I believe the answer to this question is true
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
Electron capture occurs when one of the electrons in the atom is captured by the atom's nucleus. The captured electron combines with one proton to form a neutron.
We have to find the nuclide that is produced when the aluminum-28 undergoes an electron capture.
If we look for the atomic number of Al in the periodic table we will see that it is 13. That means that it has 13 protons. Then we are given the atomic mass of aluminum, it is 28. That means that if we add the number of protons and the number of neutrons we get 28.
atomic mass = n° of protons + n° of neutrons = 13 + 15 = 28
atomic number = n° of protons = 13
The nucleus of the aluminum atom will capture one electron that will combine with a proton of the nucleus to form a neutron. So the atomic number will change because it will have 1 proton less. But the atomic mass won't change because we are losing one proton but winning a neutron, so it remains the same. After the electron capture, the new nuclide will have:
atomic mass nuclide = n° of protons + n° of neutrons = 12 + 16 = 28
atomic number nuclide = n° of protons = 12
If we look for the element that has an atomic number of 12 in the periodic table we will see that it is magnesium.
Finally we can express this like a reaction:
28 0 28
Al + e --------> Mg
13 -1 12
Answer:
28
Mg
12
<u>Answer: </u>The correct answer is Silver.
<u>Explanation:</u>
Specific heat of fusion is defined as the amount of heat which is required to raise the temperature of 1 gram of a substance to 1°C. It is generally expressed in kJ/mol
We are required to find the substance which require more heat. For that we need to know the specific heat of all the substances.
The substance which have the highest specific heat, will require more heat.
The specific heat of the given substances are:
Silver = 11.3 kJ/mol
Sulfur = 1.7175 kJ/mol
Water = 5.98 kJ/mol
Lead = 4.799 kJ/mol
The specific heat of silver is the highest and hence, will require more heat.
Hence, the correct answer is silver.