For a chemical reaction to occur, all of the following must happen except

A solid sample at room temperature spontaneously sublimes forming a gas. This change in state is accompanied by which of the changes in the sample?

In the reaction energy diagrams shown, reaction A is _____, and it occurs _____ reaction B.

How many grams of CO2 will be produced when 9.00 grams of Na2SO4 react according to the balanced reaction shown?               Na2SO4 + 2 C → Na2S + 2 CO2

In the following reaction which species is being oxidized and which is being reduced? 2 Cr (s) + 3 Cl2 (g) → 2 CrCl3 (s)

3120kJ/mol of heat is released in the reaction of benzene (C6H6)  with oxygen gas.  Is this reaction exothermic or endothermic?

How many grams of fluorine (F2) are required to produce 40.0 grams of FeF3 from the reaction shown?               2 Fe + 3F2 → 2 FeF3

When the following reaction is balanced the coefficient in front of oxygen is: ____ C8H18 + ____ O2 → ____ CO2 + ____ H2O

For the reaction of zinc with silver nitrate,  2.9 g of silver was produced.  The reaction should have theoretically produced 3.5 g.  What is the percent yield?

The position of the equilibrium for a system where K = 4.6 × 10-15 can be described as being favored to _____; the concentration of products is relatively _____.