Here are the solutions: 
For NaCl, there would be one electron transferred from the sodium atom, now producing a cation to the chlorine atom resulting in a chlorine anion. Forming ionic bond. 
For CaS, there would be 2 electrons transferred from an atom of Ca to S, this can be obtained by simply looking at the ionic charges and or combining capacities of Ca. 
For BaO, likewise, 2 electrons that are valence electrons are transferred from Ba to Oxygen. 
In the ionic compound of KBr, the atom of K, potassium donated its one valence electron to Br, in need of it to achieve a stable octet, and produce the chemical bond. 
Finally, LiF, a single valence electron is transferred from a metal atom of Li to F, for both of the atoms that would form the ionic bond to achieve a stable octet, and or full electron shell.
        
             
        
        
        
Answer : The enthalpy of formation of  is, -812.4 kJ/mole
 is, -812.4 kJ/mole
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 formation of  will be,
 will be,
 
    
The intermediate balanced chemical reaction will be,
(1)  
     
(2)  
    
(3)  
    
(4)  
    
Now adding all the equations, we get the expression for enthalpy of formation of  will be,
 will be,



Therefore, the enthalpy of formation of  is, -812.4 kJ/mole
 is, -812.4 kJ/mole
 
        
             
        
        
        
It seems like the answer is C, you really just need to use the process of elimination.
 
        
             
        
        
        
Answer:
Explanation:
3.
Knowns: 100mL of solution; concentration of 0.7M
Unknown: number of moles
Equation: number of moles = volume * concentration
Plug and Chug: number of moles = 100/1000 * 0.7 = 0.07 mole
Final Answer: 0.07mole
2.
Knowns: 5.50L of solution; concentration of 0.400M
Unknown: number of moles
Equation: number of moles = volume * concentration
Plug and Chug: number of moles = 5.5 * 0.4 = 2.20 mole
Final Answer: 2.20 mole
 
        
                    
             
        
        
        
Answer: A
Explanation: Protons and neutrons form the nucleus of the atom, with electrons orbiting it.