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A sample of 7.70 l of nh3 (ammonia) gas at 22 ∘c and 735 torr is bubbled into a 0.250 l solution of 0.400 mol l−1 hcl (hydrochloric acid). the kb value for nh3 is 1.8×10−5. part a assuming all the nh3 dissolves and that the volume of the solution remains at 0.250 l , calculate the ph of the resulting solution. express your answer numerically to two decimal places. view available hint(s)

Sagot :

The pH of the solution is 9.14

For ammonia:

To calculate the amount of hydrogen gas collected, we use the equation given by ideal gas which follows:

PV = nRT

P= Pressure of the gas = 735 torr

V= volume of the gas = 7.70 l

T= Temperature of the gas= 22°C (22+273K) = 295K

R= Gas constant= 62.364 L torr/mol/K

n = number of moles of ammonia = ?

By substituting the values in the above equation, we get:

735×7.70 = n × 62.364 × 295

5659.5 = n × 18397.38

n= 5659.5/18397.38

n= 0.3076

For hydrochloric acid:

To calculate the number of moles for given molarity, we use the equation:

Molarity of the solution = [tex]\frac{moles of solute}{volume of solution}[/tex]

Molarity of hydrochloric acid = 0.400 M

Volume of solution = 0.250 L

Putting values in above equation, we get:

0.400= moles of solute/0.250

moles of hydrochloric acid = 0.1 mol

The chemical reaction for ethylamine and HCl follows the equation:

NH3+HCl---> NH4Cl

Initial:         0.316             0.18

Final:          0.136     -            0.18

volume of the solution = 0.250 l

To calculate the pOH of basic buffer, we use the equation given by Henderson Hasselbalch:

pOH = pKb + log([tex]\frac{salt}{base}[/tex])

pOH = pKb + log([tex]\frac{NH4Cl}{NH3}[/tex])

it is given:

pKb =  negative logarithm of base dissociation constant of ammonia =

-log(1.8 × [tex]10^{-5}[/tex]) = 4.74

[NH4Cl] = 0.18/0.450

[NH3] = 0.136/0.450

On substituting the values we get,

pOH= 4.74 + log ([tex]\frac{0.18/0.250}{0.136/0.250}[/tex])

pOH = 4.74 + 0.12

pOH= 4.86

pH + pOH= 14

pH= 14-pOH

    = 14-4.86

pH = 9.14

pH of the solution = 9.14

To learn more about calculating pH visit:

https://brainly.com/question/9278932

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