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A
B
100

TRUE or FALSE

A buffer consists of a strong acid and weak base

FALSE

Weak base and conjugate acid 

or

Weak acid and conjugate base

100

TRUE or FALSE

Adding NaOH to a solution of NaCl will make it more soluble

FALSE

Common ion effect

200

What is a polyprotic acid?

Any acid with 1 or more ionizable hydrogens

200

A precipitate forms when....

A) Q>Ksp     B) Q<Ksp     C) Q=Ksp

A

300

What is the solubility of Zn(OH)2 in a solution that is pH=7? (ksp=4.5e-17)

x=s=2.2e-6 M

Zn(OH)2 ⇔ Zn + 2OH

I                  0       0

C               +x     +2x
E                  x      2x

[Zn][OH]2 = (x)(2x)2 = 4x3

ksp=4x3 = 2.2e-6 M

300

Which of these is the most soluble

A) Ksp(CuCO3)=1.4×10-10     

B) Ksp(MgCO3)=3.5×10-8

C) Ksp(Zn3(PO4)2=9.0×10-33

B

Higher Ksp = More Soluble

400

You need to prepare a buffer with pH = 5.00. The conjugate acid-base pairs you have available are

A) HClO/NaClO (Ka, HClO = 2.9 x 10-8)

B) HCHO2/NaCHO2 (Ka, HCHO2 = 1.8 x 10-4) 

C) HC2H3O2/NaC2H3O2 (Ka, HC2H3O2 = 1.8 x 10-5 )

Which of the acid-base pairs should you use to make your buffer?

C

pka=-log(1.8 x 10-5 ) = 4.74

Within range of buffer capacity if pH = 5 

400

What is pH of a titration of 25mL of 0.1M HCl and 0.1M NaOH when no base is added?

pH = 1

strong acid -> plug directly into pH=-log[H]

pH = -log(0.1M)

500

Calculate titration of 100mL of 0.1M NH3 titrated w 50mL added of 0.1M HCl (kb=1.8e-5)

pH = 9.26

Moles

  • NH3 = 0.1*0.1L =0.010mol

  • H3O = 0.1*0.05L = 0.005mol

pH=pka

Find ka with kb 

pH=-log(ka)

500

Determine if AgI(s) is more soluble in acid solution than neutral solution (when acid is added)

Strong acid forms in products so it is not soluble in acid

AgI + H3O+ <=> HI + H2O + Ag+

(If a SA or SB forms in products, it prevents the precipitate rxn from occurring)