How much heat is released when a mixture containing 12.6 g CS2 and 12.6 g Cl2 reacts by the following equation?
CS2(g) + 3 Cl2(g) → S2Cl2(g) + CCl4(g)
ΔH° = −230. kJ
To determine the amount of heat released during a reaction, you need to use the concept of stoichiometry and the balanced chemical equation. Here's how you can calculate the heat released in this reaction:
Step 1: Calculate the number of moles of CS2 and Cl2.
Given masses of CS2 and Cl2 are 12.6 g each, we need to convert these masses to moles. To do so, divide the mass by the molar mass:
Molar mass of CS2 = 12.01 g/mol (C) + 32.07 g/mol (S) × 2 = 76.14 g/mol
Molar mass of Cl2 = 35.45 g/mol (Cl) × 2 = 70.9 g/mol
Number of moles of CS2 = mass of CS2 / molar mass of CS2
= 12.6 g CS2 / 76.14 g/mol CS2
Number of moles of Cl2 = mass of Cl2 / molar mass of Cl2
= 12.6 g Cl2 / 70.9 g/mol Cl2
Step 2: Determine the limiting reactant.
To find the limiting reactant, compare the number of moles of CS2 and Cl2 present in the reaction. The reactant that produces a lesser number of moles of the desired product is the limiting reactant.
In this case, we need to compare the moles of CS2 and Cl2 using their stoichiometric coefficients from the balanced equation (CS2:Cl2 = 1:3). Identify the limiting reactant by dividing the number of moles by the stoichiometric coefficient:
Moles of S2Cl2 formed = moles of CS2 × 1 (stoichiometric coefficient of CS2)
= moles of CS2 × 1
Moles of CCl4 formed = moles of Cl2 × 3 (stoichiometric coefficient of Cl2)
= moles of Cl2 × 3
Compare the moles of S2Cl2 and CCl4 to determine the limiting reactant.
Step 3: Calculate the heat released.
To calculate the heat released, we use the equation:
Heat released = moles of limiting reactant × ΔH° of the reaction
Since the limiting reactant determines the amount of product formed, we use its moles in the calculation.
Heat released = moles of limiting reactant × ΔH°
= moles of limiting reactant × -230 kJ (given ΔH° value)
Substitute the moles of the limiting reactant that you determined in Step 2 into the equation and calculate the value of heat released.
This process will give you the amount of heat released in kJ during the reaction between CS2 and Cl2.