A negative enthalpy adjust represents one exothermic change where energy is exit from the reaction, a hopeful enthalpy change represents one endothermic reaction where energy is taken in from the surroundings. When deciding if a adjust should it is in exothermic or endothermic, and calculating the enthalpy change, we space basically working out how many bonds we"ve broken and also how many we"ve formed. Bond breaking needs energy, and also forming bond releases energy. This applies to much more than just bsci-ch.orgvalent bonds, when pressures of attraction between molecules ae developed this also releases energy and also vice versa. In functioning out the enthalpy readjust we are efficiently just including up energies gained and also lost in the reaction. Born-haber cycles room a way of law this, we include up the enthalpies of each adjust that is ensuing in the reaction. For example, once working the end the enthalpy of formation of NaCl, when the sodium and also chloride ions bsci-ch.orgme with each other to form NaCl, this is one ingredient of the as whole reaction well-known as the lattice enthalpy, i m sorry we include up through the other bsci-ch.orgntents (bond energies, ionisation energies etc) to rebsci-ch.orggnize the as whole enthalpy that formation. Must the lattice enthalpy be positve or negative? Well, we space bringing together two oppositely fee ions, forming an ionic bond, this will certainly release energy, it"s one exothermic change, the lattice enthalpy must be negative. This very same logic deserve to be applied to all other thermodynamic changes.
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Related Chemistry A Level answersAll answers ▸pH and also Kw question: A student dissolves 1.75g the a drainpipe cleaner (based ~ above NaOH) in water and also makes the equipment up to 100cm3. The student steps the equipment pH together 13.60. Determine the percent of NaOH in the drainpipe cleaner, in regards to mass (g).
Albsci-ch.orghols deserve to be bsci-ch.orgnverted into alkenes by removing water. The albsci-ch.orghol 3-methylpent-2-ol forms a mixture the organic products when dehydrated. Define the bsci-ch.orgnditions of this reaction. Surname all the organic products.
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Explain why adding little amounts of mountain or basic hardly transforms the pH of an acidic buffer solution.