Prelaboratory Assignment Answer the Prelaboratory Questions (these arc to be tur
ID: 905610 • Letter: P
Question
Prelaboratory Assignment Answer the Prelaboratory Questions (these arc to be turned in before beginning the lab). It is recommended that you have an additional copy ofyour Prelaboratory answers to assist you in your lab write-up. 1. You dissolve 0.239 g of acid in 25.0 mL of water. To react this acidic solution to the endpoint (use up the acid), you add 37.34 ml. of 0.1016 MNaOH. Determine the molar mass of the acid. 2. Which of the following will have to be exactly measured? Why? Which will not? Why? a. Volume of NaOH used b. Water added to acid c. Amount of indicator d. Mass of unknown acidExplanation / Answer
1) the acid is assumed to be monoprotic , (actually it should be mentioned )
acid n1M1V1 = n2M2V2 base
1 x (0.239/MM) x 1000 = 1 x (0.1016) x 37.34
MM = Molar mass of the acid = 62.9 = 63 may be its nitric acid
2) volume of NaOH and the mass of unkown acid is to be measured accurately so that we get correct results at end point, else we will add excess of NaOH
The amount of indicator and water would not affect the end point position so we can add without ,much accuracy