#### Lechateliers Principle

1
2
3
4
5
6
7
8

Nitrogen dioxide, NO2, is a dark brown gas that is used to make nitric acid and to bleach flour. Nitrogen dioxide has a boiling point of 294 K at 101.3 kPa. In a rigid cylinder with a movable piston, nitrogen dioxide can be in equilibrium with colorless dinitrogen tetroxide, N2O4. This equilibrium is represented by the equation below.

2NO2(g) ⇌ N2O4(g) + 58 kJ

9

An equilibrium system in a sealed, rigid container is represented by the equation below.

CO(g) + H2O(g) ⇌ CO2(g) + H2(g)

10

Stamping an identification number into the steel frame of a bicycle compresses the crystal structure of the metal. If the number is filed off, there are scientific ways to reveal the number.

One method is to apply aqueous copper(II) chloride to the number area. The Cu2+ ions react with some iron atoms in the steel frame, producing copper atoms that show the pattern of the number. The ionic equation below represents this reaction.

Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s)

Another method is to apply hydrochloric acid to the number area. The acid reacts with the iron, producing bubbles of hydrogen gas. The bubbles form faster where the metal was compressed, so the number becomes visible. The equation below represents this reaction.

2HCl(aq) + Fe(s) → FeCl2(aq) + H2(g)

11

The equation below represents an equilibrium system of SO2(g), O2(g), and SO3(g). The reaction can be catalyzed by vanadium or platinum.

2SO2(g) + O2(g) ⇌ 2SO3(g) + energy

12

A student makes an aqueous solution of lactic acid. A formula for one form of lactic acid is shown below. The solution is placed in a sealed flask to be used in a laboratory investigation. The equation below represents the lactic acid equilibrium system in the flask. 13

Common household bleach is an aqueous solution containing hypochlorite ions. A closed container of bleach is an equilibrium system represented by the equation below.

Cl2(g) + 2OH(aq) ⇌ ClO(aq) + Cl(aq) + H2O(ℓ)

14