These properties result from the regular arrangement of the ions in the crystalline lattice and from the strong electrostatic attractive forces between ions with opposite charges. They are not easily deformed, and they melt at relatively high temperatures. Ionic compounds are usually rigid, brittle, crystalline substances with flat surfaces that intersect at characteristic angles. Metal ores are commonly combinations of metal atoms with oxygen atoms, and this combination is produced when metals rust, so the process where electrons are transferred to the oxygen atoms from the metal atoms is known as oxidation of the metal and the reverse process, where pure metals are produced is called reduction of the ore to the metal. The reaction of a metal with a nonmetal usually produces an ionic compound that is, electrons are transferred from the metal to the nonmetal. To understand the relationship between the lattice energy and physical properties of an ionic compound.Note: The negative sign indicates that the lattice energy is released as heat during the formation of CaCl2.\( \newcommand\) Therefore, the lattice energy of CaCl2 is approximately -2963.7 kJ/mol. The lattice energy, ΔH5, can be calculated by subtracting the sum of the enthalpies from the formation enthalpy: Now, we need to find the lattice energy, ΔH5, which is the energy released when one mole of CaCl2(s) is formed from gaseous ions. The enthalpies given (ΔH1, ΔH2, ΔH3, ΔH4) can be labeled on the diagram accordingly. Start with Ca(s) at the bottom and draw vertical arrows upward for each step, representing the enthalpy change for that step. Combining one mole of Ca2+(g) and 2 moles of Cl-(g) to form one mole of CaCl2(s) (lattice energy, ΔH5 = ?)Ĭonstruct an enthalpy diagram with the different steps of the formation reaction. Dissociating one mole of Cl2(g) molecules to form 2 moles of Cl atoms (bond dissociation energy of Cl2, ΔH4 = 2 * 242.6 kJ/mol) Ionizing one mole of Ca+ to form Ca2+(g) (second ionization energy, ΔH3 = 1146 kJ/mol) Ionizing one mole of Ca atoms to form Ca+(g) (first ionization energy, ΔH2 = 589.5 kJ/mol) Vaporizing one mole of Ca(s) (ΔH1 = 192 kJ/mol) The formation of CaCl2 involves several steps: Break down the enthalpy change into individual steps. The formation of CaCl2 can be represented by the following equation:Ĭa(s) + Cl2(g) → CaCl2(s) ΔHf = -795 kJ/molĢ. To calculate the lattice energy of CaCl2 using an enthalpy diagram, we need to understand the steps involved in the formation of the compound and then use the given information to calculate the lattice energy.ġ. But hey, if you can solve this problem, you deserve a standing ovation! Good luck, my scientific friend! Just remember, it's a twisted path filled with calculations and numbers. So, put all these values into the equation, do some math magic, and you'll find the lattice energy of CaCl2. These ionization energies represent the amount of energy needed to remove the first and second electrons from a calcium atom, like trying to pull a stubborn clown nose off your face. ΔH1 and ΔH2 are the ionization energies of calcium, which are 589.5 kJ/mol and 1146 kJ/mol, respectively. Here, ΔHformation is the standard heat of formation of CaCl2, which is given as -795 kJ/mol. The lattice energy can be calculated using the equation: This is where the lattice energy comes into play. Step 3: We bring together the gaseous Ca atoms and Cl atoms to form CaCl2(s). Imagine Cl2 as a clingy couple that needs to break up - it's going to take some serious energy! This process requires the bond energy of Cl2, which is 242.6 kJ/mol. Step 2: We need to dissociate Cl2(g) into individual Cl atoms. It's like putting Ca(s) in a sauna and watching it turn into steam - very relaxing! This step requires the energy of vaporization for Ca(s), which is given as 192 kJ/mol. Step 1: We need to convert Ca(s) to gaseous Ca atoms. Think of it like a recipe for a disaster. To calculate the lattice energy, we need to break down the formation of CaCl2 into three steps. We have Ca(s), which needs 192 kJ/mol to vaporize, Cl2(g), which has a bond energy of 242.6 kJ/mol, and Cl(g), which has an electron affinity of -348 kJ/mol. But hey, don't worry, I'm here to guide you through this enthalpy diagram extravaganza!įirst things first, let's take a look at the key elements in this calculation. Well, calculating the lattice energy of CaCl2 can be quite a laborious process! In fact, the process is more complicated than changing your Netflix password after a messy breakup.
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