Two solutions, initially at 24.60*C, are mixed in a coffee cup calorimeter (Ccal

Question

Two solutions, initially at 24.60*C, are mixed in a coffee cup calorimeter (Ccal = 15.5 J/*C). When a 100.0 mL volume of 0.100 M AgNO3 solution is mixed with a 100.0 mL sample of 0.200 M NaCl solution, the temperature in the calorimeter rises to 25.30*C. Determine the DH*rxn for the reaction as written below. Assume that the density and heat capacity of the solutions is the same as that of water.

            NaCl(aq) + AgNO3(aq)--------AgCl(s) + NaNO3(aq)    DH*rxn = ?

Answer is -69 kJ. Please show a step by step solution and make clear where each number came from. I saw a lot of answers to this equation but most were wrong or had numbers that seem to appear out of nowhere to get the correct answer. Thank you for the help.

Explanation / Answer

moles of AgNO3 = 100 x 0.1 / 1000 = 0.01

moles of NaCl = 100 x 0.200 / 1000 = 0.02

volume of solution = 100 + 100 = 200 mL

mass of solution = 200 x 1 = 200 g

temperature rise = 25.30 - 24.60 = 0.70 oC

Q = m Cp dT + Cp dT

   = 200 x 4.184 x 0.70 + 15.5 x 0.70

Q = 596.61 J

NaCl(aq) + AgNO3(aq)--------> AgCl(s) + NaNO3(aq)

1                  1                       1

0.02 0.01

delta H = - Q / n

   = - 596.61 x 10^-3 / 0.01

delta H = - 59.66 kJ

Note : the answer is - 59.6 kJ . may be the answer you given is wrong. check it once

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