Chemistry question/homework??

Posted on 2016-11-16 18:50:00 in Chemistry by JACK MILE

1. Hydrothermal vents in the ocean offer a unique environment for growth in which only specialist organisms, such as the Pompeii worm, may grow due to the extreme temperature, pressure and pH conditions as well as the range of 
toxic chemicals found. To simulate the 
conditions near a particular ocean vent, an aquatic chemist wishes to make a solution in which the pH will be held constant at 2.50. The following materials are available. 

I. 2.00 L of a starting solution, 1.25 mol L–1 chloroacetic acid (ClCH2COOH, pKa 
= 2.85) and solid sodium chloroacetate (ClCH2COONa, molar mass 116.48 g mol 
–1) 
II. 2.00 L of a starting solution, 1.25 mol L–1 nitrous acid (HNO2, pKa 
= 3.15) and solid sodium nitrite (NaNO2 
, molar mass 69.00 g mol–1) 

III. 2.00 L of a starting solution, 1.25 mol L–1 acetic acid (CH3COOH, pKa 
= 4.74) and solid sodium acetate (CH 
3COONa, molar mass 82.04 g mol–1) 

a) Which buffer system would best suit the needs of the scientists studying hydrothermal vents? 

i-chloroacetic acid/sodium chloroacetate 
ii. nitrous acid/sodium nitrite 
iii. Acetic acid/sodium acetate 

b) What concentration of the conjugate base (ie depending on your answer to part a: ) is required to produce an appropriate buffer using the starting solution given? 
c) What mass (grams) of the solid is required to produce an appropriate buffer using the starting solution given? 

Thank you.

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