Answer:
83 .
Explanation:
Radioactive elements: It is defined as the atoms which contains unstable nucleus because of the constantly change and imbalance of energy in the nucleus. Radioactivity of an atom is showing by when the nucleus of an atom loose a neutron, it gives an energy and this process is called to be radioactivity.
Isotopes elements containing different number of neutrons and same number of protons. All isotopes are not considered as radioisotopes. All isotopes of an element with an atomic number greater than 83 are radioactive means, they are having unstable nucleus.
Answer:
it will take 444.44 min to reach 0.25 M from 0.75 M
Explanation:
since the reaction constant is k= 6.00*10⁻³ L*mol⁻¹min⁻¹. For a reaction rate of the form
-dCa/dt=k*Caⁿ
doing a dimensional analysis
[dCa/dt]= mol/(L*min) = [k]*[Caⁿ] = L/(mol*min) * (mol/L)ⁿ
then only n=2 can comply with the dimensional analysis, therefore we get a the second order reaction . Thus
-dCa/dt=k*Ca²
-dCa/Ca² =k*dt
-∫dCa/Ca² =k*∫dt
(1/Ca₂ - 1/Ca₁)= k*Δt
Δt= 1/k*(1/Ca₂ - 1/Ca₁)
replacing values
Δt= 1/k*(1/Ca₂ - 1/Ca₁) = 1/(6.00*10⁻³ L*mol⁻¹min⁻¹)*(1/0.25 M - 1/0.75 M)= 444.44 min
Answer:
Chemical science arises in the seventeenth century from the studies of alchemy popular among many of the scientists of the time. The basic principles of chemistry are considered to be collected for the first time in the work of the British scientist Robert Boyle: The Skeptical Chemist (1661).
Emest Rutherford proved that the plum pudding model was incorrect then he experimented by firing cathode rays at gold foil.
