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BlueSky06
To find the mass of reagent to be added in the reaction, we need to determine the pH of the buffer. Using the following equation

pH= pKa + log ([NH3] / [NH4+])
     = 9.26 + LOG ( 0.3 / 0.3)
     = 9.26

[h+]= 5.5x10^-10 M, you need to increase that concentration for a ph of 8.6, [H+] needs to be 2.51x10^-9M

2.51x10^-9 moles - 5.5x10^10 moles = 1.96x10^-9 moles 

1.96x10^-9 x 36.45g/mole = 7.14x10^-8 g

So the mass of HCI that you should add to the reaction is 7.14x10^-8 g

The mass of the correct reagent to be added is; 5.228 g

The complete question is;

A 1.0-L buffer solution initially contains 0.30 mol of NH₃ and 0.30 mol of NH₄Cl. In order to adjust the buffer pH to 8.80, should you add NaOH or HCl to the buffer mixture? What mass of the correct reagent should you add?

Volume of buffer solution; V = 1.0 L

Number of moles of NH₃; n_a = 0.30 mol

Number of moles of NH₄Cl; n_b = 0.30 mol

Required pH of the buffer; PH_req = 8.80

Now, formula for molarity is;

M = number of moles/volume

Since NH₃ and NH₄Cl have the same number of moles, then molarity for both will be the same;

M = 0.3/1

M = 0.3 M

Using the Henderson Hasselbalch equation, we can evaluate the initial PH of the solution;

PH = pkₐ + log([A⁻]/[HA])

Where;

pkₐ is acid dissociation constant

A⁻ is concentration of conjugate base which in this case is for NH₃ = 0.3 M

HA is concentration of conjugate acid which in this case is for NH₄Cl =0.3 M

From tables, the pkₐ for NH₄Cl is 9.252. Thus;

PH_initial  = 9.252 + log(0.3/0.3)

PH_initial  = 9.252

From the question, the PH needs to be adjusted to 8.8. Thus it means the PH needs to be reduced. If we make an unknown concentration which it is reduced by to be x, then it means that;

New A⁻ = 0.3 - x

New HA = 0.3 + x

Thus;

8.8 = 9.252 +  log [(0.3 - x)/[0.3 + x)]

Rearranging gives;

8.8 - 9.252  = log [(0.3 - x)/[0.3 + x)]

-0.452 = log [(0.3 - x)/(0.3 + x)]

[tex]10^{-0.452}[/tex] = (0.3 - x)/(0.3 + x)

Solving this equation gives;

x = 0.1434 M

Thus, number of moles of hydronium ions = 0.1434 × 1

number of moles of hydronium ions = 0.1434 mol

Molar mass of HCl is  36.458 g/mol.

Thus;

mass of reagent to be added = 36.458 × 0.1434

mass of reagent to be added = 5.228 g

Read more at; https://brainly.com/question/13775917

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