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Q78 (CDS-I/2005) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Periodic table elements Answer Verified

Consider the following statements 1. Red phosphorus is poisonous whereas white phosphorus is non-poisonous. 2. Red phosphorus has low ignition temperature as compared to white phosphorus. Which of the statements given above is/are correct ?

Result
Your answer: —  Â·  Correct: D
Explanation

Statement 1 is incorrect because white phosphorus is highly toxic and poisonous, whereas red phosphorus is considered non-toxic and relatively harmless [t2][t6]. White phosphorus is so reactive that it must be stored under water to prevent spontaneous combustion in air [c1][t8]. Statement 2 is also incorrect because white phosphorus has a much lower ignition temperature (approximately 30°C to 35°C) compared to red phosphorus (approximately 240°C to 260°C) [t2][t3][t6]. White phosphorus spontaneously ignites at room temperature due to its strained tetrahedral P4 structure, while red phosphorus is a more stable polymeric form that requires significant heating to ignite [t2][t4][t5]. Therefore, red phosphorus has a higher ignition temperature than white phosphorus, making both statements false.

Sources

  1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 4: The World of Metals and Non-metals > Activity 4.8: Let us explore > p. 53
  2. [2] https://www.sciencedirect.com/topics/medicine-and-dentistry/phosphorus
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