There’s nothing wrong with playing a game that looks like it was created in the early 1990s, but players today have become accustomed to modern game mechanics. Predict the signs of ΔS and ΔG, and explain your reasoning by drawing molecular level pictures.Warspear Online takes a very traditionalistic approach to the MMORPG genre, using old mechanics that appeal to nostalgic gameplay rather than the ground-breaking visuals and an action-packed combat system. Calcium phosphate (Ca 3(PO 4) 3) is insoluble in water.Predict the signs of ΔH, ΔS and ΔG for dissolving ammonium chloride in water (the temperature of the solution drops).Ethanol - which is infinitely soluble in water has an unfavorable enthalpy of solution the entropy of mixing is the important factor In fact many solutes dissolve in water with a decrease in temperature. In contrast when sodium chloride dissolves ΔH is positive, but ΔS is positive enough to overcome the effect of ΔH, meaning that the free energy change is also negative for this process. When calcium chloride dissolves in water ΔH is negative and ΔS is positive - the result is a large negative ΔG - and a very high solubility (595 g/L). To recap: for a solution to be formed, the free energy change must be negative. If we factor in the entropy change for the solution, which in this case is positive, then ΔG is negative - this is an “entropy driven” reaction! The question then, is why does NaCl dissolve at all? The answer is that enthalpy is (yet again) not the critical factor determining whether this process happens - it is of course entropy. That would imply that ion-ion and H 2O-H 2O interactions are stronger than the ion-water interactions for the NaCl-H 2O system. Energy from the surroundings is being used to break up the NaCl lattice and so allow ions to move into the solution. So what is going on with NaCl? Since solution temperatures decrease when NaCl is dissolved, the solution (surroundings) has lost energy to the the ion-solvent interactions (system). That is the dissolving is exothermic and heat is transferred from the system to the surroundings. If we look up the enthalpy change for the solution of calcium chloride it is around -80° kJ/mol. Therefore the interactions after the solution is formed are stronger (more stable) than those for the solid CaCl 2 and water separated. If the temperature rises, that means thermal energy is transferred from the CaCl 2-H 2O system to the water. So when we measure the temperature change, we are actually measuring the temperature change of the surroundings (not the system). The surroundings are the rest of the water molecules (that is, the solution). In this instance, the system is the CaCl 2 and the water molecules it interacts with. In order to connect our observation that the temperature increases with thermodynamic data, we have to be explicit about what we are considering the system and what is the surroundings. At the same time, the majority of the interactions between water molecules are preserved. As the crystal dissolves, new ion-dipole interactions between calcium ions and water molecules, and between chloride ions and molecules form. Within the crystal, there are ion-ion interaction while in the solvent there are H-bonding, dipole-dipole, and van der Waals interactions. The table below lists the types of interactions involved in the crystal and the solvent. Let us begin with calcium chloride: as a crystal of CaCl 2 dissolves in water, interactions between ions are broken and new interactions between and water molecules and ions and formed. Since both processes occur (all these compounds are highly soluble in water), the ΔG’s for the formation of all three solutions must be negative. How do we explain the observation that dissolving NaCl causes the temperature of the solution to decrease, while dissolving CaCl 2 or MgCl 2 makes the temperature increase? Dissolving CaCl 2 or MgCl 2 in water clearly involves some kind of energy release, if the temperature increases, the average kinetic energy of the molecules in the solution will have increased. If you dissolve calcium chloride (CaCl 2) or magnesium chloride (MgCl 2), compounds commonly used to prevent ice formation on roads, the solution gets warmer - not colder. Is this always the case with all salts? – again, sadly enough, it is not. If you add NaCl to water (you can do this at the dinner table), the NaCl will dissolve and the temperature of the solution goes down.
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