Hey there!
A half-life means after a certain amount of time, half of that substance will have decayed after that time.
An equation for exponential decay is the following:
y = a(1 - b)ⁿ
Where a is the original amount, b is the rate of decay, and n is time.
1000 is about 0.3 of a half life, 1000 divided by 138 days (3312 hours) is approximately 0.3.
Let's plug in values to that equation:
y = 321(1 - 0.5)^(0.3)
Simplify.
y = 260.73
There will be 260.73mg of polonium-210 remaining after 1000 hours.
Hope this helps!
Answer:
A. 29.9
Explanation:
- An element can have differing numbers of neutrons in its nucleus, but it always has the same number of protons. The versions of an element with different neutrons have different masses and are called isotopes.
- The average atomic mass for an element is calculated by summing the masses of the element’s isotopes, each multiplied by its natural abundance on Earth.
<em>Average atomic mass of P = ∑(Isotope mass)(its abundance)</em>
∴ Average atomic mass of P = (P-29 mass)(its abundance) + (P-30 mass)(its abundance) + (P-31 mass)(its abundance) + (P-33 mass)(its abundance)
<em>Abundance of isotope = % of the isotope / 100.</em>
<em>∴ Average atomic mass of P =</em> (29)(0.327) + (30)(0.4803) + (31)(0.184) + (33)(0.0087) = <em>29.88 a.m.u ≅ 29.9 a.m.u.</em>
<em></em>
<em>So, the right choice is: A. 29.9</em>
Answer:
The color black absorbs most colors, while white reflects most colors.
Answer:
The force applied to the object is an external force, from outside the system. When it does positive work it increases the gravitational potential energy of the system. Because gravitational potential energy depends on relative position, we need a reference level at which to set the potential energy equal to 0.