Explanation:
Units for $k$ are determined by dividing the units of rate by the units of the concentrations raised to their respective powers.
For a 3rd order reaction, k=mol dm−3 s−1/mol3 dm−9 = mol−2 dm6 s−1.

Explanation:
Increasing the volume decreases the pressure which shifts the position of the equilibrium to the right where there are more moles of gas.
The forward reaction is endothermic and so increasing the temperature favors this reaction.
A catalyst affects both the rate of the forward and reverse reactions equally and has no effect on the equilibrium yield.

Explanation:
Both sides of the equation have the same number of gaseous moles, so the equilibrium position is unaffected by changes in pressure.

Explanation:

The theoretical yield is the maximum amount of product that will be formed if the limiting reagent is consumed completely.

Explanation:
OH− ions react with the H+ ions, thus decreasing their concentration. The equilibrium shifts towards the reactants to produce more H+ and resist this change (Le Chatelier’s principle). This produces more yellow chromate ions.
The value of Kc is only affected by temperature so this is unchanged.

Explanation:
The number of molecules remains constant. Temperature only changes the particles’ kinetic energy; when temperature increases, the kinetic energy of the particles also increases.

Explanation:
The y-intercept = $lnA$ so must be larger for reaction 1.
The gradient (slope) is equal to −Ea/R so, must be shallower (less negative) for reaction 1.
The question is in the “hard” category as students must know how to interpret an Arrhenius plot (or correctly interpret the given equation) and compare two reactions graphically.

Explanation:
Kc>1, and so lies towards the right with the yellow product at equilibrium; the color would therefore be a pale green due to more yellow than blue.
When an acid is added, it reacts with the OH− reducing its concentration. Equilibrium shifts to the right to oppose that change.

Kc only changes with temperature. Adding an alkali would increase the OH− concentration and therefore the equilibrium would shift to the left to oppose that change. Kc again would remain the same as it is only affected by temperature.

Explanation:
The $ln(2)$ term appears because k1 is double k2, and the factor of 1000 appears in the denominator to convert J mol−1to kJ mol−1.
Option B is almost correct, but the temperature terms 1/298 and 1/308 would need to be swapped to give a positive value for the activation energy.
The question is in the “hard” or “very hard” category since students must be able to identify the correct terms in the question for use in the equation, rearrange the equation correctly, and also perform a unit conversion.

Explanation:
Students should be aware of the definition of frequency factor. However, questions on this topic are somewhat uncommon, and students could confuse this concept with the idea that molecules capable of successful collision lie above Ea in a Boltzmann distribution (leading them to select option D). The difficulty level is therefore at the higher end of the “easy” range.

Explanation:
$)$.
If $\Delta G$ is positive, ln(K) must be negative. ln(K) is negative for values smaller than 1.
A positive $\Delta G$ value indicates that the reaction is not spontaneous. Therefore, the equilibrium concentrations of the reactants are larger than the ones of the products; the equilibrium constant is less than 1.

Explanation:
Using trials 1 and 2, as [X] doubles, rate also doubles therefore first order with respect to [X].
Using trials 2 and 3, as [Y] halves, rate stays the same and so, zero order with respect to [Y].
This gives a slow step that depends on unimolecular X, and not Y.

Explanation:
The balanced chemical equation is 2C3H7OH(l)+9 O2(g)→6 CO2(g)+8 H2O(l). The sum of the coefficients is $25$.

Explanation:
Q>Kc, therefore the backward reaction will be favored as the system approaches dynamic equilibrium.
The backward reaction is endothermic, so the temperature will decrease.
There are more moles of gas on the left and so pressure increases. NO2 is red-brown and so the gas mixture will get darker.

Explanation:
Four factors that can increase the rate of a chemical reaction are: increasing the temperature of the reaction, adding a catalyst, increasing the concentration of the reactants and decreasing the solid particle size of the reactants.

Explanation:
The molecularity is given by the power to which the species is raised to in the rate expression. X is raised to the power of two meaning the rate determining step involves two X molecules.

Explanation:
The rate expression can only be determined experimentally.

Explanation:
D has the steepest gradient when a tangent is drawn.