1. What is the function of a buffer? 2. How does the capacity of a buffer relate
ID: 1046691 • Letter: 1
Question
1. What is the function of a buffer? 2. How does the capacity of a buffer relate to its concentration? 3. Calculate the quantity, in a buffer that h grams, of formic acid and sodium formate necessary to make 500. mL of as a formic acid concentration of 0.75 M and a sodium formate concentration of 0.75 M. You will need to look up or calculate the molar masses of these two compounds as See question 5 below for their chemical formulas. 4. A student tried to make a buffer of pH 4.0 using sodium acetate and acetic acid. The initial pH of the buffer solution was 3.9. How should the student adjust the pH to the desired value? 5. What is the pH of the buffer described in Question 3? The formic acid (HCHO2) concentration is .75 M, the sodium formate (NaCHO) concentration is 0.75 M, and the pK, of formic acid is 3.74 2016 Cengage Leaning All Rights Reserved. May not be scanned, copied or duplicated,or posed to a publicly accessible website, in whole or in part 1Explanation / Answer
1. A buffer is a substance which can't alter its pH even by additng small amounts of either acid or a base.
2. The capacity of buffer related to concentration of [H+]/[OH-]. By adding small amounts of acid or a base increases or decreases the above concentrations. If the concentration of H+ increases/decreases,the capacity of buffer indicates through showing its standard pH.
3. The mass of HCOOH = (0,5 L)*(0.75 mol/L)(46.03 g/mol) = 17.26 g
The mass of HCOONa = (0.5 L)*(0.75 mol/L)(68.01 g/mol) = 25.5 g
4. The pH value is increasing from 3.9 to 4.0. It is indicating that the concentration of H+ is decreased. Hence, to get the desired pH add trace amount of a strong base.
5. According to Henderson's -Hasselblach equation -
pH = pKa + log [HCOO-/HCOOH]
= 3.74 + log (0.75/0.75) = 3.74
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.