Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.

            Q  =  3.06 kJ

Solution:

The equation used for this problem is as follow,

                                                 Q  =  m Cp ΔT   (1)

Where;

           Q  =  Heat  =  ?

           m  =  mass  =  125 g

           Cp  =  Specific Heat Capacity  =  0.450 J.g⁻¹.°C⁻¹

           ΔT  =  Change in Temperature  =  78.0 °C - 23.5 °C  =  54.5 °C

Putting values in eq. 1,

                            Q  =  125 g × 0.450 J.g⁻¹.°C⁻¹ ×  54.5 °C

                            Q  =  3065 J

Or,

                            Q  =  3.06 kJ

vanderwaal's forces of attraction are the electrostatic intermolecular forces that exist in a molecule due to the temporary or permanent dipoles that are developed in a molecule. in , the major intermolecular forces are dipole-dipole interactions as the molecule is polar (bent structure). so the vanderwaal's forces of interaction in between molecules are the permanent dipole-dipole interactions that develop due to the dipole that exists in between the polar h - s bond. the positively charged hydrogen atom is attracted towards the negative end of the dipole that is sulfur of the adjacent molecule. therefore, these forces of attraction are relatively stronger than that of london dispersion forces that exist in non polar molecules.

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