Question

please explain and show steps

V. 15.102. Predict which solution in each pair below will have the b. 1.00 X 10" M acetic acid (K = 1.76 X 10-5) or a. 2.56 102 M HCl or 4.09 x 10-2 MHBr lower pH. 1.00 x 10-5 M formic acid (K4 = 1.77 x 10-4) c. 22 mM CH3NH2 (pK6 = 3.36) or 22 mM(CH3)2NH (Kb = 5.9 x 10-4) d. 158 mM NH3 (pKo = 4.75) or 158 mM acetic acid (pK= 4.75) e. 0.00395 M HNO3 or 0.00145 M HC104 f. 2.05 x 10-2 M propionic acid (K, = 1.4 x 10-5) or 2.05 X 10-1 M fluoroacetic acid (K, = 2.6 X 10-3) g. 375 mM pyridine (pKp = 8.77) or 375 mM aniline (pKb = 9.40) h. 0.555 M Fe(H2O).3+ (K= 3 X 10-3) or 0.355 M Cr(H2O). (K2 = 1 X 10-4) 3+

Answer 1

As HOMEWORKLIB RULES rule we are allowed to solve maximum 4 parts of any question.

A) ph = -log(H+)

So, Ph increases when H+ decreases.

Ph of HCl = - log( 2.56 * 10^-2)

= 1.59

Ph of HBr = -log(4.09 * 10^-2)

= 1.38

Ph of HCl is lower.

B)

[H+] of weak acid = (Ka * c)^1/2

Ka of formic acid is greater than that of acetic acid.

So H+ of formic acid is higher

So ph of formic acid is lower .

C)

Pkb of CH3NH2 = 3.39

Kb = 4.07 * 10^-4.

Pkb of (CH3)2NH2 = -log kb = -log(5.9 * 10^-4)

= 3.23

[OH-] = (kb * c)^1/2

So, [OH-] of (CH3)2NH2 is higher.

So, POH of (CH3)2NH2 is less

So, Ph of (CH3)2NH2 is high.

D)

Pkb of NH3 = 4.75

Pka of CH3COOH = 4.75

so PKa of NH3 > Pka of CH3COOH

If PKa of CH3COOH is less , so PH of CH3COOH is also less.