The Chemical Industry Flashcards
Rate of Reaction
The change in the amount of reactants or products per unit time.
Measuring Rate of Reaction
· pH (moldm⁻³s⁻¹)
· Gas Volume (cm³s⁻¹)
· Loss of mass (gs⁻¹)
· Colour Change
· Concentration (moldm⁻³s⁻¹)
The Rate Equation
A + B → C + D
Rate = k[A]ⁿ[B]ⁱ
n and i are the orders
k is the rate constant
Order of Reaction
The Order of a Reaction shows the number of molecules of that reactant are involved in the rate-determining step.
Zero - concentration of reactant changes and the rate is unaffected.
1st - concentration and rate are proportional.
2nd - concentration² and rate are proportional.
Half-Life of Different Orders
0 Order - Half life decreases as reaction progresses.
1st Order - Half life is constant. Rate Constant = ln2 / Half Life
2nd Order - Half life increases as reaction progresses.
Arrhenius Equation
k = Ae^(-Eₐ/RT)
lnk = -Eₐ/RT + lnA
k - Rate Constant
Eₐ - Activation Energy (Jmol⁻¹)
T - Temperature (K)
R - Gas Constant
A - Pre-Exponential Constant
Rate Determining Step
The Slowest Step in a Multi-Step Reaction.
The Reactants involved are in the rate equation.
Equilibrium Constant (Kc)
aA + bB → dD + eE
Kc = [D]^d x [E]^e / [A]^a x [B]^b
Kc = [Products] / [Reactants]
Effect of Temperature and Pressure on Kc
Pressure has no effect on Kc
Temperature does have an effect of Kc as increasing the temperature causes equilibrium to shift causing the ratio of products to reactants to change.
Why is Nitrogen very unreactive?
Nitrogen is naturally a diatomic molecule connected by a triple covalent bond.
Ammonia and the Ammonium Ion
Ammonia: NH₃
Ammonium Ion: NH₄⁺
NH₃ + H⁺ ↔ NH₄⁺
Nitrous Oxides
NO - Nitrogen Monoxide. Colourless Gas.
N₂O - Nitrous Oxide. Sweet Smell and Colourless Gas.
NO₂ - Nitrogen Dioxide. Brown, Sharp Odour, Toxic.
How do you test if an Ammonium Ion is present?
Add Sodium Hydroxide and gently heat. Ammonia Gas is produced turning damp red litmus paper blue.
NH₄⁺ + OH⁻ → NH₃ + H₂O
How to test for Nitrate (V) ions
Warm solution and add sodium hydroxide and aluminium. Produced ammonia Gas and turns Red Litmus Blue.
3NO₃⁻ + 8Al + 5OH⁻ + 18H₂O → 3NH₃ + 8[Al(OH)₄]⁻
