it´s actually Lithium and fluorine / Magnesium and Chlorine / Beryllium and Nitrogen
Q1)
the number of moles can be calculated as follows
number of moles = mass present / molar mass
number of moles is the amount of substance.
4.8 g of Ca was added therefore mass present of Ca is 4.8 g
molar mass of Ca is 40 g/mol
molar mass is the mass of 1 mol of Ca
therefore if we substitute these values in the equation
number of moles of Ca = 4.8 g / 40 g/mol = 0.12 mol
0.12 mol of Ca is present
q2)
next we are asked to calculate the number of moles of water present
again we can use the same equation to find the number of moles of water
number of moles = mass present / molar mass
3.6 g of water is present
sum of the products of the molar masses of the individual elements by the number of atoms
H - 1 g/mol and O - 16 g/mol
molar mass of water = (1 g/mol x 2 ) + 16 g/mol = 18 g/mol
molar mass of H₂O is 18 g/mol
therefore number of moles of water = 3.6 g / 18 g/mol = 0.2 mol
0.2 mol of water is present
The molar mass of NH3
N = 14
H3 = 3
total = 17
The fraction of nitrogen is 14/17
So 14/17 x 125 = 102.94g
Answer :
Standard enthalpy of formation : It is defined as the enthalpy change for the reaction that forms one mole of compound from its elements. All the substances in their standard states.
The balanced chemical equation for the reaction is,
In the balance reaction, Strontium (Sr), Carbon (C) and Strontium carbonate 
are in solid state and oxygen is in gaseous state.
