Answer:
after 45 days 9 g left
Explanation:
Given data:
Half life Na-24 = 15 days
Mass of sample = 72 g
Mass remain after 45 days = ?
Solution:
Number of half lives passed:
Number of half lives = time elapsed / half life
Number of half lives = 45 days / 15 days
Number of half lives = 3
At time zero total amount = 72 g
After first half life = 72 g/ 2= 36 g
At 2nd half life = 36 g/2 = 18 g
At 3rd half life = 18 g/2 = 9 g
Thus after 45 days 9 g left.
Where are the equations ..
Sorry....
Planets move slower when they are furthest from the sun. But when they are closer they move faster because of the gravitational pull of the Sun.
Hope this helps.
Can you attach the following concept map on chemical reactions?
It is A. This is because the rate of reaction is defined as the speed at which the reactants are converted into the products.
