Kinetics practice 3

Excess magnesium powder was added to a beaker containing hydrochloric acid, HCl (aq).

The mass of the beaker and its contents was recorded and plotted against time (line I).

Which change could give line II?

• Doubling the mass of powdered Mg

• Using the same mass of Mg ribbon

• Increasing the temperature

• Using the same volume of more concentrated HCl

Tags

NGSS.HS-PS1-5

Copper catalyses the reaction between zinc and dilute sulfuric acid.

Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g)

Why does copper affect the reaction?

• Decreases the activation energy

• Increases the activation energy

• Increases the enthalpy change

• Decreases the enthalpy change

Tags

NGSS.HS-PS1-4

Which quantity can be changed by the use of a catalyst?

• I and II only

• I and III only

• II and III only

• I, II and III

Why does the rate of a reaction increase when the temperature is increased?

I. The activation energy decreases.

II. There are more particles with energy equal to or greater than the activation energy.

III. The frequency of collisions between particles increases.

• I and II only

• I and III only

• II and III only

• I, II and III

The diagram represents the Maxwell‒Boltzmann energy distribution curve of the reactants for a chemical reaction with different activation energies, E_a1 and E_a2.

What is the reason why the rate of the reaction with activation energy E_a2 is greater?

• More frequent collisions between the particles occur.

• More energetic collisions between the particles occur.

• A catalyst has been added.

• The temperature is higher.

Tags

NGSS.HS-PS1-5

Which change increases the rate of a chemical reaction?

• Increasing the size of solid reactant particles

• Decreasing the concentration of aqueous reactants

• Increasing the surface area of a solid reactant

• Decreasing the pressure of gaseous reactants

Which is not affected by an increase in temperature?

• Rate of reaction

• Collision frequency

• Collision geometry

• % of molecules with E ≥ E_a

Tags

NGSS.HS-PS1-5

Which graph best represents the relationship between the average kinetic energy of molecules of a gas and temperature in K?

• A

• B

• C

• D

In which flask will the reaction between 2.0 g of magnesium carbonate and 25 mL 1.0 mol L^–1 hydrochloric acid occur most rapidly?

• A

• B

• C

• D

Tags

NGSS.HS-PS1-5

Consider the reaction between gaseous iodine and gaseous hydrogen.

I₂(g) + H₂(g) ⇄ 2 HI(g) ΔH^∅=-9 kJ

Why do some collisions between iodine and hydrogen not result in the formation of the product?

• The I₂ and H₂ molecules do not have sufficient energy.

• The system is in equilibrium.

• The temperature of the system is too high.

• The activation energy for this reaction is very low.

Tags

NGSS.HS-PS1-4