Heat is added to 110.0 grams of liquid of water at 50.00°C to produce water vapor. The vapor is collected and heated to a temperature of 110.0°C. How many joules of heat energy were required in total for this process?

Respuesta :

Answer : The heat energy required in total for this process was 273529.7 joules.

Solution :

The conversions involved in this process are :

[tex](1):H_2O(l)(50^oC)\rightarrow H_2O(l)(100^oC)\\\\(2):H_2O(l)(100^oC)\rightarrow H_2O(g)(100^oC)\\\\(3):H_2O(g)(100^oC)\rightarrow H_2O(g)(110^oC)[/tex]

Now we have to calculate the enthalpy change.

[tex]\Delta H=[m\times c_{p,l}\times (T_{final}-T_{initial})]+n\times \Delta H_{vap}+[m\times c_{p,g}\times (T_{final}-T_{initial})][/tex]

where,

[tex]\Delta H[/tex] = enthalpy change or heat required = ?

m = mass of water = 110.0 g

[tex]c_{p,l}[/tex] = specific heat of liquid water = [tex]4.18J/g^oC[/tex]

[tex]c_{p,g}[/tex] = specific heat of water vapor = [tex]1.84J/g^oC[/tex]

n = number of moles of water = [tex]\frac{\text{Mass of water}}{\text{Molar mass of water}}=\frac{110.0g}{18g/mole}=6.11mole[/tex]

[tex]\Delta H_{vap}[/tex] = enthalpy change for vaporization = 40.67 KJ/mole = 40670 J/mole

Now put all the given values in the above expression, we get

[tex]\Delta H=[110.0g\times 4.184J/gK\times (100-50)^oC]+6.11mole\times 40670J/mole+[110.0g\times 1.84J/gK\times (110-100)^oC][/tex]

[tex]\Delta H=273529.7J[/tex]

Therefore, the heat energy required in total for this process was 273529.7 joules.