Chemistry: CaO(s) + H2O(l) - Ca(OH)2(s) enthalpy of rxn= -63.7 kJ/molrxn Calcium oxide, CaO(s), has been proposed as a substance that can be used to heat water quickly for portable heating packs or for cooking. When placed in water, Cao(s) reacts as shown by the equation above. A student wants to design a heating pad that could heat a 150.0 g sample of water from 25.0°C to 60.0°C. Calculate the amount of heat, in joules, that the water must absorb for its temperature to change by this amount. (Assume that

CaO(s) + H2O(l) - Ca(OH)2(s) enthalpy of rxn= -63.7

Ответ:

21gl13826

25.01.2022

21,976 J

Explanation:

In order to increase the temperature of a certain amount of a substance by $\Delta T$ , the amount of heat that must be supplied to the substance must be:

$Q=mC\Delta T$

where

m is the mass of the substance

C is the specific heat capacity of the substance

$\Delta T$ is the increase in temperature

For the sample of water in this problem we have:

m=150.0 g is the mass

$C=4.186 J/g^{\circ}C$ is the specific heat capacity of water

$\Delta T=60.0-25.0=35.0^{\circ}C$ is the increase in temperature

Therefore, the amount of heat that must be supplied is

Q=(150.0)(4.186)(60-0-25.0)=21,976 J

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