To make sure no cracks are in the crucible and also to remove any moisture present in the crucible by the process of heating.
C
Everyday, ever hour and so on the weather changes, when looking at the weather on an app or website, the weather is defined by the conditions at a certain time. Hope this helps!
Molar mass=MM
MM(Hg)=200.59g/mol
MM(N)=14.01g/mol
MM(O)=16.00g/mol
MM(Hg(NO3)2)=MM(Hg)+2*MM(N)+6*MM(O)=200.59g+2*14.01g+6*16g=324.61g/mol
1.60mol Hg(NO3)2*(324.61g/mol)=519.376 g=519 g Hg(NO3)2