I was going to say third quarter but since its not an answer maybe First quarter?
In the nucleus of each cell, The DNA molecule is packaged in to thread like structures called chromosomes.
Calculation: Molar mass of water = 180 % of water = > 180/286*100 = > 62.93%.
Answer: the percent by mass of water in the hydrate Na2CO3.10H20 is 62.93%.
I believe its
a)224000
b)0.000000015
c)0.655
d)9000
Moles of oxygen = mass/molar mass of O2 = 8/31.998 = 0.25 moles.
Number of particles = moles x 6.02 x 10^23 = 0.25 x 6.02 x 10^23 = 1.505 x 10^23 particles.
Hope this helps!