Question

In a coffe cup calorimeter, 50.0mL of 0.100M of AgNO3 and 50mL of 0.100M HCl are mixed to yield the following reaction:

Ag+ (aq) + Cl -==> AgCl(s)

The two solutions were initially at 22.60°C, and the final temperature is 23.40°C. How do I calculate the heat that accompanies this reaction in kJ/mol, assuming that the combined solution has a mass of 100g and a specific heat capacity of 4.18 J/g°C.

Answer 1

The enthalpy change of the reaction is -66.88 kJ/mol.

Step-by-step explanation:

Mass of the solution = m = 100 g

Heat capacity of the solution = c = 4.18 J/g°C

Initial temperature of the solutions before mixing =
`T_1=22.60^oC`

Final temperature of the solution after mixing =
`T_2=23.40^oC`

Heat gained by the solution due to heat released by reaction between HCl and silver nitrate = Q

`Q=m* c* (T_2-T_1)`

`Q=100 g* 4.18 J/g^oC* (23.40^oC-22.60^oC)=334.4 J`

Heat released due to reaction = Q' =-Q = -334.4 J

Moles of silver nitrate = n

Molarity of silver nitrate solution = 0.100 M

Volume of the silver nitrate solution = 50.0 mL = 0.050 L ( 1 mL = 0.001 L)

`Moles =Molarity* Volume (L)`

`n=0.100 M* 0.050 L=0.005 mol`

Enthalpy change of the reaction =
`\Delta H`

`=\Delta H=(-334.4 J)/(0.005 mol)=-66,880 J/mol=-66.88 kJ/mol`

1 J = 0.001 kJ

The enthalpy change of the reaction is -66.88 kJ/mol.