In a reversible reaction,a catalyst is a substance that .....

For the reaction $N_2 + 3H_2 \rightleftharpoons 2NH_3 + 21.9 \, kcal$,under which conditions is the production of ammonia favored according to Le Chatelier's principle?

The increase of pressure on the ice $\rightleftharpoons$ water system at constant temperature will lead to:

The colour of $CrO_4^{2-}(aq.)$ is not changed by:

State Le Chatelier's Principle.

When a sample of $NO_2$ is placed in a container,this equilibrium is rapidly established: $2NO_{2(g)} \rightleftharpoons N_2O_{4(g)}$. If this equilibrium mixture is a darker colour at high temperatures and at low pressure,which of these statements about the reaction is true?