Answer : The enthalpy for the reaction is 49.1 kJ/mol
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 reaction of 
will be,
The intermediate balanced chemical reaction will be,
(1) 
(2) 
(3) 
Now we will reverse the reaction 1 and divide by 2, multiply reaction 2 by 6 and reaction 3 by 3/2 then adding all the equations, we get :
(1) 
(2) 
(3) 
The expression for enthalpy of formation of will be,
Therefore, the enthalpy for the reaction is 49.1 kJ/mol
Answer:
The solution will not form a precipitate.
Explanation:
The Ksp of PbI₂ is:
PbI₂(s) ⇄ 2I⁻(aq) + Pb²⁺(aq)
Ksp = 1.40x10⁻⁸ = [I⁻]²[Pb²⁺] <em>Concentrations in equilibrium</em>
When 328mL of 0.00345M NaI(aq) is combined with 703mL of 0.00802M Pb(NO₃)₂. Molar concentration of I⁻ and Pb²⁺ are:
[I⁻] = 0.00345M × (328mL / (328mL+703mL) =<em> 1.098x10⁻³M</em>
[Pb²⁺] = 0.00802M × (703mL / (328mL+703mL) =<em> 5.469x10⁻³M</em>
<em />
Q = [I⁻]²[Pb²⁺] <em>Concentrations not necessary in equilibrium</em>
If Q = Ksp, the solution is saturated, Q > Ksp, the solution will form a precipitate, if Q < Ksp, the solution is not saturated.
Replacing:
Q = [1.098x10⁻³M]²[5.469x10⁻³M] = 6.59x10⁻⁹
As Q < Ksp, the solution is not saturated and <em>will not form a precipitate</em>.
<span>In the question ' which of the following most likely require intermolecular force', options A and C given are definitely not the correct answers. Among the items listed in the questions, the one that will most likely required an intermolecular force is a rock maintaing its solid shape. Thus, the correct option is B. Intermolecular forces are forces which maintain chemical interactions between molecules of a particular susbstance and other types of paticles that may be present in the substance. Rocks are made up of differet particles and their structures are held together by different types of intermolecular forces depending on the types of particles present in the rock. Intermolecular forces can only occur among molecules and other particles in a compound that is why the other two options are wrong. Intermolecular force can either be attractive or repulsive. Attraction occurs between molecules of opposite charges, that is, positive and negative charges while repulsion occurs between particles of like charges, for intstance, between positive and positive charges. The Intermolecular forces that exist in a compound maintaings the integrity of the structure of that compound. Intermolecular forces in compounds exist in different forms, we have electrovalent bonds, covalent bonds, hydrogen bond, vander waals forces, etc. The type of molecules that exist in a compound will determine the type of intermolecular forces that will exist among the molecules of that substance. Electrovalent bonds are the strongest type of intermolecular force and it normally exist between metals and non metals. Covalent bonds involved sharing of electrons among the participating elements while vander waals forces are the weakest form of intermolecular forces. Forces are often required to break intermolecular forces apart. Breaking the intermolecular forces apart will destroy the structure of the substance inlvolved.</span>
