21 which mathematical expression represents the heat of reaction for a chemical reaction? (1) (the heat of fusion) – (the heat of vaporization)
(2) (the heat of vaporization) – (the heat of fusion)
(3) (the potential energy of the products) – (the potential energy of the reactants)
(4) (the potential energy of the reactants) – (the potential energy of the products)

Achemistry student needs to standardize a fresh solution of sodium hydroxide. he carefully weighs out of oxalic acid , a diprotic acid that can be purchased inexpensively in high purity, and dissolves it in of distilled water. the student then titrates the oxalic acid solution with his sodium hydroxide solution. when the titration reaches the equivalence point, the student finds he has used of sodium hydroxide solution. calculate the molarity of the student's sodium hydroxide solution. be sure your answer has the correct number of significant digits.

What is the approximate vapor pressure when the gas condenses at 70 degrees celsius

Explain how to convert from one unit to another in the metric system.