Answer:
1306.67 s
Step-by-step explanation:
From the question given above, the following data were obtained:
Volume of water = 70 L
Power (W) = 18000 w
Specific heat capacity (C) = 4200 J/g℃
Initial temperature (T1) = 20 ℃
Final temperature (T2) = 100 ℃
Time (t) =?
Next, we shall determine the mass of the water. This can be obtained by converting 70 L to kg. This is illustrated below:
1 L = 1 kg
Therefore,
70 L = 70 Kg
Thus, the mass of the water is 70 kg.
Next, we shall determine the heat energy involved. This is can be obtained as follow:
Mass (M) of water = 70 Kg
Specific heat capacity (C) = 4200 J/g℃
Initial temperature (T1) = 20 ℃
Final temperature (T2) = 100 ℃
Heat Energy (Q) =?
Q = MC(T2 – T1)
Q = 70 × 4200 × (100 – 20)
Q = 294000 × 80
Q = 3520000 J
Thus, the heat energy involved is 3520000 J
Finally, we shall determine the time taken.
Power (W) = 18000 w
Heat Energy (Q) = 3520000 J
Time (t) =?
Power = energy / time
18000 = 3520000 / time
Cross multiply
18000 × time = 3520000
Divide both side by 18000
Time = 3520000 / 18000
Time = 1306.67 s