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pH Indicators for Solutions


You took 7 test tubes. In one you mixed 5ml of 0.1M HCI and mixed 5ml of water together. You add 9ml of water to the other 6 test tubes. If you take the original test tube (the one that you mixed 5ml of 0.1M HCI and 5ml of water) and put 1ml into test tube #2. If you took test tube #2 and put 1ml into test tube #3 and soon (repeat till all are done). Add 2 drops of Bromothymol Blue to all 7 test tubes.


1. Calculate concentrations of H30+ and the pH of each acidic solution. Since HCl is a monoprotic acid, the H30+ concentrations are equivalent to HCl. First do equation: (M con)(V con)=(M dil)(V dil)

2. Next, substitute known values

3. M dil=______M

4. Once you find the concentration, find the pH using the formula:
pH= -log[H2O+]

5. Repeat the procedure above using Methyl yellow as the indicator.

6. Repeat the procedure above using Bromcresol Green as the indicator.

7. Repeat the procedure above using Red Cabbage Extract as the indicator.

Thank you! I REALLY appreciate it!

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Solution Preview

The first test tube has a 5ml of 0.1M HCl.
Use the equation: M1*V1 = M2*V2
M1 = initial conc of Hcl = 0.1M
V1 = initial volume = 5ml = 0.005L
V2 = total volume = 5ml + 5ml = 10 ml = 0.01L
M2 = Final concentration of HCl (what we are looking for)

M1*V1 = M2*V2
(0.1M)*(0.005L) = (M2)*(0.01L)
M2 = (0.1M)*(0.005L) / 0.01L
M2 = 0.05 M


Solution Summary

This solution discusses pH indicators for solutions.