Bond energies can be used to estimate the energy of a reaction. Why is this only an estimate? A) It's difficult to measure such a smal amount of energy.

B) The bonds in all molecules are the same, but not all molecules have bonds that are easily measured.

C)The same bond in a different molecule has a different energy. For example, O-H in water versus ethanol has different energies.

D) It's difficult to isolate an individual bond.

C)The same bond in a different molecule has a different energy. For example, O-H in water versus ethanol has different energies.

Explanation:

This is true going by the the statement about the bond energies and the bonding being different among the various elements. In the example given which is between ethanol and water, the bonds which exist among the elements is stronger in water than in ethanol. That is why, ethanol is easily combustible than water.

The same bond in a different molecule has a different energy. For example, O-H in water versus ethanol has different energies.

Explanation:

not clear

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.