Question

What mass of butane, C 4 H 10 , is required to heat 0.35 gallon of H 2 O from 22°C to 100°C?
Density of H 2 O = 1.00 g/mL; specific heat capacity of H 2 O = 4.184 J/g°C;
ΔH° of combustion of C 4 H 10 = –126 kJ/mol; 1 gal = 4 qt; 1 qt = 946.4 mL

Answer 1

volume of H2O = 0.35 gal

                         = 1324.96 mL

mass of water = 1324.96 g

specific heat = 4.184 J / g oC

temperature rise = 100 - 22 = 78 oC

Q = m Cp dT

   = 1324.96 x 4.184 x 78

Q = 432403.3 J

Q = 432.4 kJ

ΔH° = - 126 kJ/mol

ΔH° = - Q / n

- 126 = - 432.4 / n

n = 3.43

moles of butane = 3.43 mol

mass of butane = 199 g