Determine how much heat is evolved or absorbed when 20.0 of lithium iodide completely dissolves in water.
What information do you have or what information can you obtain?
delta Hsolution = delta Hhydration - delta Hcrystal lattice
To determine how much heat is evolved or absorbed when 20.0 g of lithium iodide (LiI) completely dissolves in water, we need to use the concept of enthalpy change.
First, we need to find the balanced chemical equation for the dissolution of LiI in water:
LiI(s) → Li+(aq) + I-(aq)
Next, we need to find the enthalpy change per mole of the substance. This information can typically be found in a reference table or a chemistry textbook. In this case, the enthalpy change for dissolving LiI is -60.5 kJ/mol.
Now, we can calculate the heat evolved or absorbed when 20.0 g of LiI dissolves in water.
1. Determine the number of moles of LiI.
To calculate the number of moles, we use the molar mass of LiI, which is 133.84 g/mol.
Moles of LiI = Mass (g) / Molar mass (g/mol)
Moles of LiI = 20.0 g / 133.84 g/mol
Moles of LiI = 0.1496 mol
2. Calculate the heat change using the molar enthalpy.
Heat change = Moles of LiI * Enthalpy change per mole
Heat change = 0.1496 mol * -60.5 kJ/mol
Heat change = -9.05 kJ
Therefore, when 20.0 g of lithium iodide completely dissolves in water, approximately 9.05 kJ of heat is absorbed.
To determine how much heat is evolved or absorbed when lithium iodide completely dissolves in water, we need to use the concept of enthalpy change (ΔH).
The enthalpy change of a chemical reaction can be calculated using the equation:
ΔH = q / n
where ΔH represents the enthalpy change in Joules (J), q represents the heat absorbed or released in Joules (J), and n represents the number of moles of reactants or products.
In this case, we need to first calculate the number of moles of lithium iodide (LiI) that completely dissolves in water:
Number of moles (n) = mass / molar mass
The molar mass of LiI can be calculated by adding the atomic masses of lithium (Li) and iodine (I) together:
Molar mass of LiI = atomic mass of Li + atomic mass of I
Once you have calculated the number of moles of LiI completely dissolving in water, you will also need the heat absorbed or released (q) during the process.
From experimental data, it is known that the dissolution of 1 mole of lithium iodide in water is exothermic and releases approximately -42 kilojoules of heat (-42 kJ).
Now, you can use the calculated number of moles (n) to find the total amount of heat evolved or absorbed:
Heat evolved/absorbed (q) = ΔH × n
Substituting the values into the equation, you can determine the heat evolved or absorbed when 20.0 grams of lithium iodide completely dissolves in water.