Explanation:
The species with a positive charge over it, which means lack of electrons are called cations. Whereas the species with negative over it, meaning it has an excess of electrons with it are called anions.
From the list given the cations are
H+, Ba2+, Hg2+, Li+, Ca2+ and Fe2+
Whereas anions from the list are
O-2, Br-5, F-, S-2.
A Combination of cation and anions make an ionic compound in which cation is written first and then anion.
Answer: (3)
Medeleev arranged elements in order of increasing atomic weight and similar properties
He noticed that similar elements were grouped together by using this.
<u>Answer:</u> The
for the reaction is -1052.8 kJ.
<u>Explanation:</u>
Hess’s law of constant heat summation states that the amount of heat absorbed or evolved in a given chemical equation remains the same whether the process occurs in one step or several steps.
According to this law, the chemical equation is treated as ordinary algebraic expressions and can be added or subtracted to yield the required equation. This means that the enthalpy change of the overall reaction is equal to the sum of the enthalpy changes of the intermediate reactions.
The given chemical reaction follows:

The intermediate balanced chemical reaction are:
(1)

(2)

The expression for enthalpy of the reaction follows:
![\Delta H^o_{rxn}=[1\times \Delta H_1]+[1\times (-\Delta H_2)]](https://tex.z-dn.net/?f=%5CDelta%20H%5Eo_%7Brxn%7D%3D%5B1%5Ctimes%20%5CDelta%20H_1%5D%2B%5B1%5Ctimes%20%28-%5CDelta%20H_2%29%5D)
Putting values in above equation, we get:

Hence, the
for the reaction is -1052.8 kJ.