₃ dissolves to form soluble calcium bicarbonate [Ca(HCO₃)₂]. So colourless is correct.
Q6. Which of the following reactions produces CO₂?
Metal carbonates react with acids to produce salt, carbon dioxide, and water. For example: CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O. Base + acid gives salt and water (no CO₂). Metal oxide + acid gives salt and water (no CO₂). Acid + metal gives salt and hydrogen (no CO₂). So metal carbonate + acid is correct.
Q7. NaOH reacts with HCl to form:
Sodium hydroxide (NaOH) reacts with hydrochloric acid (HCl) in a neutralisation reaction to form sodium chloride (NaCl) and water (H₂O). The reaction is: NaOH + HCl → NaCl + H₂O. So NaCl is correct.
Q8. The general reaction of metallic oxide with acid is:
Metallic oxides are basic in nature. When a metallic oxide reacts with an acid, it forms a salt and water. For example: CuO + 2HCl → CuCl₂ + H₂O. Hydrogen gas is not produced. So salt + water is correct.
Q9. The reaction of a metal with an acid generally produces:
When a metal reacts with an acid, it produces a salt and hydrogen gas. For example: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Oxygen is not produced, and base and water are from neutralisation. So salt and hydrogen is correct.
Q10. Sodium hydrogen carbonate reacts with acid to produce:
Sodium hydrogen carbonate (NaHCO₃) reacts with acid to produce a salt, carbon dioxide, and water. For example: NaHCO₃ + HCl → NaCl + CO₂ + H₂O. This is why baking soda is used to neutralise acid in the stomach — it releases CO₂. So salt, carbon dioxide and water is correct.
Q11. Which metal is most commonly used in the laboratory to study the reaction between metals and dilute acids?
Zinc is commonly used in the laboratory to study the reaction between metals and dilute acids because it reacts readily with dilute acids (like HCl and H₂SO₄) to produce hydrogen gas. Gold and platinum are noble metals and do not react with dilute acids. Copper reacts only with concentrated acids. So zinc is correct.
Q12. The general reaction of acid with metal is:
The general reaction of an acid with a metal is: Acid + Metal → Salt + Hydrogen gas. For example: 2HCl + Zn → ZnCl₂ + H₂↑. Oxide + water is not formed, base + water is neutralisation, and salt only is incomplete. So salt + hydrogen is correct.
Q13. Which gas is evolved in most reactions of acids with metals?
In most reactions of acids with metals, hydrogen gas is evolved. For example: Mg + 2HCl → MgCl₂ + H₂↑. Oxygen is not evolved, nitrogen is not involved, and CO₂ is from carbonates, not metals. So hydrogen is correct.
Q14. Baking soda reacts with acid in stomach producing:
Baking soda (sodium hydrogen carbonate, NaHCO₃) is an antacid. When it reacts with excess stomach acid (HCl), it produces carbon dioxide gas (CO₂), salt, and water. The CO₂ causes burping, which provides relief. So carbon dioxide is correct.
Q15. Which substance shows no colour change in neutral solution with phenolphthalein?
Phenolphthalein is colourless in acidic and neutral solutions. It turns pink only in basic solutions. So an acid shows no colour change with phenolphthalein (it remains colourless). Base would turn pink, salt and water are neutral (also colourless), but the question asks which substance shows no colour change — acid is the most direct answer.
Q16. Metals displace hydrogen from:
Active metals displace hydrogen from acids to form salts and hydrogen gas. For example: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Some metals displace hydrogen from water (e.g., sodium), but not all metals do. Metals do not displace hydrogen from salts (they displace other metals). So acids is correct.
Q17. Which acid is commonly used to study the reaction between acids and metal carbonates in the laboratory?
Hydrochloric acid (HCl) is commonly used in the laboratory to study the reaction between acids and metal carbonates because it reacts readily and the products (salt, CO₂, water) are easy to identify. Dilute sulphuric acid can also be used, but HCl is more common for this activity. So hydrochloric acid is correct.
Q18. Copper oxide dissolves in acid because it is:
Copper oxide (CuO) is a basic oxide. It reacts with acids to form salt and water: CuO + 2HCl → CuCl₂ + H₂O. It dissolves in acid because it is basic in nature. It is not neutral, acidic, or amphoteric (ZnO and Al₂O₃ are amphoteric). So basic oxide is correct.
Q19. Sodium carbonate reacts with dilute HCl to produce:
Sodium carbonate (Na₂CO₃) reacts with dilute hydrochloric acid to form sodium chloride (NaCl), carbon dioxide (CO₂), and water (H₂O). The reaction is: Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O. So NaCl, CO₂ and H₂O is correct.
Q20. Carbon dioxide gas turns lime water milky due to formation of:
Carbon dioxide reacts with lime water [Ca(OH)₂] to form calcium carbonate (CaCO₃), which is insoluble and makes the solution milky. The reaction is: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. CaCl₂, CaSO₄, and CaO are not formed in this reaction. So CaCO₃ is correct.
Q21. The products of neutralisation reaction are:
A neutralisation reaction is the reaction between an acid and a base. The products are always a salt and water. For example: NaOH + HCl → NaCl + H₂O. Acid and base are reactants, not products. Salt and hydrogen is from acid + metal. So salt and water is correct.
Q22. The reaction of acid with base always produces:
The reaction between an acid and a base is called neutralisation. It always produces a salt and water. For example: KOH + HNO₃ → KNO₃ + H₂O. Metal oxide is not formed, hydrogen gas is from acid + metal, and CO₂ is from carbonate + acid. So salt and water is correct.
Q23. Which of the following is a basic oxide?
Copper oxide (CuO) is a basic oxide — it reacts with acids to form salt and water. NO₂, SO₂, and CO₂ are acidic oxides — they react with bases to form salt and water. So CuO is correct.
Q24. The gas evolved when a metal reacts with an acid burns with a:
Hydrogen gas is evolved when a metal reacts with an acid. Hydrogen is identified by the “pop sound” it makes when a burning splint is brought near it. A blue flame is from burning hydrogen, but the characteristic test is the pop sound. So pop sound is correct.
Q25. When zinc granules react with dilute sulphuric acid, bubbles are seen because of the evolution of:
Zinc granules react with dilute sulphuric acid to produce zinc sulphate and hydrogen gas. The bubbles seen are hydrogen gas: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Oxygen, nitrogen, and CO₂ are not produced. So hydrogen gas is correct.
Q26. Phenolphthalein is colourless in:
Phenolphthalein is a synthetic indicator that remains colourless in acidic solutions. It turns pink in basic solutions. In neutral solutions, it is also colourless, but the standard test is that it is colourless in acid. So acidic solution is correct.
Q27. When acid is added to a pink phenolphthalein solution, the colour:
Phenolphthalein turns pink in basic solutions. When an acid is added to this pink solution, the base is neutralised and the solution becomes neutral or acidic. As a result, the pink colour disappears (becomes colourless). So disappears is correct.
Q28. In a neutralisation experiment, phenolphthalein turns pink when added to:
Phenolphthalein is colourless in acidic and neutral solutions but turns pink in basic solutions. In a neutralisation experiment, it is used to detect the end point when the base is neutralised by acid. So base is correct.
Q29. Soap solution is used to test hydrogen gas because:
Soap solution is used to collect hydrogen gas in the form of bubbles. The hydrogen gas bubbles pass through the soap solution and form soap bubbles that rise up because hydrogen is lighter than air. The bubbles indicate the evolution of hydrogen gas. So it forms bubbles is correct.
Q30. The pink colour reappears when:
In a neutralisation experiment, phenolphthalein turns pink in basic solution. When acid is added, the pink colour disappears (neutralisation). If base is added again to the colourless solution, the pink colour reappears. So base is added again is correct.
Q31. The white precipitate formed in lime water is:
When CO₂ is passed through lime water, it forms a white precipitate of calcium carbonate (CaCO₃): Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O. Calcium hydroxide is the lime water itself, calcium oxide is quick lime, calcium chloride is a salt. So calcium carbonate is correct.
Q32. Hydrogen gas is collected in soap bubbles because:
Hydrogen gas is the lightest gas. It is collected in soap bubbles that rise up because the hydrogen-filled bubbles are lighter than air. It does not dissolve in soap solution or react with soap. So it is lighter than air is correct.
Q33. Zinc reacts with sodium hydroxide to produce:
Zinc reacts with sodium hydroxide (NaOH) to form sodium zincate (Na₂ZnO₂) and hydrogen gas. The reaction is: Zn + 2NaOH → Na₂ZnO₂ + H₂↑. Zinc hydroxide is formed when zinc reacts with water, zinc chloride is from HCl, zinc sulphate from H₂SO₄. So sodium zincate is correct.
Q34. Carbon dioxide turns lime water:
Carbon dioxide turns lime water milky due to the formation of insoluble calcium carbonate: Ca(OH)₂ + CO₂ → CaCO₃↓ + H₂O. It does not turn blue, colourless (that happens with excess CO₂), or yellow. So milky is correct.
Q35. Limestone, chalk and marble are forms of:
Limestone, chalk, and marble are all naturally occurring forms of calcium carbonate (CaCO₃). They have the same chemical composition but different physical properties. Calcium hydroxide is slaked lime, calcium oxide is quick lime, calcium chloride is a salt. So calcium carbonate is correct.
Q36. The compound Ca(HCO₃)₂ is:
Calcium bicarbonate [Ca(HCO₃)₂] is soluble in water. It is formed when excess CO₂ is passed through lime water, dissolving the insoluble CaCO₃. It is not a basic salt (it is a normal salt), not a precipitate (it is in solution), and not insoluble (it is soluble). So soluble in water is correct.
Q37. Hydrogen gas is identified by:
Hydrogen gas is identified by the characteristic “pop” sound it produces when a burning splint is brought near it. The hydrogen reacts with oxygen in the air to produce water, releasing energy as a pop. Precipitate formation, colour change, and smell are not tests for hydrogen. So pop sound is correct.
Q38. Zinc reacts with dilute sulphuric acid to form:
Zinc reacts with dilute sulphuric acid (H₂SO₄) to form zinc sulphate (ZnSO₄) and hydrogen gas: Zn + H₂SO₄ → ZnSO₄ + H₂↑. Zinc oxide is from reaction with oxygen, zinc chloride from HCl, zinc nitrate from HNO₃. So zinc sulphate is correct.
Q39. The gas evolved when metal carbonates react with acids is:
When metal carbonates react with acids, carbon dioxide gas is evolved. For example: Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O. Oxygen, hydrogen, and nitrogen are not produced in this reaction. So carbon dioxide is correct.
Q40. The gas produced when zinc reacts with sodium hydroxide is:
Zinc reacts with sodium hydroxide (NaOH) to produce sodium zincate and hydrogen gas: Zn + 2NaOH → Na₂ZnO₂ + H₂↑. This is an example of a metal reacting with a base. So hydrogen is correct.
Q41. Copper oxide reacts with hydrochloric acid to form:
Copper oxide (CuO) reacts with hydrochloric acid (HCl) to form copper chloride (CuCl₂) and water: CuO + 2HCl → CuCl₂ + H₂O. Copper sulphate would be from H₂SO₄, copper hydroxide from water/NaOH, copper nitrate from HNO₃. So copper chloride is correct.
Q42. The salt formed in NaOH + HCl reaction is:
Sodium hydroxide (NaOH) reacts with hydrochloric acid (HCl) to form sodium chloride (NaCl) and water: NaOH + HCl → NaCl + H₂O. Na₂O is sodium oxide, NaOH is the reactant, Na₂CO₃ is sodium carbonate. So NaCl is correct.
Q43. Neutralisation reaction is useful in treating:
Neutralisation is used to treat acidity (excess acid in the stomach). Antacids like milk of magnesia (a base) neutralise the excess stomach acid. Fever, fracture, and infection are treated differently. So acidity is correct.
Q44. Metallic oxides are generally:
Metallic oxides are generally basic in nature because they react with acids to form salt and water. For example: CuO + 2HCl → CuCl₂ + H₂O. They are not neutral (some are amphoteric), not gaseous (they are solids), and not acidic (non-metallic oxides are acidic). So basic is correct.
Q45. Lime water becomes clear again on passing excess CO₂ because:
When excess CO₂ is passed through lime water, the milky precipitate of CaCO₃ dissolves to form soluble calcium bicarbonate [Ca(HCO₃)₂]. This makes the solution clear again. The reaction is: CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂ (soluble). So CaCO₃ dissolves is correct.
Q46. Which reaction does NOT produce hydrogen gas?
In a neutralisation reaction (base + acid), the products are salt and water — no hydrogen gas is produced. Metal + water produces hydrogen (for active metals like Na, K), metal + base produces hydrogen (Zn + NaOH), and metal + acid produces hydrogen. So base + acid does NOT produce hydrogen gas.
Q47. Reaction of metals with bases is:
Only some metals (like zinc, aluminium, lead, tin) react with bases to produce hydrogen gas and salts. Most metals do not react with bases. Noble metals like gold and platinum do not react. So possible with some metals only is correct.
Q48. The reaction between an acid and a base to form salt and water is called:
The reaction between an acid and a base to form salt and water is called neutralisation. Displacement is one element replacing another, reduction is gain of electrons, oxidation is loss of electrons. So neutralisation is correct.
Q49. Sodium zincate is formed when zinc reacts with:
Sodium zincate (Na₂ZnO₂) is formed when zinc reacts with sodium hydroxide (NaOH): Zn + 2NaOH → Na₂ZnO₂ + H₂↑. HCl gives zinc chloride, H₂SO₄ gives zinc sulphate, HNO₃ gives zinc nitrate. So NaOH is correct.