1. Discuss the relative buffering abilities of solutions 1a-5a when challenged b
ID: 711853 • Letter: 1
Question
1. Discuss the relative buffering abilities of solutions 1a-5a when challenged by the addition of 0.3 mL of acid. Be sure to also compare the solutions to the negative control, water (solution 6a).
2. Discuss the relative buffering abilities of solutions 1b-5b when challenged by the addition of 0.3 mL of base. Be sure to also compare the solutions to the negative control, water (solution 6b).
Volume water Solution Volume Volume Expected Measured Challenge pH after pH 6 6 6.5 6.5 PH (0.3 ml) challenge 5.83 5.99 6.45 8.77 8.77 6.85 6.85 3.9 3.9 1.6 1.6 0.5 0.5 0 0 1.23 1.23 3.15 3.15 6.1 6.1 8.4 8.4 9.5 9.5 0 0 mL 10 10 10 10 10 10 10 10 10 10 20 20 3.02 +0.5 0.69 +0.68 0.49 +0.51 0.38 +3.05 0.75 +2.93 6.48 +3.1 2.81 6.49 5.76 1b 2a 2b 3a 3b 1 M HCI 1M NaOH 1 M HCI 6.42 1M NaOH7.11 1 M HCI 7.001M NaOH7.51 1 M HCI 7.29 6.80 7 7.5 7.5 7.55 7.75 8.24 8.47 8.40 8.47 7.17 1M NaOH 10.80 7.49 1M NaOH 11.40 1.92 IM NaOH11.57 4b 5a Sb 1 M HCl E7 1 M HCl1 6bExplanation / Answer
looking at the data you can say component A is a strong acid and component B is its weak conjugate base
1. from 1a to 5a lets analyize
in 1a the quantity of A is more and B is less. nitial pH is in the acidic range. when 1M HCl is added the pH drops a huge amount (-3.02). this means it was not able to neutralise the acid properly
now as you move towards 5a, in every step you increase amount of B while decreasing A and you see the pH is drop decreases which means B is basic in nature.
And it can be concluded that from 1a to 5a the buffering abilities or buffer strength increases and all of them are very much better than water because in water the pH drops very steeply. almost the whole solution becomes acidic!
2. Now, from 1b to 5b.
In 1b if you see after adding 1m NaOH the change is pH is very less (just 0.5!). which means 1b is a perfect buffer and was able to neutralise almost all the base. in 1b the amount of A is more so it can also be concluded that component A is not only acidic in nature but is a strong acid since it was able to neutralise almost all NaOH which is also a strong base.
As you go towards 5b, decreasing the amount of A and increasing B results in larger pH change. the buffering abilities decrease from 1b to 5b.
Also, if you notice solution 4b and negative contol 6b(water) have almost same buffering strength. both show equal change in pH!
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