Respuesta :
Answer: The pH of the solution is 9.14
Explanation:
- For ammonia:
To calculate the amount of hydrogen gas collected, we use the equation given by ideal gas which follows:
[tex]PV=nRT[/tex]
where,
P = pressure of the gas = 735 torr
V = Volume of the gas = 7.90 L
T = Temperature of the gas = [tex]22^oC=[22+273]K=295K[/tex]
R = Gas constant = [tex]62.364\text{ L. torr }mol^{-1}K^{-1}[/tex]
n = number of moles of ammonia = ?
Putting values in above equation, we get:
[tex]735torr\times 7.90L=n\times 62.364\text{ L. torr }mol^{-1}K^{-1}\times 295K\\\\n=\frac{735\times 7.90}{62.364\times 295}=0.316mol[/tex]
- For hydrochloric acid:
To calculate the number of moles for given molarity, we use the equation:
[tex]\text{Molarity of the solution}=\frac{\text{Moles of solute}}{\text{Volume of solution (in L)}}[/tex]
Molarity of hydrochloric acid = 0.400 M
Volume of solution = 0.450 L
Putting values in above equation, we get:
[tex]0.400M=\frac{\text{Moles of hydrochloric acid}}{0.450L}\\\\\text{Moles of hydrochloric acid}=(0.400\times 0.450)=0.18mol[/tex]
The chemical reaction for ethylamine and HCl follows the equation:
[tex]NH_3+HCl\rightarrow NH_4Cl[/tex]
Initial: 0.316 0.18
Final: 0.136 - 0.18
Volume of the solution = 0.450 L
To calculate the pOH of basic buffer, we use the equation given by Henderson Hasselbalch:
[tex]pOH=pK_b+\log(\frac{[salt]}{[base]})[/tex]
[tex]pOH=pK_b+\log(\frac{[NH_4Cl]}{[NH_3]})[/tex]
We are given:
[tex]pK_b[/tex] = negative logarithm of base dissociation constant of ammonia = [tex]-\log(1.8\times 10^{-5})=4.74[/tex]
[tex][NH_4Cl]=\frac{0.18}{0.450}[/tex]
[tex][NH_3]=\frac{0.136}{0.450}[/tex]
pOH = ?
Putting values in above equation, we get:
[tex]pOH=4.74+\log(\frac{0.18/0.450}{0.136/0.450})\\\\pOH=4.86[/tex]
To calculate pH of the solution, we use the equation:
[tex]pH+pOH=14\\pH=14-4.86=9.14[/tex]
Hence, the pH of the solution is 9.14
