Question

The following data refers to an aluminium rod, 200 cm in length, being heated by burning coal:
Initial temperature of the rod-------25`C 🌡️
Amount of coal burned-------750g
Percentage of heat transferred to the rod-----60%
Mass of the rod------10 000g

Calculate:
(E)The quantity of heat transferred to the rod

Answer 1

To calculate the quantity of heat transferred to the rod, we can use the formula:

\[
Q = \text{Mass of coal burned} \times \text{Heat value of coal} \times \text{Percentage of heat transferred}
\]

However, we need the heat value of the coal to conduct this calculation. The heat value can vary depending on the type of coal, but a common approximate value for sub-bituminous coal is about 24 MJ/kg.

First, let's convert the mass of coal burned from grams to kilograms:

\[
\text{Mass of coal burned} = 750 \, \text{g} = 0.750 \, \text{kg}
\]

Now, we can calculate the total heat produced by the burned coal:

\[
Q_{\text{total}} = \text{Mass of coal burned} \times \text{Heat value of coal}
\]
\[
Q_{\text{total}} = 0.750 \, \text{kg} \times 24 \, \text{MJ/kg} = 18 \, \text{MJ} = 18,000 \, \text{kJ}
\]

Now, we need to calculate the quantity of heat that is transferred to the rod, taking into account the 60% efficiency:

\[
Q_{\text{transferred}} = Q_{\text{total}} \times \text{Percentage of heat transferred}
\]
\[
Q_{\text{transferred}} = 18,000 \, \text{kJ} \times 0.60 = 10,800 \, \text{kJ}
\]

Thus, the quantity of heat transferred to the rod is **10,800 kJ**.