Latent heat

How much heat is needed to take from 100 g of water at 20°C to cool to ice at -18°C? Mass heat capacity c (ice) = 21kJ/kg / °C; c (water) = 4.19 KJ/kg / °C and the mass group heat of solidification of water is l = 334kJ/kg

Correct answer:

Q =  45.56 kJ

Step-by-step explanation:

m=100 g kg=100/1000  kg=0.1 kg t1=20 °C t2=0 °C t3=18 °C  c1=2.1 kJ/kg/°C c2=4.19 kJ/kg/°C l=334 kJ/kg  Q1=m c2 (t1t2)=0.1 4.19 (200)=41950=8.38 kJ Q2=m l=0.1 334=1675=33.4 kJ Q3=m c1 (t2t3)=0.1 2.1 (0(18))=18950=3.78 kJ  Q=Q1+Q2+Q3=8.38+33.4+3.78=45.56 kJ



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