3/23/2018 06:00 PM A 37.5/100 Print Calculator -Penodic Table estion 8 of 16 Inc
ID: 1027714 • Letter: 3
Question
3/23/2018 06:00 PM A 37.5/100 Print Calculator -Penodic Table estion 8 of 16 Inc Map Sapling Learning mL The flask shown here contains 0.541 g of acid and a few drops of phenolphthalein indicator contains 0.290 M NaOH. in water. The buret 10 10 What volume of base is needed to the end point of the titration? Numbe 35 13 mL base 20 Assuming the acid is monoprotic what is its molar mass? Add base to the solution unt it just turns pink. You may need to reset the litration if 144 g/ mol you go past the end point You may not have reached the end point of the iration yel, or you may be reading the volume in the buret incorrectly. Be sure to read the iquid level al the botom of the meniscus Once you see pink that fades away in the lask conimue adding base drop by drop unsi the pink color 5 16 17 18 f9 10 E |[3 /Explanation / Answer
1. As seen from the image above, the volume of NaOH needed to reach the end point of titration is 14 ml. We cannot find the volume of NaOH required theoretically. This is because the volume of the acid is unknown to us. Thus we cannot also find the no. of moles of acid. Thus the answer is based on the image provided.
Also we see the lower miniscus while taking the reading. Thus 14ml is correct and 13ml is not.
2. We know that at end point, the no. of moles of NaOH added is equal to the no. of moles of the acid as it is a monoprotic acid.
No.of moles of NaOH= molarity of NaOH × volume of NaOH used
= 0.029M × 0.014L= 4.06×10^-4 moles.
Mass of acid used= 0.541g.
No.of moles of acid=(mass of acid used)/(molar mass of the acid)
Molar mass of acid=(mass of acid used)/(no.of moles of acid)
= 0.541g/(4.06×10^-4)
=1332.51g.
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