The balanced equation between the 
and 
is:
Formula of molarity is:
Substituting the values,
So, number of moles of is 
.
From the balanced equation it is clear that for 1 mole of , 2 moles of are required.
Hence, 0.21 mole of = 
Molar mass of = 
So, the mass of = 
I think it will be B. Hope it helps :)
The more focused the rays are, the more energy an area receives, and the warmer it is. The lowest latitudes get the most energy from the Sun. The highest latitudes get the least. The difference in solar energy received at different latitudes drives atmospheric circulation.
Answer:
Helium is the second element on the periodic table. It is located in period 1 and group 18 or 8A on the righthand side of the table. This group contains the noble gases, which are the most chemically inert elements on the periodic table. Each He atom has two protons and usually two neutrons and two electrons.
Explanation:
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