For the reaction: 2NO2(g) → N2O4(l), the ΔH of the reactants, two moles of NO2 (g), is + 66 kJ/mol,
and the ΔH of the products, N2O4 (l), is -20 kJ/mol.
Which of the following shows the ΔH (change in enthalpy) for the reaction as a whole?

Question 8 options:

ΔrxnH =(- 20 kJ/mol) / (+66 kJ/mol)

ΔrxnH = (+66 kJ/mol) + (- 20 kJ/mol)

ΔrxnH =(+66 kJ/mol) - (- 20 kJ/mol)

ΔrxnH =(-20 kJ/mol) - (+ 66 kJ/mol)

Consider the elements bromine and chlorine; which elements has a larger ionic radius ?

How do you determine the percent yield of a chemical reaction

1.) which of the following is a molecule but not a compound? a.he b.f2 c.h2o d.ch4 2.) what is a physical combination of substances? a.a compound b.a molecule c.a mixture d.an element 3.) what is a chemical combination of substances? a.a compound b.an atom c.a mixture d.an element 4.) what is the relationship between the solute and solvent in a solution? a.they form a compound b.they form a mixture c.they form molecules d.they form chemical bonds 5.) the gases in air dissolve in water. what would be one way to reduce the amount of a gas dissolved in water? a.add more water b.reduce the air pressure c.increase the air pressure d.stir the water 6.) how would you determine the solubility of a substance? a.find how well it dissolved various substances. b.find the mass and the volume of the substance. c.find the temperature at which the substance evaporated. d.find how much i was able to dissolve in a solute. 7.) the periodic table organizes all of the kinds of a.molecules. b.compounds. c.atoms. d.ions. 8.)what distinguishes two substances combined to become a compound vs. two substances combined to become a mixture? a.whether they can be easily separated b.whether they chemically bond together c.whether they both are visible d.whether they are heterogeneous 9.) the principle components of air are: n2 78% o2 21% ar 0.95% co2 0.038% this is a solution of a.molecules and atoms. b.molecules. c.compounds and molecules. d.atoms.