Answer:
7628 y
Explanation:
Carbon-14 is radioactive and it follows the first-order kinetics for a radioactive decay. The first-order kinetics may be described by the following integrated rate law:
![ln(\frac{[A]_t}{[A]_o})=-kt](https://tex.z-dn.net/?f=ln%28%5Cfrac%7B%5BA%5D_t%7D%7B%5BA%5D_o%7D%29%3D-kt)
Here:
![[A]_t](https://tex.z-dn.net/?f=%5BA%5D_t)
is the mass, moles, molarity or percentage of the material left at some time of interest t;
![[A]_o](https://tex.z-dn.net/?f=%5BA%5D_o)
is the mass, moles, molarity or percentage of the material initially, we know that initially we expect to have 100 % of carbon-14 before it starts to decay;
is the rate constant;
is time.
The equation becomes:
![ln(\frac{[A]_t}{[A]_o})=-\frac{ln(2)}{T_{\frac{1}{2}}}t](https://tex.z-dn.net/?f=ln%28%5Cfrac%7B%5BA%5D_t%7D%7B%5BA%5D_o%7D%29%3D-%5Cfrac%7Bln%282%29%7D%7BT_%7B%5Cfrac%7B1%7D%7B2%7D%7D%7Dt)
Given:
![\frac{[A]_t}{[A]_o} = \frac{40.0 %}{100.0 %}](https://tex.z-dn.net/?f=%5Cfrac%7B%5BA%5D_t%7D%7B%5BA%5D_o%7D%20%3D%20%5Cfrac%7B40.0%20%25%7D%7B100.0%20%25%7D)
Solve for time:
![t = -\frac{ln(\frac{[A]_t}{[A]_o})\cdot T_{\frac{1}{2}}}{ln(2)}](https://tex.z-dn.net/?f=t%20%3D%20-%5Cfrac%7Bln%28%5Cfrac%7B%5BA%5D_t%7D%7B%5BA%5D_o%7D%29%5Ccdot%20T_%7B%5Cfrac%7B1%7D%7B2%7D%7D%7D%7Bln%282%29%7D)
In this case:
Answer:
0.13 g
Explanation:
mass of aluminum required = ( Dislocation length) / ( Dislocation density) × (density of metal)
3000 miles to cm ( 1 mile = 160934 cm) = 3000 miles × 160934 cm / 1 mile = 482802000 cm
density of Aluminium = 2.7 g /cm³
dislocation density of aluminum = 10¹⁰ cm³
mass of aluminum required = (482802000 cm × 2.7 g/cm³) / 10¹⁰ cm³ = 0.13 g
Air is a mixture because it is made up of many constituents like oxygen, argon etc. it can be physically separated by fractional distillation. it doesnt have a formula unlike compounds and elements. its composition varies differently with its constituents.
