Answer : Normally in any chemical reaction, if the enthalpy change i.e. ΔH is positive which means it is greater than zero then it can be called as an Endothermic Reaction.
Whereas, the system under study is absorbing heat that is produced during the reaction. So if ΔH is found to be positive then it can be called as endothermic reaction.
The change in internal energy of the combustion of biphenyl in Kj is calculated as follows
=heat capacity of bomb calorimeter x delta T where delta T is change in temperature
delta T = 29.4 -25.8= 3.6 c
= 5.86 kj/c x 3.6 c = 21.096 kj
Chemical change or process
Ur answer is going to be francium
Characteristics of a medium wave. They are <span>Wavelengths in this band are long enough that radio waves are not blocked by buildings and hills and can propagate beyond the horizon following the curvature of the Earth; this is called the </span>ground wave<span>. Practical groundwave reception typically extends to 200–300 miles, with longer distances over terrain with higher </span>ground conductivity<span>, and greatest distances over salt water. Most broadcast stations use ground wave to cover their listening area. Hope this helps. :)</span>
