Nitrogen Chemistry and Kc

What is the haber process and is it ^H+ve or ^H-ve

N2 + 3H2 <=> 2NH3

^H-ve

Why is Nitrogen gas very unreactive

Contains triple bond which is very difficult to break

What is the name, appearance and source of N2O

N2O

Dinitrogen (I) Oxide

Colourless gas

Bacteria in soil

What is the name, appearance and source of NO

Nitrogen (II) Oxide, Colourless gas, Car exhaust/Lightning

What is the name, appearance and source of NO2

Nitrogen (IV) dioxide, Brown gas (toxic), Oxidation of NO in air

What is NO3- and NO2-

NO3- = Nitrate (V)

NO2- = Nitrate (III), contains a lone pair

What is the chemical test for nitrate (V) ions (NO3-)

• Add NaOH(aq)

• Add Devarda’s Alloy

• Warm gently

• Test gases with damp red litmus paper

• Gas evolved (NH3) turns blue

3NO3- + 8Al + 18H2O + 5OH- —> 3NH3 + 8[Al(OH)4]

What is the chemical test for ammonium ions

• Add NaOH(aq)

• Warm gently

• Test gases with damp red litmus paper

• Paper turns blue if NH3 is formed

NH4+ + OH- —> NH3 + H2O

If Kc is large, the position of the equilibrium to to the ___, so there are more _______, and a _______ yeild

If Kc is large, the position of the equilibrium to to the RHS, so there are more Products, and a High yeild

If Kc is small, the position of the equilibrium to to the ___, so there are more _______, and a _______ yeild

If Kc is small, the position of the equilibrium to to the LHS, so there are more reactants, and a low yeild

How can Kc be determined experimentally

• Measure starting quantities accurately.

• Allow the reaction to reach equilibrium (use a catalyst if needed).

• Control and measure the temperature (e.g., with a water bath).

• After a set period (e.g., 1 week), take a sample.

• Determine the concentration of one component (e.g., by titration, pH measurement, or colorimetry).

• Calculate moles and concentrations of all species.

• Calculate Kc using the equilibrium concentrations.

• Repeat sampling at intervals until the Kc value remains constant, confirming equilibrium is reached

How does temperature affect Kc and Equilibrium

• Exothermic reactions: Increasing temperature shifts equilibrium to the left, so Kc decreases.

• Endothermic reactions: Increasing temperature shifts equilibrium to the right, so Kc increases.

How does pressure affect Kc and Equilibrium

• Kc stays the same when pressure changes.

• Changing pressure only affects the concentrations of reactants and products temporarily.

• If you increase the total pressure, the equilibrium shifts toward the side with fewer moles of gas to reduce the pressure.

• To keep Kc unchanged, the ratio of concentrations adjusts (top increases, bottom decreases proportionally).

• Decreasing pressure does the opposite—shifts equilibrium to the side with more gas molecules (in this case, to the LHS).

How do catalysts affect Kc

• Catalysts do not change Kc.

• They speed up the rate at which equilibrium is reached but do not affect the position of equilibrium.