please help me!
you don’t have to answer all but I’d appreciate it

1) Given that H(g) + H(g) H2(g) ∆H°= -436.4 kJ/mol Calculate the change in mass (in kg) per mole of H2 formed.


2) The radius of a uranium-235 nucleus is about 7.0 10-3 pm. Calculate the density of the nucleus in g/cm3. (Assume the atomic mass in 235 amu.)


3) Write balanced nuclear equations for the following reactions and identify X:
(a) X(p,α)12 6 C
(b) 27 13 Al(d,α)X
(c) 55 25 Mn(n,)X


4) Strontium-90 is one of the products of the fission of uranium-235. This strontium isotope is radioactive, with a half-life of 28.1 yr. Calculate how long it will take for 0.900 g of the isotope to be reduced to 0.170 g by decay.