An indicator that remains colorless in acid and turns pink in base is:
A. Litmus
B. Turmeric
C. Methyl orange
D. Phenolphthalein
Answer: Option D
Solution (By JKSSB Mock Tests)
Phenolphthalein: pH range 8.3–10; colorless below 8.3, pink above. Litmus is red in acid, blue in base. Methyl orange red in acid, yellow in base. Turmeric yellow in acid, reddish-brown in base.
Explanation:
Hydrogen has a very high calorific value of about 141.9 kJ/g (higher heating value) or ~150 kJ/g approximate. This makes it an excellent fuel, though storage is challenging. Methane ~55 kJ/g, petrol ~47 kJ/g. Hydrogen fuel cells use it efficiently.
Explanation:
In the liver, methanol is oxidized to formaldehyde, then to formic acid, which damages the optic nerve and can cause blindness or death. Ethanol is used as an antidote by competing for the enzyme alcohol dehydrogenase.
Explanation:
Azotobacter is a free-living aerobic bacterium that fixes atmospheric nitrogen in the soil, making it available to non-leguminous crops. Rhizobium is symbiotic and specific to legumes. Nitrobacter and Nitrosomonas are involved in nitrification (converting ammonia to nitrites/nitrates), not nitrogen fixation.
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