FRQ (Show all work for full credit) A student wants to determine the Molarity of an unknown solution of LiOH To determine this, the student measures ou 50mL of 0.5M H_(2)CO_(3) The student adds the LiOH to the acid until a faint pink color appears. The student checks the buret and calculates that 34.45mL of the LiOH were added. 1. How many moles of H+ were in the flask before the base was added? (3pts.) 2. What is the pH of the acid before the addition of LiOH? (2pts.) 3. At the moment the pink color appears, how many moles of LiOH have been been added to the flask? (2pts.) 4. Given all of the data gathered from the titration,what is the Molarity of the LiOH? (3pts.)

Question

FRQ (Show all work for full credit) A student wants to determine the Molarity of an unknown solution of LiOH To determine this, the student measures ou 50mL of 0.5M H_(2)CO_(3) The student adds the LiOH to the acid until a faint pink color appears. The student checks the buret and calculates that 34.45mL of the LiOH were added. 1. How many moles of H+ were in the flask before the base was added? (3pts.) 2. What is the pH of the acid before the addition of LiOH? (2pts.) 3. At the moment the pink color appears, how many moles of LiOH have been been added to the flask? (2pts.) 4. Given all of the data gathered from the titration,what is the Molarity of the LiOH? (3pts.)

Answer 1

1. To determine the number of moles of H+ in the flask before the base was added, we need to use the formula:Moles = Molarity x VolumeGiven that the molarity of the H2CO3 solution is 0.5M and the volume is 50mL (or 0.05L), we can calculate the moles of H+ as follows:Moles = 0.5M x 0.05L = 0.025 molesTherefore, there were 0.025 moles of H+ in the flask before the base was added.2. To calculate the pH of the acid before the addition of LiOH, we need to use the formula:pH = -log[H+]Since the concentration of H+ is 0.025M, we can calculate the pH as follows:pH = -log(0.025) = 1.60Therefore, the pH of the acid before the addition of LiOH is 1.60.3. At the moment the pink color appears, the solution is neutral, meaning the moles of H+ and OH- are equal. Since the moles of H+ were 0.025 moles, the moles of LiOH added must also be 0.025 moles.4. To determine the molarity of the LiOH, we can use the formula:Molarity = Moles / VolumeGiven that the moles of LiOH added were 0.025 moles and the volume of the LiOH solution added was 34.45mL (or 0.03445L), we can calculate the molarity of the LiOH as follows:Molarity = 0.025 moles / 0.03445L = 0.724MTherefore, the molarity of the LiOH is 0.724M.

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