The enthalpy of combustion of hard coal averages -35 kj/g, that of gasoline, 1.28 x 105 kj/gal. how many kilograms of hard coal provide the same amount of hat as is available from 1.0 gallon gasoline? assume that the density of gasoline is 0.692 g/ml(the same s density of isooctane).

3.657 kg

Explanation:

Given:

Enthalpy of combustion of hard coal = -35 kJ/g

Enthalpy of combustion of gasoline = 1.28 × 10⁵ kJ/gal

Density of gasoline = 0.692 g/mL

now,

The heat provide 1 gallon of gasoline provide =  1.28 × 10⁵ kJ

and,

heat provided by the 1 gram of coal  = 35 kJ

or

1 kJ of heat is provided by (1/35) gram of hard coal

therefore,

For 1.28 × 10⁵ kJ of heat, mass of hard coal =  1.28 × 10⁵ kJ × (1 / 35)

or

For 1.28 × 10⁵ kJ of heat, mass of hard coal = 3657.14 grams = 3.657 kg

weight of any object is given by

w = m*g

where m is mass of the object and g is the acceleration due to gravity.

for earth the value of g is 9.8 m/s^2 so

w=117.6 n m=12 g=?

117.6=12g => g=9.8 m/s^2

which is the force of gravity on earth.