Hello I need some help with my lab and was wanting to see if I\'m doing this rig

Question

Hello I need some help with my lab and was wanting to see if I'm doing this right so far. I'm not too sure if I did the first question right and I'm stuck on the second question of experiment 1. How do you know what the pH is of the indicators?

Experiment 1

1.   Calculate the concentrations of H3O+ and the pH of each acidic solution. Since HCl is a monoprotic acid (an acid that donates only one proton or hydrogen atom permolecule to an aqueous solution), the H3O+ concentration is equivalent to the HCl molarity. Summarize your results for each pH indicator, recording both the pH values and the color of the solution at each pH.

Tube 1: (.1 Molar HCl)(5mL water) = (?)(10mL-total volume)

2. Estimate the useful range for each indicator, from a minimum to maximum pH. The range usually spans 1.5 to 2 pH units. For example, bromphenol blue is considered to be useful in the range from 3.0 to 4.6.

The first one is done for you...

3. Which indicator is the best to use for observing pH changes around pH = 2, pH = 4 and pH = 6?

Tube # [H3O+] pH bromothymol blue methyl yellow bromocresol green red cabbage extract 1 .05M 1.35 yellow dark red yellow red 2 .045M 1.35 yellow dark red yellow red 3 .0405M 1.39 yellow bronze yellow purple redish 4 .03645M 1.44 yellow yellow green light purple 5 .032805M 1.48 yellow yellow blue dark purple 6 .0295245M 1.53 green yellow blue blueish purple 7 .02657205M 1.58 light greenish blue yellow blue blue

Explanation / Answer

Answer:

2)

3)

pH=2 : Methyl Violet

pH=4 : methyl orange

pH=6 : bromothymol blue

for more information visit:

http://crescentok.com/staff/jaskew/isr/chemistry/indi_color.htm

Indicator pH bromothymol blue 6-7.5 Congo red 3-4.5 Bromocresol Green 4-5.5 Methyl orange 2-4

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