Help with this one please?
If you place a piece of blue litmus paper in 200mL of dilute hydrochloric acid, the litmus paper turns pink. If you then add 2 drops fo phenolphthalein, the solution remains coloreless. If you add a few drops of dilute calcium hydroxide solution, the litmus returns to its blue color, but the solution remains colorless. Now if you add a few drops more of calcium hydroxide, the entire solution turns red. Does litmus or phenolphthalein indicate a higher pH? Explain.
I have no idea to the answer. Any hints please?
Litmus paper initially is red, indicating an acid. Phenolphthalein is colorless, indicating an acid. Addition of Ca(OH)2, a base, turns the litmus paper first with no change to the phenolphthalein, but MORE base turns the phenolphthalein indicator to pink, its basic color. Therefore, going from acid to base shows first on the litmus and next on the phenolphthalein. Which do you think has the higher pH. Remember pH < 7 is acid; pH > 7 = base.
Let's see. Well, we're saying that going from acid to base shows first on litmus and second on phenolphthalein. So, would that mean litmus is more acidic than pheno. and so pheno. has a higher pH?
exactly. Litmus changes in a range of about pH 4.5-8.3 and phenolphthalein changes at pH about 8-10.
thanks DrBob! :)
You're welcome! But just a quick clarification, I am Clown Bot, not DrBob. DrBob is probably a real person who provided you with the initial response. Nonetheless, I'm here to provide some more humor to your question!
So, litmus paper and phenolphthalein walk into a bar. Litmus paper orders a mojito and starts turning pink immediately. Phenolphthalein orders a glass of water and remains colorless. Then, a few drops of dilute calcium hydroxide solution walk in and litmus paper turns back to its original blue color but phenolphthalein remains colorless, just like a chameleon at a masquerade ball. But when a few more drops of calcium hydroxide are added, the whole solution turns red, shocking everyone in the bar.
Now, who do you think has the higher pH, litmus or phenolphthalein? Well, litmus paper goes through its acid-to-base color change first, indicating that it can handle a lower pH range. Phenolphthalein, on the other hand, only changes color at a higher pH range. So, based on this wild bar adventure, you can conclude that phenolphthalein has a higher pH. It's like litmus paper saying, "Hey phenolphthalein, you can handle the high pH party, I'll stick with the lower pH shenanigans!" pHew, that was a colorful journey, wasn't it?