Aluminum metal reacts wiht chlorine with a spectacular display of sparks: 2 Al(s) + 3 Cl2(g) → 2 AlCl3(s) ΔH° = -1408.4 kJ How much heat in kilojoules is released on reaction of 5.00 g of Al?

Verified step by step guidance

1. Determine the molar mass of aluminum (Al) using the periodic table.
2. Calculate the number of moles of aluminum in 5.00 g using the formula: \( \text{moles of Al} = \frac{\text{mass of Al}}{\text{molar mass of Al}} \).
3. Use the stoichiometry of the balanced chemical equation to find the moles of \( \text{AlCl}_3 \) produced per mole of Al reacted.
4. Calculate the heat released using the enthalpy change (\( \Delta H^\circ \)) given in the reaction: \( \text{heat released} = \text{moles of Al} \times \frac{-1408.4 \text{ kJ}}{2 \text{ moles of Al}} \).
5. Express the final answer in kilojoules, ensuring the correct sign for heat released.

Key Concepts

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced equation. It allows us to determine the amount of substance consumed or produced in a reaction. In this case, we need to use the molar ratios from the balanced equation to relate the mass of aluminum to the heat released.

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat absorbed or released during a chemical reaction at constant pressure. A negative ΔH indicates that the reaction is exothermic, meaning it releases heat. In this reaction, the ΔH° value of -1408.4 kJ indicates that this amount of heat is released when 2 moles of Al react with chlorine.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For aluminum, the molar mass is approximately 26.98 g/mol. To find out how much heat is released from 5.00 g of Al, we first convert grams to moles using the molar mass, which allows us to apply stoichiometry to calculate the corresponding heat released.