Please correct me if I'm wrong but I think the answer is b or c
also sorry if i do get it wrong
Answer:
3 moles
Explanation:
To solve this problem we will use the Avogadro numbers.
The number 6.022×10²³ is called Avogadro number and it is the number of atoms, ions or molecules in one mole of substance. According to this,
1.008 g of hydrogen = 1 mole = 6.022×10²³ atoms.
18 g water = 1 mole = 6.022×10²³ molecules
we are given 36 g of C-12. So,
12 g of C-12 = 1 mole
24 g of C-12 = 2 mole
36 g of C-12 = 3 mole
So 3 moles of C-12 equals to the number of particles in 36 g of C-12.
Answer : The enthalpy of the given reaction will be, -1048.6 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.
The main reaction is:

The intermediate balanced chemical reactions are:
(1)

(2)

(3)

(4)

(5)

Now reversing reaction 2, multiplying reaction 3 by 4, reversing reaction 1 and multiplying by 2, reversing reaction 5 and multiplying by 2 and then adding all the equations, we get :
(1)

(2)

(3)

(4)

(5)

The expression for enthalpy of main reaction will be:



Therefore, the enthalpy of the given reaction will be, -1048.6 kJ
Answer:1 mol of Mg(NO3)2 contains 6.022*10^23 molecules
3 mol Mg(NO3)2 contains 3*6.022*10^23 = 1.81*10^24 molecules
Each Mg(NO3)2 molecule contains 2 N atoms
Number of N atoms = 2*1.81*10^24 = 3.62*10^24 N atoms.