What does Hess's law state? A. The enthalpy of a reaction is positive if it is endothermic and negative if exothermic. B. The enthalpy of a reaction is the sum of the enthalpies of intermediate reactions. C. The enthalpy of a reaction can be determined only from single- step reactions. D. The enthalpy of a reaction can be measured from heat produced in a calorimeter.​

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Asample of hydrated tin (ii) chloride (sncl2) has a mass of 4.90 g. when it is dehydrated, it has a mass of 4.10 g. which is the correct chemical formula for the hydrate? sncl2•2h2o          sncl2•4h2o          sncl2•6h2o

[ou.03jthe pictures below show the wavelengths and intensities of electromagnetic radiations emitted by three stars, star 1, star 2, and star 3. intensity intensity- intensity- 1000 3500 6000 8500 11000 wavelength (a) star 1 1000 3500 6000 8500 11000 1000 3500 6000 8500 11000 wavelength (a) wavelength (a) star 2 star 3 which of these statements is correct about the color of the three stars? star 2 is white in color o star 2 is yellow in color star 1 and star 3 are yellow in color star 1 and star 3 are white in color