Answer : The enthalpy change of reaction is 206.9 kJ
Explanation :
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The given final reaction is,

The intermediate balanced chemical reaction will be,
(1)

(2)

First we will reverse the reaction 1 and 2 then adding both the equation, we get :
(1)

(2)

The expression for final enthalpy is,



Therefore, the enthalpy change of reaction is 206.9 kJ
Answer:
C. Their properties change completely.
Explanation:
The electron configurations of the elements show a periodic variation with increasing atomic number. Consequently, there are also periodic variations in physical and chemical behavior.
When atoms interact to form a chemical bond, they combine in order to <u>achieve a more stable electron configuration.</u> As a consequence, the compounds formed exhibit completely different properties.
For example, when solid magnesium burns in air, it forms both magnesium oxide and magnesium nitride, which are gases.
Answer:
Your two answers are numbers of protons and electron and the second one is the atomic mass and weight.
Explanation:
God bless you are you got this
Finding neutrons = Mass number - proton number.
For finding neutrons for phosphorus = 31-15
=16.