Chemical industry Flashcards
What is the rate of reaction?
The rate of reactant-to-product conversion, calculated as the gradient of a concentration-time graph.
What is the general form of the rate equation?
rate = k[A]^a[B]^b, where k is the rate constant, [X] is the concentration, and a, b are the orders of reactants.
What happens to the rate constant (k) as temperature increases?
The rate constant (k) increases with temperature.
What is the order of a reaction?
An integer determined experimentally that shows how the rate depends on the concentration of a specific reactant.
What is overall order in a reaction?
The sum of all individual orders in the reaction.
How can you determine the order of a reactant?
Measure how the rate changes as the concentration of that reactant doubles, ensuring other reactants are in excess.
What is a zero-order reaction?
A reaction where the rate is independent of the concentration of the reactant.
What is a first-order reaction?
A reaction where the rate is directly proportional to the concentration of the reactant.
What is a second-order reaction?
A reaction where the rate is proportional to the square of the concentration of the reactant.
What is reaction half-life?
The time it takes for half of a reactant to be used up.
What does a constant half-life indicate?
A first-order reaction.
What is the equation to calculate the rate constant (k) for first-order reactions?
k = ln(2) / t1/2 (units: s⁻¹).
What is the initial rate of reaction?
The rate at the start of the reaction, calculated as amount of reactant used or product formed divided by time.
What is a clock reaction?
A reaction with a clear endpoint (e.g., a color change), useful for measuring the initial rate of reaction.
Describe the iodine clock reaction.
H₂O₂ + 2I⁻ + 2H⁺ → 2H₂O + I₂, where sodium thiosulfate removes I₂ until it is used up, producing a color change with starch.
What does a zero-order concentration-time graph look like?
A straight line with a negative gradient.
What does a first-order concentration-time graph look like?
An exponential decay curve.
What does a second-order concentration-time graph look like?
A steeper exponential decay curve than first order.
What does a zero-order rate-concentration graph look like?
A horizontal line (rate is constant regardless of concentration).
What does a first-order rate-concentration graph look like?
A straight line with a positive gradient.
What does a second-order rate-concentration graph look like?
A quadratic curve.
What is the Arrhenius equation?
k = Ae^(-Ea/RT), where k is the rate constant, Ea is activation enthalpy, T is temperature (K), R is the gas constant, and A is the pre-exponential factor.
How can the Arrhenius equation be rearranged for plotting?
ln(k) = -Ea/RT + ln(A), allowing a plot of ln(k) against 1/T with gradient -Ea/R.
What is the rate-determining step?
The slowest step in a multi-step reaction, determining the overall reaction rate.
What does it mean if a reactant is not in the rate equation?
The reactant is not involved in the rate-determining step.
How does changing pressure affect the equilibrium constant (Kc)?
Pressure does not affect Kc, but it shifts the equilibrium position toward fewer moles of gas.
How does changing concentration affect Kc?
Concentration changes shift equilibrium but do not affect the value of Kc.
How does temperature affect Kc?
Temperature changes affect both the equilibrium position and the value of Kc.
What is the effect of adding a catalyst on equilibrium?
It does not affect Kc or the equilibrium position but reduces the time taken to reach equilibrium.
How can Kc be determined experimentally?
Using colorimetry for colored substances or pH probes for acidic/alkaline equilibria.
What is the structure of nitrogen (N2)?
A diatomic molecule with a triple bond, giving it a very high bond enthalpy.
What is the structure of ammonia?
NH3 with a lone pair of electrons.
What is the formula of the ammonium ion?
NH4⁺.
What is nitrogen monoxide?
NO, a colorless gas also called nitrogen(II) oxide.
What is dinitrogen monoxide?
N2O, a colorless gas with a sweet smell, also called nitrogen(I) oxide or laughing gas.
What is nitrogen dioxide?
NO2, a brown gas with a sharp odor, also called nitrogen(IV) oxide.
How can ammonium compounds be tested?
Add NaOH and heat. Ammonia gas is released, turning damp red litmus paper blue.
How can nitrate(V) ions be tested?
Heat with NaOH and Devarda’s alloy. Ammonia gas is produced, indicating the presence of nitrate(V) ions.
What are the key steps of the nitrogen cycle?
N2 + H2 → NH3 → NH4⁺ → NO2⁻ → NO3⁻ → N2, involving reactions with oxygen, hydrogen, and electrons.
