Question

A calorimeter contains 20.0 mL of water at 15.0 ∘C . When 1.50 g of X (a substance with a molar mass of 76.0 g/mol ) is added, it dissolves via the reaction X(s)+H2O(l)→X(aq) and the temperature of the solution increases to 25.0 ∘C . Calculate the enthalpy change, ΔH, for this reaction per mole of X. Assume that the specific heat of the resulting solution is equal to that of water [4.18 J/(g⋅∘C)], that density of water is 1.00 g/mL, and that no heat is lost to the calorimeter itself, nor to the surroundings.

Answer 1

Answer:

ΔH(mix'g)= 42.3Kj/mole

Explanation:

ΔH = (mcΔT)water/moles X

m = mass(g) = 20ml x 1.00g/ml = 20 g

c = 4.184 j/g⁰C

ΔT = 25°C- 15°C = 10°C

moles X = (1.5g)/(76g/mole) = 0.0197 mole X

ΔH = (20g)(4.184j/g°C)(10°C)/(0.0197 mole X) = 42,300J/mole = 42.3Kj/mole (3 sig.figs.)