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name Prelaboratory Assignment: Enthalpy of Neutralization 1. 50.0 mL of 0.180 M

ID: 561088 • Letter: N

Question

name Prelaboratory Assignment: Enthalpy of Neutralization 1. 50.0 mL of 0.180 M sodium hydroxide solution is added to 50 mL of 0.200 M lactic acid solution. The reaction goes to completion. It can be written a. What is the limiting reactant. How many moles of it were used? b. The system can be regarded as 100 g of water, C,- 4.184J-K g. Calculate the heat capacity of the system. C. The initial temperature of the system is 22.478C; the final temperature is 23.67 Calculate the amount of heat absorbed by the system. d. Calculate the amount of heat released by the reaction. e. Calculate the molar enthalpy of neutralization for lactic acid.

Explanation / Answer

1. a. no of mol of NaOH solution = 50*0.18 = 9 mol

   no of mol of lactic acid = 50*0.2 = 10 mol      

limiting reactant = NaOH

b. heat capacity(C) = Cg*m

                      = 4.184*100

                      = 418.4 j/k

   c. amount of heat absorbed by the system(q) = C*DT

                     = 418.4*(23.67-22.47)

                   = 502.08 joule

    d. amount of heat released by the reaction = 502.08 joule

     e. molar enthalpy of neutralisation of lacticacid

                     = -q/n = -0.502/0.009

                     = -55.78 kj/mol