| 21. | Phosphorus vapour comprises of |
| a. | P |
| b. | P₂ |
| c. | P₃ |
| d. | P₄ |
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Answer: (d).P₄
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| 22. | Conversion of yellow phosphorous to red phosphorous is done by heating it in covered retorts at __________ °C in absence of air. |
| a. | 50-80 |
| b. | 250-400 |
| c. | 1000-1200 |
| d. | 800-900 |
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Answer: (b).250-400
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| 23. | Commercial fertilisers are available mostly in the form of |
| a. | powder |
| b. | grannules |
| c. | lumps |
| d. | flakes |
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Answer: (b).grannules
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| 24. | Pick out the wrong statement. |
| a. | All the nitrogenous fertilisers are not soluble in water. |
| b. | A straight fertiliser contains only one nutrient. |
| c. | Calcium cynamide is used as weed killer in onion fields. |
| d. | The phosphorous nutrient makes the plant stem stronger and increases its branches. |
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Answer: (a).All the nitrogenous fertilisers are not soluble in water.
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| 25. | Ammonia synthesis gas is produced from natural gas by |
| a. | thermal cracking |
| b. | steam reforming |
| c. | partial oxidation |
| d. | hydrogenation |
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Answer: (b).steam reforming
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