Question 3: How many atoms are in 25.00 g of B.
A. 1.393 x 10^24 atoms of B
B. 1.333 x 10^23 atoms of B
C. 2.16 x 10^26 atoms of B
D.217 x 10^24 atoms of B
Question 4:
How many grams is 2.393 x 10^24 atoms of O
A. 70.45 g O
B. 140.9 g O
C. 63.58 mole O
D. 63.58 g O
Please answer both questions if you can, thanks for all the efforts :)

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.

Structure of the atoms: discovery of the nucleus in 1909i need answering all of these questions

Areaction is first order. if the initial reactant concentration is 0.0200 m, and 25.0 days later the concentration is 6.25 x 10-4 m, then its half-life is: