Amount of Niobium-91 initially
= 300/91 =3.2967mol
2040 years = 3 ×680 = 3 half-lives
therefore, amount left = 0.4121mol
mass of Niobium-91 remaining = 0.4121 ×91 =37.5g
Answer:
unsafe, solar
Explanation:
A lunar eclipse covers the moon which is safe to look at. New Moon, again is simply the moon. However, we should never look at the sun, eclipsed or not!
Answer:
Explanation:
2Al + 3Cl2 --> 2AlCl3
Ag2O + Be -----> 2Ag + BeO
4K + O2 ---> 2K2O
CoP + 3NaBr ---> CoBr3 + Na3P
Si + Hg2S ---> SiS2 + Hg
6Li + Ni3N2 --- > 2Li3N + 3Ni
3Ca + 2K3N --> Ca3N2 + 6K
SnS2 + 2F2 --> SnF4 + 2S