Adenine is added to the sequence
Given the length of each side of a cube and its mass, the density can be obtained which can then help identify the type of material it's made of. This is because density is a unique and intrinsic property of materials. For this problem, the density is determined to be 10g/cm^3. Looking at a table of densities, the metal is most likely actinium, which has an exact density of 10 g/cm^3.
(1) A,B,C is your answer, a decreasing pH means there is a higher H+ concentration
In chemical equilibrium, radioactive decay occurs because of unstability due to the high neutron-to-proton ratio. Through time, the radioactive element is converted to a new element. This radioactive decay undergoes first order reaction. Its equation is in the form of
A = A₀e^(-kt), where A is the amount of the element after time t, A₀ is the original amount of element at t=0 and k is the rate constant.
Half-life is the amount of time for A to be 1/2 of A₀. Modifying the equation during half time, we let A=1/2 A₀. Then.
1/2 A₀ = A₀e^(-kt)
1/2 = e^(-k(5730))
k = 0.000121
Thus, the first-order rate constant is equal to 0.000121 per year.