Which of the following is correct concerning hess's law?
a. the change of enthalpy of a reaction can be found be subtracting the enthalpy of the products from the enthalpy of the reactants.
b. the change in enthalpy can be found be subtracting the enthalpy of the reactants from the enthalpy of the products.
c. the change in enthalpy can be found by adding the enthalpies of the individual thermochemical reactions of a chemical reaction.
d. the change in enthalpy can be found by subtracting the enthalpies of the individual thermochemical reactions of a chemical reaction.

The atomic radius of sodium is 186 pm and of chlorine is 100 pm. the ionic radius for na+ is 102 pm and for cl– is 181 pm. in going from na to cl in period 3, why does the atomic radius decrease while the ionic radius increases? a. the inner electrons in the sodium cation shield its valence electrons more effectively than the inner electrons in the chloride anion do. b. the inner electrons shield the valence electrons more effectively in the chlorine atom than in the chloride anion. c. the outermost electrons in chloride experience a smaller effective nuclear charge than those in the sodium cation do. d. the outermost electrons in chloride experience a larger effective nuclear charge than those in the sodium cation do. e. monatomic ions are bigger than the atoms from which they are formed.

Particles vibrate in a rigid structure and do not move relative to their neighbors.

In a laboratory, 1.55mg of an organic compound containing carbon, hydrogen, and oxygen is burned for analysis. this combustion resulted in the formation of 1.45mg of carbon dioxide and .89 mg of water. what is the empirical formula for this compound?