Answer:
A.55.49W, B. 25g
Explanation:
The heat required to free the water at 17°c is that required to reduce it to water at 0°c plus that to convert it to ice at 0°c plus that required to get it to ice at -12°c.
Note that in the conversion process mass is constant.
Hence the heat extracted is defined as mass ×specific heat capacity × temperature change.
But on conversion from water to ice at 0°c the heat extracted is mass × latent heat of fusion.
Putting all together we have :
26 ×4.186 ×(0-19) -26 ×334 + 26 × 2.090× (-12-0)
=2067.884+8684+652.08=9988.16J
This is the output power
From performance formula;
Coefficient of performance=output power /input power
Input power = output power / coefficient of performance
Input power=9988.16J/3 =3329.39j
In watt we divide by 60
3329.39/60= 55.49W
Note the negative sign is just an indication that heat is been lost from the system.
B. Let's calculate Energy per unit mass of the process
9988.16J/26 =384.16J/g
Power consumption is 160w
This is the input power of the system
160 W is available to make ice.
This means 160 ×60 J is the energy available to make ice since the whole process takes 60s.
That energy =9600J
But the output energy per unit mass is 384.16J/g.
Hence the required mass for 9600J is
9600/384.16= 24.99g
Approximately 25g
