Final answer:
The energy obtained from burning 1 kg of coal, given a heat of combustion of 30 MJ/kg, is 30,000,000 J (30 MJ).
Step-by-step explanation:
To calculate the amount of energy obtained from burning 1 kg of coal, we use the heat of combustion of coal, which is the amount of energy released when a certain amount of substance is burned. The heat of combustion for coal is typically around 30 MJ/kg. Therefore, the energy obtained from burning 1 kg of coal is:
Energy = (Mass of coal) × (Heat of combustion)
Energy = (1 kg) × (30 MJ/kg)
Energy = 30 MJ
To convert megajoules (MJ) into joules (J), since 1 MJ is equal to 1,000,000 J (10⁶ J), the energy in joules is:
Energy = 30 × 10⁶ J
Energy = 30,000,000 J