Freezing can supply the missing warming energy

Mix 0.150 kg ice at −20°C with 0.100 kg water at 0°C under the ideal equilibrium model. Use ci = 2100 J/(kg·K), cw = 4200 J/(kg·K), and Lf = 334000 J/kg.

How much of the initial water freezes?

Organize the givens & assumptions

Ice = 0.150 kg at −20°C
Water = 0.100 kg at 0°C
ci = 2100 J/(kg·K)
Lf = 334000 J/kg

Ideal insulated calorimetry at ordinary atmospheric pressure, no evaporation or other work, equilibrium final state and stated constant model capacities unless a temperature dependence is specified. Vessel heat capacity is negligible except where it is an explicit unknown. Pure ice/water melts at 0°C; no supercooling.

A $0$
B $100\ \mathrm g$
C $37.72\ \mathrm g$
D $18.86\ \mathrm g$

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