Given 0.10 M aqueous solutions of these salts, which solutions are acidic. Basic

Question

Given 0.10 M aqueous solutions of these salts, which solutions are acidic. Basic or neutral? a. NH4CIO4 b. NH4Cl c. RbCN d. Cs-CH3cOO e. BaBr2 f. FeCl2 g. KClO4 h. Na2CO3 i, KNO3 True or False a. A buffers solution tends to maintain a constant pH __________ b. A typical buffer is composed of a weak acid and its conjugate base conjugate base, or a weak base and it conjugate acid. __________ c. Buffers always produce solute ions having a high pH (> 7) _________ d. The best buffers are made mixing a strong base and a strong acid. _________ e. Maintain a constant pH when bases are added to them but not when acids are added to them. _________ Which of the following pairs of compounds could create a suitable buffer system? a. Sodium acetate and acetic acid b. ammonia and potassium hydroxide c. Sodium chloride and sodium hydroxide d. sodium sulfate and sodium hydroxide e. carbonic acid and sodium chloride

Explanation / Answer

9)

a) NH4ClO4 – Acidic (product of strong acid HClO4 and weak base NH3. Ammonium salts are acidic because in aqueous solution they can dissociate into ammonia and a proton. )

b) NH4Cl - Acidic (product of strong acid HCl and weak base NH3. Ammonium salts are acidic because in aqueous solution they can dissociate into ammonia and a proton.)

c) RbCN – Basic (products of strong base/weak acid.)

d) Cs-CH3COO - Basic (products of strong base/weak acid.)

e) BaBr2 – Neutral (the product of strong acid/strong base)

f) FeCl2 – Acidic (The cation comes from a weak base Fe(OH)2 and the anion comes from a strong acid HCl, the salt will be acidic. Most metals except 1A and 2A are weak acids.)

g) KClO4 – Neutral (The cation comes from a strong base KOH, and the anion comes from a strong acid HClO4, the salt will be neutral.

h) Na2CO3 - Basic (It shows basic character because when dissolved in water it produces NaOH (strong base) and H2CO3 (weak acid) so the resulting solution gets basic.)

i) KNO3 - Neutral (The cation comes from a strong base KOH, and the anion comes from a strong acid HNO3, the salt will be neutral.

10) Buffer are solutions that contain a weak acid and its conjugate base; as such, they can absorb excess H+ ions or OH- ions, thereby maintaining an overall steady pH in the solution.

a) A buffer is a solution that tends to maintain a constant PH --- TRUE

b) A typical buffer is composed of weak acid and its conjugate base or weak base and its conjugate acid.

TRUE

c,d and e are FALSE

11)

a) Sodium acetate and acetic acid

A buffer system can be made by mixing a soluble compound that contains the conjugate base with a solution of the acid such as sodium acetate with acetic acid. A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or mixture of a weak base and its conjugate acid,

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