Q3 ESTION 1 Vhich indicator would be the best to use for a titration between O 1
ID: 1026318 • Letter: Q
Question
Q3 ESTION 1 Vhich indicator would be the best to use for a titration between O 1 thymol blue, color change at plt 13 O 2 phenolphthalein, color change at pH 8-10 O 3 bromothymol blue, color change at pH 6-8 O 4.methyl red, color change at pH 3-5 O 5 alizarin yellow R, color change at pH 10-12 0 20 M HNO3 with 0.10 M KOH? You wll probably need to consut the appropriate table in the book QUESTION2 Calculate the pOH of a solution that is 0 339 M CHjCOOH and 0.2 M CH3COONa. Ka of CH3COOH is 1.8 x 105 Enter your answer with two decimal places QUESTION Theph. of a 0 50 M soit on offor m c acid-202. Calculate the change in pH when 1 4 g of HCOONa is added to 30 mL o050 M forme acid HCOOHignore any charges nok value for HCOOH is 1.8x 104 eme K. Click Save and Submit to save and submit. Click Save All Answers to save all ansvers SAVE ALL ANSWERS CLoExplanation / Answer
Solution (3) :- Formic acid is a weak acid, When sodium formate is added to it, a buffer solution is formed. pH of the buffer solution could be calculated using Handerson equation.
Moles of sodium formate added = 1.4 g x (1mol/68.01g) = 0.0206
moles of formic acid = 38.0 mL x (1L/1000 mL) x (0.50 mol/L) = 0.019
pKa = - log Ka
pKa = - log(1.8 x 10-4)
pKa = 4.74
pH = pKa + log(base/acid)
pH = 4.74 + log(0.0206/0.019)
pH = 4.74 + 0.035
pH = 4.78
Change in pH = 4.78 - 2.02 = 2.76
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