What is the number of molecules of c2h5oh in a 3m solution that contains 4.00kg h2o?

 The number  of C2H5OH  in a 3 m solution that contain 4.00kg H2O is calculate as below

M = moles of the solute/Kg  of water

that is 3M = moles of solute/ 4 Kg
multiply  both side by  4

moles of the  solute  is therefore = 12  moles

by use of Avogadro law constant

1 mole =6.02 x10^23  molecules

what  about 12 moles

=12 moles/1 moles  x 6.02 x10^23 = 7.224 x10^24 molecules

"electrical energy" transforms to "thermal energy".hope my answer has you : )