Given the mass of
=25.6 g
The molar mass of
=390.35g/mol
Converting mass of
to moles:

Converting mol
to mol S:

Converting mol S to atoms of S using Avogadro's number:
1 mol = 

Answer:
See detailed mechanism in the image attached
Explanation:
The mechanism shown in detail below is the synthesis of serine in steps.
The first step is the attack of the ethoxide ion base on the diethyl acetamidomalonate substrate giving the enolate and formaldehyde.
The second step is the protonation of the oxyanion from (1) above to form an alcohol as shown.
Acid hydrolysis of the alcohol formed in (3) above yields a tetrahedral intermediate, a dicarboxyamino alcohol.
Decarboxylation of this dicarboxyamino alcohol yields serine, the final product as shown in the image attached.
Probably b because soil can’t be the exact same and so that cancels out a and d
Solubility and temperatures are directly related. The higher the temperature of the solvent, the higher the solubility of the solute in the solvent.
Dissolving a solute in a solvent is an endothermic process hence providing heat favors the process. Higher temperatures cause the molecules of the solvent to have high kinetic energy hence bombard each other and with that of the solute with high frequency. This then ensures fast diffusion of the solute particles in the solvent.
t1/2 = ln 2 / λ = 0.693 / λ
Where t1/2 is the half life of the element and λ is decay constant.
32 = 0.693 / λ
λ = 0.693 / 32 (1)
Nt = Nο eΛ(-λt) (2)
Where Nt is atoms at t time, λ is decay constant and t is the time taken.
t = 1.9 hours = 1.9 x 60 min
From (1) and (2),
Nt = Nο e⁻Λ(0.693/32)*1.9*60
Nt = 0.085Nο
Percentage = (Nt/Nο) x 100%
= (0.085Nο/Nο) x 100%
= 8.5%
Hence, Percentage of remaining atoms with the original sample is 8.5%