A = mass number which is equal to the total number of protons + number of neutrons, Z= atomic number of any element which is also indicates Number of protons or number of electron in the given atom.
The formula to calculate neutron would be :
mass number - proton
31 - 15 = 16
Thus 16 neutrons are found in one atom of P
There are 4 atom in one molecule
Thus
4 atom /1 molecule * 9 molecule * 16 neutron / 1 atom
= 4*9*16= 576 neutrons
When’s I would like to say that it may be B because
You are correct, but you needn't worry about the signs so much. Just remember that the negative sign is used to denote a loss of energy; since the water is hotter, it will be losing energy (-Q) and the iron will gain energy (Q). Now, we substitute the values:
-149.3 * 4.184 * (T - 95) = 412 * 0.44 * (T - 5)
Solving this equation for T,
T = 74.8 °C
