Question

# Find the pH for the following solutions: a) A solution that is 0.115 M in HBr...

Find the pH for the following solutions:

a) A solution that is 0.115 M in HBr and 0.130 M in HCHO2

b) A 0.25 M CH3NH3I solution? (Kb = 4.4 x 10-4 M for CH3NH2)

c) A 0.0180 M solution of HClO2? (Ka = 1.1 x 10-2 M)

d) A 0.0180 M solution of Sr(OH)2

e) A 0.170 M solution of KOCl? (For HOCl, Ka = 3.5 x 10-8 M)

f) A solution that is 3.00×10−2M in HI and 9.00×10−3M in HF. (For HF, pKa = 3.14)

g) A solution that is 0.105 M in KF and 0.105 M in KCl? (for HF, pKa = 3.14)

I'm having a hard time in chem class, please help understand how to know if it's an acid or base, and what the steps are to find pH. Thanks!

solution:

a)

b)

0.25 M CH3NH3I

it is a salt oe weakamine,strongacid.So that it is acidic.

pH = 7-1/2(pkb+logC)

pkb of CH3CH2NH2 = 3.19

= 7 - 1/2 (3.19+Log(0.25))

= 5.7

c)

HClO2 + H2O ---> H3O+ + ClO2-

ka = [H3O+] [ClO2-] /[HClO2]

1.1*10-2= [x][x]/[0.15]

1.1*10-2*0.15= x2

0.00165 = x2

taking square rrot of boht the sides we get x= 0.0406 M

x = [H3O+] = [H+]

so, pH = - log[H+]

pH = - log[0.0406] = 1.34

d)

Sr(OH)2--------> Sr2+ + 2OH-

so, [OH-] =2*0.018

[OH-] = 0.036 M

so pOH = -log[OH] = - log[0.036]

pOH = 1.44

so, Ph = 14 - pOH = 14 - 1.44

pH = 12.6

=13.7

#### Earn Coins

Coins can be redeemed for fabulous gifts.