Question

The next three (3) problems deal with the titration of 541 mL of 0.501 M carbonic acid (H2CO3) (Ka1 = 4.3 x 10-7, Ka2 = 5.6 x 10-11) with 1.5 M KOH.

3. How many mL of the 1.5 M KOH are needed to raise the pH of the original carbonic acid solution to a pH of 6.755? Give your answer to one decimal place.

Answer 1

Answer on Question #65481 - Chemistry - Inorganic Chemistry

The next three (3) problems deal with the titration of 541 mL of 0.501 M carbonic acid (H2CO3) (Ka1 = 4.3 x 10⁻⁷, Ka2 = 5.6 x 10⁻¹¹) with 1.5 M KOH.

3. How many mL of the 1.5 M KOH are needed to raise the pH of the original carbonic acid solution to a pH of 6.755? Give your answer to one decimal place.

Solution:

We find the concentration of carbonic acid:

$$c = \frac{n}{V} = \frac{0.501}{0.541} = 0.93$$

We find the pH of carbonic acid solution:

Using the law of mass action:

$$4.3 \times 10^{-7} = \frac{x^2}{(0.93 - x)}$$ $$x = 0.00063$$ $$pH = -\lg(x) = 3.2$$

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