In a constant‑pressure calorimeter, 60.0 mL of 0.300 M Ba (OH) 2 was added to 60.0 mL of 0.600 M HCl. The reaction caused the temperature of the solution to rise from 22.74 ∘ C to 26.83 ∘ C. If the solution has the same density and specific heat as water, what is heat absorbed by the solution?

Q sln = 75.165 J

Explanation:

a constant pressure calorimeter:

Q sln = mCΔT

∴ m sln = m Ba (OH) 2 + m HCl

∴ molar mass Ba (OH) 2 = 171.34 g/mol

∴ mol Ba (OH) 2 = (0.06 L) (0.3 mol/L) = 0.018 mol

⇒ mass Ba (OH) 2 = (0.018 mol) (171.34 g/mol) = 3.084 g

∴ molar mass HCl = 36.46 g/mol

∴ mol HCl = (0.06 L) (0.60 mol/L) = 0.036 mol

⇒ mass HCl = (0.036 mol) (36.46 g/mol) = 1.313 g

⇒ m sln = 3.084 g + 1.313 g = 4.3966 g

specific heat (C):

∴ C sln = C H2O = 4.18 J/g°C

∴ ΔT = 26.83°C - 22.74°C = 4.09°C

heat absorbed (Q):

⇒ Q sln = (4.3966 g) (4.18 J/g°C) (4.09°C)

⇒ Q sln = 75.165 J