The quantum efficiency for the formation of ethene from di-n-propylketone (heptan-4-one) with 313 nm light is 0.21. How many molecules of ethene per second, and moles per second, are formed when the sample is irradiated with a 313 nm light operating at 50W at that wavelength, and under conditions such that all light is absorbed by the sample

1.66×10^15

Explanation:

Energy= power×time

Power= 50W

Time= 1s

Energy= 50×1= 50J

Number of photons absorbed=Eλ/hc

E= energy of photon

λ= wavelength of photons

h= planks constant

c= speed of light

n= 50×313×10^-9/6.6×10^-34×3×10^8

n= 7.9×10^19

But quantum yield ( Ф)= number of reaction events/ number of photons absorbed

Hence:

Number of reaction events= 0.21 ×7.9×10^19= 1.66×10^15

it is the most commonly accepted one

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.