Answer:
Cyanobacteria, Azotobactor and Azospirillum are the microbes which is required for nitrogen cycle.
Explanation:
Nitrogen Cycle is a type of cycle in which nitrogen moves from atmosphere to the earth surface and again return back to the atmosphere. Cyanobacteria, Azotobactor and Azospirillum are the microbes which is required for nitrogen cycle. If these microbes is vanished from the environment, the nitrogen cannot be converted into other forms. Carbon is present in the atmosphere in carbondioxide form. This CO2 is used by the plants from atmosphere and make food from it. When these plants are eaten by animals, this CO2 is again release in the atmosphere. Due to global warming, the microbes present in the soil die due to increase in temperature of the soil. Levels of CO2 and CH4 increases if the soil warms up. With the increase in temperature, soil respiration increases which leads to more emission of CO2 and as a result more global warming occurs.
Answer:- 9.4 minutes.
Solution:- Radioactive decay obeys first order reaction kinetics and the equation used to solve this type of problems is:

where, k is decay constant and t is the time.
is the initial amount of the radioactive substance and N is the remaining amount.
Since the value of decay constant is not given, so we need to calculate it first from given half life by using the formula:

where
stands for half life.
Given half life is 3.0 minutes.
So, 

Let's plug in the values in the first order reaction equation and solve it for t.

It could also be written as:



k = 9.4 min
So, the radioactive substance would take 9.4 minutes to decay from 40.0 grams to 4.5 grams.
<span>choices are:
Zirconium metal plus hydrogen chloride yields zirconium chloride solution and hydrogen gas
Xenon solid plus hydrochloric acid yields xenon chloride and hydrogen gas
Zinc metal plus hydrogen chloride yields zinc dichloride plus hydrogen gas
Zinc metal plus an aqueous solution of hydrochloric acid yields an aqueous solution of zinc chloride plus hydrogen gas
right ans is:
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Zinc metal plus an aqueous solution of hydrochloric acid yields an aqueous solution of zinc chloride plus hydrogen gas<span>
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