That when water is boiled in a open beaker and it disappears that it evaporates into the air
B
Explanation:
Burning is a chemical change and cutting grass is a physical change
Answer:
Bond energy of carbon-fluorine bond is 485 kJ/mol
Explanation:
Enthalpy change for a reaction, is given as:
![\Delta H_{rxn}=\sum [n_{i}\times (E_{bond})_{i}]-\sum [n_{j}\times (E_{bond})_{j}]](https://tex.z-dn.net/?f=%5CDelta%20H_%7Brxn%7D%3D%5Csum%20%5Bn_%7Bi%7D%5Ctimes%20%28E_%7Bbond%7D%29_%7Bi%7D%5D-%5Csum%20%5Bn_%7Bj%7D%5Ctimes%20%28E_%7Bbond%7D%29_%7Bj%7D%5D)
Where
and
represents average bond energy in breaking "i" th bond and forming "j" th bond respectively.
and
are number of moles of bond break and form respectively.
In this reaction, one mol of C=C, four moles of C-H and one mol of F-F bonds are broken. One mol of C-C bond, four moles of C-H bonds and two moles of C-F bonds are formed
So, 
or, 
or, 
So bond energy of carbon-fluorine bond is 485 kJ/mol
A, because the shape of it forms and arc much like a H2O molecule.