How many moles is there in 59.6g of BaSO4 with work please

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.

Acontrol during an experiment. might change remains constant does not exist does change