Two solutions,initially at 24.69°C,are mixed in a coffee cup calorimeter.When a 200.0 mL volume of 0.100 M AgNO₃ solution is mixed with a 100.0 mL sample of 0.100 M NaCl solution,the temperature in the calorimeter rises to 25.16°C.Determine the DH°_rxn,in units of kJ/mol AgCl.Assume that the density and heat capacity of the solutions is the same as that of water.Hint: Write a balanced reaction for the process. A) -32 kJ/mol AgCl B) -78 kJ/mol AgCl C) -59 kJ/mol AgCl D) -25 kJ/mol AgCl E) -62 kJ/mol AgCl

Question

Quizplus · Accepted Answer

The balanced chemical equation for the reaction between AgNO3 and NaCl is:

AgNO3 (aq) + NaCl (aq) → AgCl (s) + NaNO3 (aq)

The reaction involves the formation of 1 mole of AgCl.

The heat (enthalpy) change for the reaction can be calculated using the equation:

ΔHrxn = -(qrxn)/(moles of AgCl)

where qrxn is the heat absorbed by the solution and can be calculated using:

qrxn = (mCΔT)

where m is the mass of the solution (assumed to be 300 g), C is the specific heat capacity of the solution (assumed to be 4.18 J/g•°C), and ΔT is the temperature change (0.47°C).

Substituting the values gives:

qrxn = (300 g) × (4.18 J/g•°C) × (0.47°C) = 587.94 J

The number of moles of AgCl produced is calculated using the initial concentration of AgNO3:

moles of AgNO3 = (0.100 mol/L) × (0.200 L) = 0.0200 moles

Since the stoichiometry of the balanced equation is 1 mole of AgCl, the moles of AgCl produced is also 0.0200 moles.

Substituting the values into the equation for ΔHrxn gives:

ΔHrxn = -(587.94 J)/(0.0200 moles) = -29,397 J/mol

Converting to kilojoules gives:

ΔHrxn = -29.397 kJ/mol

Rounding to the nearest whole number gives the answer:

ΔHrxn = -59 kJ/mol AgCl (Choice C)

Two Solutions,initially at 24