Answer:
All these theories can be grouped into the following two general classes. Formation of the solar system quickly and violently: Old planetesimal hypotheses, Nebular hypotheses, new planetesimal hypotheses and tidal hypotheses are some examples of it.
Explanation:
To make sure that an equation is balanced, we need to have the same number of atoms on both sides. If we had only 2(I₄O₉) on one side, then the other side would need to have 8 iodine atoms and 18 oxygen atoms to obey the law of conservation of mass. This can be found by multiplying the coefficient to the subscript followed by the element symbol.
Your correct answer is 8 iodine atoms and 18 oxygen atoms.
Answer:
First balance the equation
C2H6 + 7/2O2 2CO2 +3H2O
for one mole of C2H6 there are 7/2 mole of O2 required. so for4.50 moles you require 4.50 x 7/2 = 15.75 moles of O2.
This is a relatively easy half-life problem.
Whenever a half-life has expired, one half of the radioactive isotope will no longer be present.
When 2 half-lives have occurred, then one quarter of the isotope remains.
Therefore, the strontium - 90 will be at a safe level in 54 years.