Late Nite Labs 3 - LateNiteLabs pHIndicators Chemistry...

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Unformatted text preview: 7/20/2016 Late Nite Labs pH Indicators Chemistry pH 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 [H3O+] pH bromothymol blue methyl yellow bromocresol green Yellow Red Yellow Yellow Red Yellow Yellow Orange Yellow Yellow Yellow Green Yellow Yellow Light Blue Green Yellow Blue Light blue Yellow Blue 2 3 4 5 6 7 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. pH bromothymol blue 3.0­4.6 methyl yellow 2.0­5.0 bromocresol green 5.5­8.0 red cabbage extract 1­12 3. Which indicator is the best to use for observing pH changes around pH = 2, pH = 4 and pH = 6? Experiment 2 1. Calculate the concentrations of OH­ and the pH of each basic solution. Since NaOH donates one OH­ ion for each NaOH molecule, the OH­ concentration is equivalent to the NaOH molarity. The pOH is calculated as ­log[OH­] and the pH is calculated as 14 ­ pOH. Summarize your results for each pH indicator, recording both the pH values and the color of the solution at each pH. Tube # 1 2 [OH­] pOH pH bromothymol blue red cabbage extract Yellow Red Yellow Red 3 Purple 1/2 7/20/2016 Late Nite Labs 4 5 6 7 Yellow Green Purple Blue Purple Blue Purple Blue Blue 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, metacresol purple is considered to be useful in the range from 7.4 to 9.0. pH bromothymol blue red cabbage extract alizarin yellow phenolphtalein 3. Which indicator is the best to use for observing pH changes around pH = 7, pH = 8, pH = 10 and pH = 12? 2/2 ...
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