If you dissolve K_2CO_3 in water, the potassium cation will act as a Lewis acid

Question

If you dissolve K_2CO_3 in water, the potassium cation will act as a Lewis acid toward water with a pKa of approximately 14, while the carbonate anion will act as a Bronsted Lowry base. Write equilibrium reactions as net ionic equations representing these two equilibria. Based on the pKa of the hydrated potassium cation and the pKb of carbonate, would the pH of a K_2CO_3 solution be acidic basic, or neutral? A buffer is prepared with 10.0 mL of 0.150 M formic acid (Ka = 1.80 times 10^-4) and 10.0 mL of 0.125 M sodium format solution. What the is pH of this buffer? Please provide the keyword(s) for the following three GHS safety symbols and briefly describe the precautions associated with each one.

Explanation / Answer

Q1.

note that K2CO3 will be diluted as follows:

K2CO3(s) --> K2COs(aq) --> 2K+ + CO3-2(aq)

note that in solution,

CO3-2(aq) + H2O(l) <--> HCO3-(aq) + OH-(aq)

as expected,

OH- will increase the pH, meaning that this is BASIC solution

Q2.

apply the buffer equation of henderson hasselbach:

pH = pKa + log(A-/HA)

where, pKa = -log(Ka) = -log(1.8*10^-4) = 3.744

A- = mol of formate

HA = mol of formic acid

so...

mmol of formate = MformV = 10*0.15 = 1.5 mmol

mmol of formic acid= MacV = 10*0.125 = 1.25 mmol

substitute in pH equation

pH = pKa + log(A-/HA)

pH = 3.744+ log(1.25/1.50)

pH = 3.6648

Q3.

GHS

the first sign (left) = CORROSIVE TO METALS caustic material, very reacting, irritant for skin/avoid contact with sking

the second sign ( middle) = ACUTE TOXICITY material may cause death

the last sign (right) = Respiratory sensitization, category

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.