Answer:
d. Sum of product enthalpies minus the sum of reactant enthalpies
Explanation:
The standard enthalpy change of a reaction (ΔH°rxn) can be calculated using the following expression:
ΔH°rxn = ∑n(products) × ΔH°f(products) - ∑n(reactants) × ΔH°f(reactants)
where,
ni are the moles of products and reactants
ΔH°f(i) are the standard enthalpies of formation of products and reactants
Density is equal to the ratio of mass to the volume.
The mathematical expression is given as:
Density of silver metal bar=
Convert 
into g/L
= 0.001 L
Thus, density = 
= 
Volume = 0.5 L
Put the values,
=
Now, convert gram into kg
1 g = 0.001 kg
Therefore, mass in kg= 
= 5.25 kg
Thus, mass of silver metal bar in kg=5.25 kg
<u>Answer:</u> The initial molarity of cation is 2.38 M
<u>Explanation:</u>
To calculate the molarity of solution, we use the equation:
We are given:
Given mass of 
= 46.3 g
Molar mass of = 129.6 g/mol
Volume of solution = 150 mL
Putting values in above equation, we get:
1 mole of produces 1 mole of 
cation and 1 mole of 
anion
So, molarity of cation = (1 × 2.38) = 2.38 M
Hence, the initial molarity of cation is 2.38 M
The balanced equation for the reaction is as follows;
2Fe + 3S ---> Fe₂S₃
molar ratio of Fe to Fe₂S₃ is 2:1
mass of Fe₂S₃ to be produced is - 96 g
therefore number of moles of Fe₂S₃ to be produced is - 96 g / 208 g/mol
number of Fe₂S₃ moles = 0.46 mol
according to the molar ratio
when 2 mol of Fe reacts with 3 mol of sulfur then 1 mol of Fe₂S₃ is produced
that for 1 mol of Fe₂S₃ to be produced - 2 mol of Fe should react
therefore for 0.46 mol of Fe₂S₃ to be produced - 2 x 0.46 = 0.92 mol of Fe is required
mass of Fe required - 0.92 mol x 56 g/mol = 51.5 g
mass of Fe required is - 51.5 g
The change in internal energy that accompanies the transfer of heat (q) or work (w), into or out of a system can be calculated using the following equation: Note the value of heat and work as they are transferred into or out of a system.
