Chemistry, 18.03.2020 21:59 afifakiran5226
Phenolphthalein is an indicator that turns from colorless (acidic form) to magenta (basic form) and has a pKa of 9.40. What is the ratio of the magenta phenolphthalein concentration to the colorless phenolphthalein concentration ([magenta phenolphthalein]/[colorless phenolphthalein]) at a pH of 11?
Answers: 1
![pH=pK_a+\log(\frac{[salt]}{[acid]})](/tpl/images/0552/6240/e4eea.png)
![pH=pK_a+\log(\frac{[magenta(Php)]}{[Php]})](/tpl/images/0552/6240/ed1ee.png)
= negative logarithm of acid dissociation constant of phenolphthalein = 9.40![[magenta(Php)]](/tpl/images/0552/6240/398bf.png)
= concentration of magenta phenolphthalein![[Php]](/tpl/images/0552/6240/c3176.png)
= concentration of colorless phenolphthalein![11=9.40+\log(\frac{[magenta(Php)]}{[Php]})](/tpl/images/0552/6240/4797c.png)
![\log(\frac{[magenta(Php)]}{[Php]})=11-9.40=1.6](/tpl/images/0552/6240/3f9c3.png)
![\frac{[magenta(Php)]}{[Php]}=10^{1.6}=39.81 :1 \approx 40:1](/tpl/images/0552/6240/e1375.png)
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Phenolphthalein is an indicator that turns from colorless (acidic form) to magenta (basic form) and...
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