ONLY 11, 12, 13, 14. THANKS! The calorimeter above was used to determine the ent

Question

ONLY 11, 12, 13, 14. THANKS!

The calorimeter above was used to determine the enthalpy of the reaction between hydrochloric acid and sodium hydroxide. The relevant temperatures at the time of reaction (assuming the reaction was instantaneous) were determined as above. Temperatures were recorded as a function of time and extrapolated to the time of mixing. The generic graph is shown below. The temperature axis is again intentionally not displayed. The relevant information is given in the table below.

The data for the reaction between HCl and NaOH were as follows:

If the temperatures of the acid and base at the time of mixing are different, use their average as the temperature of the mixture before reaction. Use the average also as the initial temperature of the calorimeter.

Question 5

What is the limiting reagent?

A. HCl

B. NaOH

C. The number of moles of acid and base are equal

Enter Your Answer:      A     B     C       A Correct

Question 6

How many moles of the limiting reagent reacted?

Enter Your Answer:        .113moles Correct

Question 7

What is the average temperature of the mixture of HCl and NaOH at 3.00 min (before they have reacted)?

Enter Your Answer:        23.9C Correct

Question 8

What is the weight of the reaction solution in grams?

Enter Your Answer:        107.1grams Correct

Question 9

What is the change in temperature experienced by the reaction mixture (and the calorimeter) extrapolated back to the time of mixing?

Enter Your Answer:        15C Correct

Question 10

How much of the heat liberated by the reaction (in kJ) went to heating up the reaction solution?

Enter Your Answer:        6.38kJ Correct

Question 11

How much of the heat liberated by the reaction (in kJ) went to heating up the calorimeter?

Enter Your Answer:        72.9kJ Incorrect

Question 12

What is the enthalpy change (in kJ) for the reaction? (Pay attention to the sign!)

Enter Your Answer:        -5.9kJ Incorrect

Question 13

This question explores the impact of the calorimeter constant on the final result.

What percent of the total enthalpy of the reaction is absorbed by the calorimeter?

Enter Your Answer:     

Question 14

What is the molar enthalpy, Hneut, of the reaction in:

H+ (aq) + OH- (aq) H2O (l)

in kJ/mol?

Enter Your Answer:        -285.8 kJ/mol Incorrect

Value Units Concentration of HCl 2.26 M Volume of HCl 50.0 mL Density of HCl 1.02 g/mL Concentration of NaOH 2.28 M Volume of NaOH 55.0 mL Density of NaOH 1.02 g/mL Specific Heat of HCl & & NaOH & Reaction Mixture 3.97 J/g-K Temperature of HCl at 3.0 min, Tacid (from graph) 23.9 oC Temperature of NaOH at 3.0 min, Tbase (from graph) 23.9 oC Temperature of reaction mixture at 3.0 min, Tmix  (from graph) 38.9 oC

Explanation / Answer

HCl + NaOH ----> NaCl + H2O

nO of mol of HCl = MV = 2.26*50/1000 = 0.113 mol

nO of mol of NaOH = 2.28*55/1000 = 0.1254 mol

from equation

1 mol HCl = 1 mol NaOH

5. limiting reactant = HCl

answer: A

6. nO of mol of HCl reacted = 0.113 mol

7. average = 23.9 c

8. weight of reaction solution = weight of HCl + NaOH

   = 50*1.02+55*1.02 = 107.1 grams

9.   temperature experienced by the reaction mixture

    = 15 c

10.   q = msDT

        = 107.1*3.97*15

        = 6.38 KJ

11. i think it is coffecup calorimeter. then heat released is

   equal to heat gained by calorimeter.

   qcal = 6.38 kj

12. enthalpy change = -6.38 kj

13. i think it is 100% . because it is a coffe cup calorimeter. provided

heat do not lost to surroundings.

14. DHrxn = -6.38/0.113 = -56.46 kj/mol

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