In this solution we will need two steps, 1) calculate the heat required to get water to the temp of 100 C and 2) find the latent heat of vapourization required.
First, change the 11.8g to kg: = 0.0118kg Equations: Q = mcT, Q=mL
c for water = 4186 J/(kg C) L for water = 22.6 x 10^5 J/kg
1) Q = mcT Q = 0.0118 kg x 4186 J/(kg C) x (100 C - 65.5 C) Q = 1704.12 J
The pendulum would stop swinging because the kinetic energy would slow down for the friction is causing it to slow. The energy would go into potential energy.
The answer is Strontium(Sr). The reactive increase from right to left. And this element has two valence electrons. So Rb is not correct. Then the very reactive metal is Sr.