Answer:
139.98 g to nearest hundredth.
Explanation:
Using Avogadro's Number:
One mole (167.26 g) of Erbium equates to 6.022141 * 10^23 atoms.
So 5.04 * 10^23 = 167.26 * 5.04/6.022141
= 139,98 g.
I would say the energy has to be decreased by 87 kj because the bonding is held together by 87 kj so removing that should prevent the bonding from taking place or reverse it I believe. In other words, a certain amount of energy is required to hold the bond together and in the absence of that energy, the bonding will not take place.
The mass of 165.0 g sample that remains after 90.0 minutes is 5.16 grams
calculation
lambda㏑2/18= 0.0385
m(t)= 165 x e( 0.0385 x90) =5.16g
