C. because it produce heat..
Because 25% is half of 0.5 and the half life of is given as 5,715, the time it takes to reach this amount should just be double the half life: 11430 years.
However, in other cases the problem may not have easy numbers, so below is a more mathematical approach.
The half life formula is .
Solving for t gives:
Given information:
Plug in given values and solve for t.
With correct significant figures, this would be 11000 years.
Explanation:
Molar mass of is 114.23 g/mol. Therefore, its number of moles are calculated as follows.
No. of moles =
=
= 0.043 mol
So, 0.043 moles are releasing 239.5 kcal of heat. Hence, heat released by 1.54 mol will be calculated as follows.
= 8577.44 kcal
Thus, we can conclude that 8577.44 kcal heat is released by the combustion of 1.54 mol of .
Answer:
1. use a ruler to measure how many heights the ball falls down.
2. use notes to record observations.