Proteins make up many many important structures in our cells ( ex : receptors , Enzymes , integral proteins and so on )
Complete Question
The complete question is shown on the first uploaded image
Answer:
The concentration of
that should used originally is 
Explanation:
From the question we are told that
The necessary elementary step is

The time taken for sixth of 0.5 M of reactant to react 
The time available is 
The desired concentration to remain
Let Z be the reactant , Y be the first product and X the second product
Generally the elementary rate law is mathematically as

Where k is the rate constant ,
is the concentration of Z
From the elementary rate law we see that the reaction is second order (This because the concentration of the reactant is raised to power 2 )
For second order reaction

Where
is the initial concentration of Z which a value of 
From the question we are told that it take 9 hours for the concentration of the reactant to become


So


=> 
For 





I think its 2-, it gained 2 electrons.
When the moles of CH3COOH = volume of CH3COOH * no.of moles of CH3COOH
moles of CH3COOH = 35ml * 0.15 m/1000 =0.00525 mol
moles of NaOH = volume of NaOH*no.of moles of NaOH
= 17.5 ml * 0.15/1000 = 0.002625
SO the reaction after add the NaOH:
CH3COOH(aq) +OH- (aq) ↔ CH3COO-(aq) +H2O(l)
initial 0.00525 0 0
change - 0.002625 +0.002625 +0.002625
equilibrium 0.002625 0.002625 0.002625
When the total volume = 35ml _ 17.5ml = 52.5ml = 0.0525L
∴[CH3COOH] = 0.002625/0.0525 = 0.05m
and [CH3COO-]= 0.002625/0.0525= 0.05 m
when PKa = -㏒Ka
= -㏒1.8x10^-5 = 4.74
by substitution in the following formula:
PH = Pka + ㏒[CH3COO-]/[CH3COOH]
= 4.74 + ㏒(0.05/0.05) = 4.74
∴PH = 4.74