Nickel-63 is a radioactive element that decays to copper-63. Nickel-63 has a half-life of approximately 100 years. Vincent predicts that about 50 grams of a 200-gram sample of nickel-63 remains after 200 years. Is he correct? Why or why not? Explain.

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

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms

Abeaker with 2.00×102 ml of an acetic acid buffer with a ph of 5.000 is sitting on a benchtop. the total molarity of acid and conjugate base in this buffer is 0.100 m. a student adds 4.70 ml of a 0.360 m hcl solution to the beaker. how much will the ph change? the pka of acetic acid is 4.740.