Bases, Buffers, and Hydrolysis 6. Write the equation of HCO, acting as an acid:

Question

Bases, Buffers, and Hydrolysis 6. Write the equation of HCO, acting as an acid: 7. Write the equation of HCOs acting as a base: 18. Would the following salts produce a neutral (N), basic (B), or acidic (A) solution when dissolved in water? If not enough information is given to make the determination, explain what is needed and how you would use the information to make the determination Salt N, B, or A. If not enough information is given to make the determination, explain what is needed and how you would use the information to make the determination a. Na CO b. BeC20 c. NH Br d. BaFa e. KNO f. LicI 19. A buffer solution is composed of NaHCO, and Na co What is the purpose of a buffer solution? a. b. Using the buffer mentioned above, write the chemical reaction that occurs when a small amount of NaOH is added to this buffer. Using the buffer mentioned above, write the chemical reaction that occurs when a small amount of c. HCI is added to this buffer.

Explanation / Answer

Ans. #16. An acid donates a H+ to the aqueous system-

            HCO3-(aq) + H2O(l) ----------->H3O+(aq) + CO32-(aq)

#17. A base accepts a proton from the aqueous system-

            HCO3-(aq) + H2O(l) -----------> OH-(aq) + H2CO3(aq)

#18. A. Na2CO3 – It is a salt of strong base (NaOH) and week acid (H2CO3). The anion of such salts are conjugate base of the weak acid. Being a conjugate base, the anion (CO32) accepts a proton from the aqueous system to from OH-. Therefore, the resultant solution is BASIC in nature.

The cation (Na+) simply acts as spectator ion.

            Na2CO3(aq) --------> 2Na+(aq) + CO32-(aq)

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

#B. BeC2O4 is a salt is strong base and weak acid (H2C2O4). So, as explained in #A, the resultant solution would be BASIC.

#C. NH4Br is a salt of strong acid (HBr) and week base (NH3). The cation of such salts are conjugate acid of the weak base. Being a conjugate acid, the cation (NH4+) donates a proton to the aqueous system. Therefore, the resultant solution is ACIDIC in nature.

The anion (Br-) simply acts as spectator ion.

            NH4Br(aq) ------------> NH4+(aq) + Br-(aq)

            NH4+(aq) + H2O(l) ------> NH3(aq) + H3O+

#D. BaF2 is a salt is strong base and weak acid (HF). So, as explained in #A, the resultant solution would be BASIC.

#E. KNO3 is a salt of strong acid (HNO3) and strong base (KOH). A solution of such salts is NEUTRAL because both the cation and anion act as spectator ions.

#F. LiCl is a salt of strong acid (HCl) and strong base (LiOH). A solution of such salts is NEUTRAL because both the cation and anion act as spectator ions.

#19. A. The purpose of a buffer solution is to minimize the change in pH of the solution during a reaction or during addition of small quantities of acid or base.

#B. Addition of NaOH:

HCO3-(aq) + OH-(aq, from NaOH) -----> CO3-(aq) + H2O(l)

Note: CO32- can’t react with OH- because it doesn’t has a H+ to react with OH-.

#C. Addition of HCl

HCO3-(aq) + H+(aq, from HCl) -----> H2CO3(aq)

CO3-(aq) + H+(aq, from HCl) -----------> HCO3-(aq)

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