To find out how many joules of energy the chocolate bar contains, you can use the conversion factor provided (1 kg = 100 j).
The chocolate bar weighs 1.2 kg.
To calculate the energy in joules:
\[ \text{Energy (j)} = \text{Mass (kg)} \times \text{Energy per kg (j/kg)} \]
Substituting the values:
\[ \text{Energy (j)} = 1.2 , \text{kg} \times 100 , \text{j/kg} \]
\[ \text{Energy (j)} = 1.2 \times 100 = 120 , \text{j} \]
Therefore, the chocolate bar contains 120 joules of energy.