3. 50 ml so g) of L.O M HCI is mised with so ml (- 50 g) of 1.0 M NaOH in a calo

Question

3. 50 ml so g) of L.O M HCI is mised with so ml (- 50 g) of 1.0 M NaOH in a calorimeter. The initial temperature of HCI and NaOH is 25.rcThe heat frorn the reaction is contained in the calorimeter to warm up the mixture, and the final temperature of the solution is 44.0 C. The specific heat ofthe solution is 4.18J/gand the calorimeter constant C 23.5J/C. a. Write the reaction equation. b. How many moles of HCI (or NaOH) are used in the reaction? c. Calculate the molar reaction heat AH A hot pack contains 100 ml salt solution, and it should reach a maximum of 65°C. A cold pack contains 100 ml salt solution, and it should reach a minimum of 0 °C. In an experiment, 1 gram NH,NO, is dissolved in 30 ml water in a Styrofoam cup. The dissolution causes solution temperature being reduced from 22.5 to 20.4 , 4. (a) Can NHNO, be used as hot pack or cold pack? (b) How many grams of NH NO, are needed for making one pack?

Explanation / Answer

Q3

a)

HCl + NaOH = NaCl + H2O

b)

ratio is 1:1

mol of HCl = MV = 1*50*10^-3 = 0.05 mol of HCl and 0.05 mol of NaOH used

c)

HRxn = Qrxn/n

Qrxn = Qsolution + Qcal = m*C*dT + Ccal*dT = (m*c + Ccal)*dT

Qrxn = (50*4.18 + 23.5)*(44-25) = 4417.5 J

HRxn = -4417.5 /(0.05) = -88350 J/mol = -88.35 kJ/mol

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