Data Table 4-Unbuffered/Buffer Comparisons # drop HCI | # drop NaOH | Change pH
ID: 1039312 • Letter: D
Question
Data Table 4-Unbuffered/Buffer Comparisons # drop HCI | # drop NaOH | Change pH in | % Change in pH pH Beaker 10 (unbuffered) Beaker 1 10 (unbuffered) Beaker 20 (unbuffered) Beaker 20 (unbuffered) 100 % 10 93, in|% Change in 3 # drop HCI| # drop NaOH Change pH pH Beaker 30 (buffered) Beaker 3 10 (buffered) Beaker 4 0 (buffered) Beaker 40 (buffered) 7 10 0 Buffer solutions were prepared by blowing exhaled breath into the sodium bicarbonate solution through a straw. Discussion Questions 1. Did the buffer system work? Answer this question by comparing data of % change in pH (control vs. sample). 2. What is the purpose of blowing exhaled breath into the 0.1 M NaHCO, solution? Write the chemical reaction equation. 3. Write a chemical reaction equation for how this buffer acts when 10 drops of 1.0 M HCI solution is added. Explain, with data, why there is no significant change in pH.Explanation / Answer
1) Let's do the comparison of unbuffered and buffered solution:
When we add 10 drops of HCl to the unbuffered solution, there is a 100% change in pH from 7 to 0.
And when we add 10 drops of NaOH to the unbuffered solution, change in pH is 43% from 7 to 10.
Thus addition of acid and base makes pH change drastically.
Now, when we add 10 drops of HCl to the buffered solution, there is a 22% change in pH from 9 to 7.
and when we add 10 drops of NaOH to the buffered solution, change in pH is 0% keeping constant at 9.
Thus, buffer works to keep pH of solution a its original pH (9) in case of addition of NaOH, however there is slight change in pH when we add acid to the solution. Overall, we can say buffer works with addition of base or acid.
2) When we blow exhaled breath into NaHCO3 solution we are actually adding CO2 to the solution, and when CO2 combines with water it makes H2CO3 weak acid (which act as a buffer!) Below is the chemical reaction:
CO2 + H2O --> H2CO3
3)
Effect of addition of H+(acid):
H+ + HCO3- --> H2CO3
adding an acid to the buffer creates more of the acidic component already present in the buffer.
Effect of addition of OH-(base):
OH- + H2CO3 --> H2O + HCO3-
adding a base to the buffer produces more of the bicarbonate ion, the basic component of the buffer.
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