Equation for Half life :
A = a(0.5)^(t/h)
A is current amount, "a" is initial amount, h is halflife, t is time
5 = 40(0.5)^(t/1.3x10^9)
5/40 = (0.5)^(t/1.3x10^9)
take the log of both sides , power rule
Log(5/40) = (t/1.3x10^9) * Log(0.5)
(1.3x10^9) * Log(5/40) / Log(0.5) = t
3.9x10^9 years = t
And if you think about what a half life is, the time it take for the amount to reduce to half.
40/2 = 20
20/2 = 10
10/2 = 5
It went through 3 half-lifes
3 * 1.3x10^9 = 3.9x10^9 years
Answer:
There is NO cure for Down Syndrome
Explanation:
Down syndrome cannot be cured. Early treatment programs can help improve skills. They may include speech, physical, occupational, and/or educational therapy. With support and treatment, many people with Down syndrome live happy, productive lives
Atomic radio increases as number of valence electrons increase. Hence the first and fourth statement are wrong. Electronegativity is highest for elements on the TOP right hand corner of the periodic table so the third statement is wrong. Hence the answer is the third statement
Answer and Explanation:
The primitive atmosphere of Earth may have favored the abiotic synthesis of organic molecules because it **had close to no oxygen, hence, it was powerfully reducing. It had pure energy sources too in form of ultraviolet rays from the sun (it was extremely hot! Too hot for water in liquid form to exist in fact!), outgassing from the numerous volcanoes and lightning**.
Abiotic synthesis means a formation reaction where the reactants are charged to become products, almost all on their own, with no catalyst especially.
So, these factors would have helped the organic molecules to form as most of what is needed to overcome the energy barrier and become products.
Answer:
NaZ + H2O <----> HZ + OH-
[OH-] = [HZ]
[NaZ] = 0.15 M
pH = 10.7, so the pOH = 14-10.7 = 3.3; [OH-] = 10^-3.3 = 5.01E-4
kb = [OH-][HZ]/[NaZ] = (5.01E-4)^2/0.15 = 1.67E-6
ka = kw/kb = 1E-14/1.67E-6 = 5.99E-9 = 6.0E-9
