Lemon juice normally has a pH of $$2$$. If all the acid in the lemon juice is citric acid and there are no citrate salts present, then what will be the citric acid concentration [HCit] in the lemon juice ? $$(Assume$$ that only the first hydrogen of citric acid is $$important)HCit$$ ⇌ $$H+$$ $$+$$ $$Cit-$$, $$Ka=8.4$$ × $$10-4$$ mol $$L-1$$

Question

Lemon juice normally has a pH of $$2$$. If all the acid in the lemon juice is citric acid and there are no citrate salts present, then what will be the citric acid concentration [HCit] in the lemon juice ? $$(Assume$$ that only the first hydrogen of citric acid is $$important)HCit$$ ⇌  $$H+$$ $$+$$ $$Cit-$$,     $$Ka=8.4$$ × $$10-4$$  mol  $$L-1$$

Infinity Learn · Accepted Answer

$$H+$$ $$=$$ KaC,  $$pH=2$$,    ∴    $$H+$$ $$=$$ $$10-2$$ $$M10-2$$ $$=$$ $$KaC10-4$$  $$=$$  $$8.4$$ × $$10-4$$ × C ∴            C $$=$$ $$11.9$$ ×  $$10-2$$ M

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