First let us calculate for the rate constant k from the
formula:
k = ln(2) / t0.5
where t0.5 is the half life
k = ln(2) / 1.3x10^9 years
k = 5.33x10^-10 years-1
Then we use the formula:
A/Ao = e^-kt
where A/Ao is the amount remaining = 25% = 0.25, t is
time
Rearranging to get t:
t = ln(A/Ao) / -k
t = ln(0.25) / (-5.33x10^-10 years-1)
t = 2.6x10^9 years
The oxidation state of a substance is the electric charge it is exhibiting in a given state. This may be determined by looking at the oxidation states of accompanying atoms as well as the charge on the complete molecule.
In this case:
Molecular charge: 0
Oxidation state of oxygen: -2 (it is a group 6 element)
Thus,
S + 3 * -2 = 0
S = 6
Sulfur is exhibiting an oxidation state of +6.
Answer:
C. 6.99 moles
Explanation:
To convert molecules to moles we simply divide the given number of molecules by Avogadro's number, 6.022 x 10²³
Given number of molecules : 4.21 x 10^24
Number of moles : 4.21 x 10^24 / 6.022 x 10²³ = 6.99 moles ( rounded )
The answer is C
