Answer to Question #144592 in General Chemistry for Hilma

Question

1.Isooctane burns in air to give water and carbon dioxide (drHO=-109992 KJ/mol- rxn). What is the enthalpy change if you burn 1.00L of Isooctane?

2. The freezing point of mercury is -38.8 degrees Celsius. What quantity of energy in joules is released to the surroundings if 1.00 mL of mercury is cooled from 23.0 to -38.8 degrees celsius?

Answer 1

1.) Density of isooctane= 0.69g/mL

Mass = 0.69g/mL ×1000mL = 690g

Equation : 2C₈H₁₈ + 25O₂ = 16CO₂ + 18H₂O

2[(12×8)+ 18]g C₂H₁₈ = -109992KJ/mol

228 g C₂H₁₈= -109992KJ/mol

1 g C₂H₁₈ = -109992KJ/mol / 228g

690g C₂H₁₈ = -109992/228 × 690

= -332871 KJ/mol

2) specific heat capacity of mercury = 0.14J/g.K

Density of mercury = 5.43g/mL

Mass = 5.43g/mL ×1mL = 5.43g

H=mcΔt = 5.43 × 0.14 × (-38.8-23) = 5.43 ×0.14× -61.8

= -46.98 J