Chemistry - 2013 E.C (2020/2021) Ethiopian University Entrance Exam (EUEE)

A A positive catalyst decreases the rate of a reaction by increasing the activation energy.

B A catalyst slows down or speeds up a reaction, itself being consumed.

C The role of a catalyst is to increase or decrease the rate of a reaction by lowering or increasing the activation energy.

D A negative catalyst increases the rate of a reaction by decreasing the value of activation energy.

A in the activated complex, the original bonds are weakened and the new bonds are partially formed.

B the collision between two reacting species results in the formation of an activated complex, which has less energy than both the reactants and products.

C the standard reaction enthalpy (ΔH°) depends on the magnitude of the activation energy (Ea).

D the activation energy is the energy that must be absorbed or released by reactants to reach the activated complex.

A The value of a rate constant tells us how fast or slow a reaction is.

B It expresses the relationship between the rate of a chemical reaction and the volume of reacting species.

C A small rate constant indicates a faster reaction and a larger rate indicates a slower reaction.

D The value of a rate constant is independent of reaction conditions.

A for a given value of activation energy the value of the rate constant increases as the temperature increases.

B reactions with larger activation energies have higher values of k and are therefore faster.

C for a given value of activation energy, the value of the rate constant decreases as the temperature increases.

D reactions with larger activation energies, the value of the rate constant decreases as the temperature increases.

A different number of neutrons and same number of protons.

B the same number of electrons and neutrons.

C the same atomic mass but different atomic numbers.

D different physical and chemical properties.

A 4hr

B 1hr

C 3hr

D 5hr

A 107.94 amu

B 108.9 amu

C 107.86 amu

D 107.4 amu

A A particle with a mass moving at a given speed can be described by the wave characteristic of material particles.

B If we measure the momentum of a particle precisely then its position will be correspondingly precise.

C Both the location and the momentum of a subatomic particle like the electron cannot be precisely known.

D A small particle like the reaction can behave both as a particle and a wave.

A accepts a H+ ion.

B dissociates in water to yield H3O+.

C accepts a pair of electrons.

D donates an OH- ion.

A it can accept a proton from an acid and donate a proton to a base.

B it has a very high ionic product, Kw.

C it acts both as Bronsted-Lowry and base.

D it undergoes a reversible dissociation with a very low ionic product, Kw.