This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
ScanSolve AI Answer
You're on a roll — Part (d): Enthalpy Change of Combustion of Ethane d) (i) Calculate the enthalpy change for the combustion of ethane (C_2H_6) using the bond enthalpy data. Step 1: Write the balanced chemical equation for the combustion of ethane. C_2H_6(g) + (7)/(2)O_2(g) → 2CO_2(g) + 3H_2O(g) Step 2: Identify bonds broken and bonds formed, and their respective bond enthalpies. Bonds broken (reactants): • 1 C-C bond: 1 × 347 kJ/mol = 347 kJ • 6 C-H bonds: 6 × 411 kJ/mol = 2466 kJ • (7)/(2) O=O bonds: 3.5 × 498 kJ/mol = 1743 kJ Total energy absorbed to break bonds = 347 + 2466 + 1743 = 4556 kJ Bonds formed (products): • 4 C=O bonds (in 2CO_2): 4 × 805 kJ/mol = 3220 kJ • 6 O-H bonds (in 3H_2O): 6 × 464 kJ/mol = 2784 kJ Total energy released when forming bonds = 3220 + 2784 = 6004 kJ Step 3: Calculate the enthalpy change ( H). H = (Bond energies of bonds broken) - (Bond energies of bonds formed) H = 4556 kJ - 6004 kJ = -1448 kJ/mol The enthalpy change for the combustion of ethane is -1448 kJ/mol. d) (ii) Suggest why this value differs from the data book value of -1560 kJ/mol for the enthalpy of combustion of ethane. The calculated value uses average bond enthalpies, which are values averaged across many different compounds. The actual bond energies in a specific molecule like ethane can differ slightly from these average values due to the specific molecular environment. Additionally, standard enthalpy of combustion values often refer to water in its liquid state, whereas bond enthalpy calculations typically assume all species are in the gaseous state. Part (e): Unit Cells e) (i) What is a centered unit cell? A centered unit cell is a type of unit cell in a crystal lattice that contains constituent particles (atoms, ions, or molecules) at positions other than just the corners. These additional particles are located either at the center of the unit cell or at the center of its faces. e) (ii) List two types of centered unit cells. • Body-centered cubic (BCC) • Face-centered cubic (FCC) What's next? 📸