General Science Previous Year Questions (PYQ) with Answers – Page 4

Consider the following pairs of reactions and properties : Reaction — Property I. Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g) — Fe is reductant II. Zn(s) + CuSO₄(aq) → ZnSO₄(aq) + Cu(s) — Cu is being reduced III. Br₂(l) + 2I⁻(aq) → 2Br⁻(aq) + I₂(s) — Br₂ is reductant IV. CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) — C atom in CH₄ is oxidized Which of the above pairs are correct?

Coconut oil upon hydrolysis with potassium hydroxide gives :

Which one of the following statements about xylem vessels in plants is not correct?

Which one of the following effects best explains the high partial pressure of carbon dioxide causing haemoglobin to release oxygen in actively respiring tissues?

Which one of the following statements about arteries is not correct?

What are the approximate percentages by mass of nitrogen and hydrogen respectively in urea?

Consider the following pairs : Chemical Reaction — Type of Chemical Reaction I. Fe(s) + CuSO₄(aq.) → FeSO₄(aq.) + Cu(s) — Displacement reaction II. Na₂SO₄(aq.) + BaCl₂(aq.) → BaSO₄(s) + 2NaCl(aq.) — Double displacement reaction III. Fe₂O₃(s) + 3CO(g) → 2Fe(s) + 3CO₂(g) — Redox reaction IV. 2KClO₃(s) → 2KCl(s) + 3O₂(g) — Thermal decomposition reaction How many of the pairs given above are correctly matched?

Which of the following is/are the basic step(s) in genetically modifying an organism? 1. Identification of DNA with desirable genes 2. Introduction of the identified DNA into the host 3. Maintenance of introduced DNA in the host and transfer of the DNA to its progeny Select the correct answer using the code given below.

Consider the following statements : I. The leaves of nettle, a herbaceous plant, cause painful stings when touched accidentally because of the secretion of formic acid. II. When gypsum is heated at 100°C, it forms calcium carbonate hemihydrate, called Plaster of Paris. III. When moistened with water, anhydrous copper sulphate forms a green-coloured copper sulphate dihydrate. Which of the statements given above is/are correct?

Consider the following statements : I. A solution of iodine in ethanol known as 'tincture of iodine' is a heterogeneous mixture. II. A suspension is a heterogeneous mixture and its particles scatter a beam of light passing through it, making its path visible. III. A colloidal solution, although it appears homogeneous, is a heterogeneous mixture. Which of the statements given above are correct ?

Consider the following statements about genetic engineering:

1. The technique of genetic engineering involves creation of recombinant DNA, use of gene cloning and gene transfer.

2. Restriction enzymes cut DNA at specific locations.

3. Restriction enzymes split the entire double-stranded DNA into two strands.

Which of the statements given above is/are correct?

Which one of the following statements about natural selection is not correct?

Consider the following statements : I. Zinc metal, when treated with both HCl (aq.) and NaOH (aq.) separately, produces molecular hydrogen. II. An aqueous copper sulphate solution cannot be kept in a zinc vessel. III. Lemon, tamarind and tomato are natural sources of citric acid, oxalic acid and tartaric acid, respectively. Which of the statements given above are correct?

1.7 g of silver nitrate is dissolved in 100 g of water, and 0.585 g of sodium chloride is dissolved in 100 g of water. Both are mixed and a chemical reaction occurs. 1.435 g of silver chloride and 0.85 g of sodium nitrate are formed. Which law of chemical combination is shown by the above reaction?

In a dry test tube, 2 mL of HCl (0.1 N) is taken. To this, 4 mL of NaOH (0.1 N) is added. The solution is stirred well, followed by the addition of 2 drops of phenolphthalein. What will be the colour of the solution?

Superphosphate of lime—a phosphate fertilizer—is obtained by the reaction of

Consider the following statements regarding nitrogen : I. Nitrogen contains a triple bond. II. Nitrogen is a triatomic gas. III. Forces acting between nitrogen molecules are weak van der Waals forces. Which of the statements given above are correct?

Consider the following statement : "Acids are substances that dissociate in water to give hydrogen ions H⁺ (aq), and bases are substances that produce hydroxyl ions OH⁻ (aq)." The above statement is based on which one of the following concepts?

Consider the following statements regarding the properties of hydrogen and water : I. Tritium, the isotope of hydrogen, is radioactive and emits low energy alpha particles. II. In the gas phase, the structure of water is linear. III. The basic principle of a hydrogen economy is the transportation and storage of energy in the form of liquid or gaseous molecular hydrogen. Which of the statements given above is/are not correct?

Which of the following are oxidation reactions? I. Rusting of iron II. Burning of fuel III. Rancidity of oils and fats IV. Browning of fruits Select the correct answer using the code given below.