Question

1a)Calculate the pH of 50mL of 0.750M hydrazine (N2H4, Kb=3.0×10-6) mixed with 32mL of 0.750M HCl. b) Calculate the pH of a solution of 50mL of 0.075M HCl mixed with 50mL of 0.050M NaOH c) Calculate the pH of a solution of 100mL of 0.250M acetic acid, ka=1.8×10-5, mixed with 50mL of 0.500M NaOH.

Please show your work so I can actually learn/understand how to do this! Thank you!!

Answer 1

1.a ) No. of moles in 82 mi ( 50 + 32 ) HCL sol = 0.750 / 1000 x 32 =0.024 mole

No of moles of hydrazin salt of 82 ml sol = 0.750 / 1000 x 50 = 0.0375 moles

pH = -log Kb + log [salt ] / [ acid ]

= - log 3 x 10^-3 + log 0.0375 / 0.024

= 2.5228 - 0.1931 = 2.3297

b ) No. of moles in 100 ml ( 50 + 50 ) HCL sol = 0.075 / 1000 x 50 =0.00375 mole

No of moles of salt of 100 ml sol = 0.050/ 1000 x 50 = 0.0025 moles

pH = -log Ka + log [salt ] / [ acid ]

= 1.8 x 10^-5 + log 0.0025 / 0.0037

= 4.7447 - 0.1703 = 4.5744

c )

No. of moles in 150 ml ( 100 + 50 ) of acetic acid sol = 0.250 / 1000 x 100 =0.025 mole

No of moles of salt of 150 ml sol = 0.500 / 1000 x 50 = 0.025 moles

pH = -log Ka + log [salt ] / [ acid ]

= 1.8 x 10^-5 + log 0.025 / 0.025

= 4.7447 - 0 = 4.7447