1a) Which of the following aqueous solutions are good buffer systems? . 0.19 M a

Question

1a) Which of the following aqueous solutions are good buffer systems?

. 0.19 M acetic acid + 0.11 M sodium acetate

0.39 M nitrous acid + 0.23 M sodium nitrite

0.30 M ammonium nitrate + 0.34 M ammonia

0.30 M perchloric acid + 0.23 M sodium perchlorate

0.19 M sodium hydroxide + 0.21 M sodium chloride

1b) Which of the following aqueous solutions are good buffer systems? .

0.26 M ammonium nitrate + 0.34 M ammonia

0.13 M acetic acid + 0.22 M sodium acetate

0.36 M hydrocyanic acid + 0.21 M potassium cyanide

0.24 M hydroiodic acid + 0.22 M potassium iodide

0.15 M sodium fluoride + 0.25 M hydrofluoric acid

1c) Which of the following aqueous solutions are good buffer systems? .

0.30 M ammonia + 0.40 M sodium hydroxide

0.20 M perchloric acid + 0.20 M potassium perchlorate

0.37 M potassium perchlorate + 0.29 M calcium perchlorate

0.20 M potassium hydroxide + 0.21 M potassium bromide

0.15 M acetic acid + 0.10 M potassium acetate

Explanation / Answer

1) a

A good Buffer consist of a weak acid +its conjugated base or a weak base+ conjugated acid

The acid /base conjugates should have similar concentration (within a factor of 10) so the buffering capacity is about the same for nuetralizing any strong acid or strong base added to the system

all the concentraion are within a factor 10 for the sysytem above so consider just compound

System Buffer

acetic acid + sodium acetate

CH3COOH =weak acid CH3COO-=conjugated base YES

Nitrous acid +    Sodium Nitrite YES

HNO2 =weak acid NO2 =Conjugated base

Ammonium Nitrate + Ammonia YES

NH4+ =Conjugated base NH3=Weak base

Perchloric acid + Sodium perchlorate NO

HClO4=Strong acid ClO4 = Conjugated Base   

Sodium Hydroxide + Sodium Chloride NO

NaOH = Strong Base NaCl = Nuetral Salt   

1 B

Ammonium Nitrate + Ammonia YES

NH4+ =Conjugated base NH3=Weak base

acetic acid + sodium acetate     YES

CH3COOH =weak acid CH3COO-=conjugated base

Hydrocyanic acid + Potassium cyanide      YES

HCN weak acid CN- Conjugated Base

Hydroiodic acid + Potassium iodide NO

HI Strong acid I-conjugated base

Sodium fluoruide Hydrofluoric acid YES

F-conjugated Base HF= weak acid

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