Rate of reaction

Which change in conditions in the Haber process results in a decrease in activation energy?

• increasing the concentration of the reactants

• increasing the pressure

• increasing the temperature

• using a catalyst

Which change will increase the speed of the reaction between 1 mol of each of two gases?

• a decrease in surface area of the catalyst

• a decrease in temperature

• a decrease in the volume of the reaction flask

• an increase in the volume of the reaction flask

Dilute sulfuric acid reacts with copper(II) oxide to form copper(II) sulfate and water.

What would not alter the rate of this reaction?

• the concentration of the sulfuric acid

• the pressure t which the reaction takes place

• the size of the particles of copper(II) oxide

• the temperature of the reacting mixture

In which reaction is the pressure least likely to affect the rate of reaction?

• C(s) + CO₂(g) → 2CO(g)

• 2SO₂(g) + O₂(g) → 2SO₃(g)

• N₂(g) + 3H₂(g) → 2NH₃(g)

• NaOH(aq) + HCI(aq) → NaCI(aq) + H₂O(ℓ)

Magnesium reacts with hydrochloric acid.

Which solution would give the fastest initial rate of reaction?

• 40 g of HCI 1000cm³ of water

• 20 g of HCI in 1000cm³ of water

• 10 g of HCI in 100cm³ of water

• 4 g of HCI in 50cm³ of water

Which factor decreases the activation energy of a reaction?

• addition of catalyst

• increase in concentration of the reactants

• increase in pressure

• increase in temperature

Which of the following statements best explains why coal dust forms an explosive mixture with air?

• Powdering coal catalyses the explosion.

• Powdering col releases hydrogen from compounds in coal.

• Powdering coal releases methane from compounds in coal.

• Powdering coal produces a large surface area.

If a strip of magnesium is dropped into excess hydrochloric acid an exothermic reaction occurs.

Why does the rate of this reaction increase during the first few seconds?

• The amount of magnesium is decreasing.

• The magnesium is acting as a catalyst.

• The solution is becoming hotter.

• The surface area of the magnesium is increasing.

When an excess of calcium carbonate is added to dilute hydrochloric acid, the reaction gradually becomes slower and finally stops.

Which statement best explains why this happens?

• An insoluble layer of calcium chloride is formed on the calcium carbonate.

• The pieces of calcium ocarbonate gradually become smaller.

• The calcium calbonate is covered by bubbles of carbon dioxide.

• The concentration of hydrochloric acid gradually reduces to zero.

In each of five different experiments the same mass of of magnesium reacts with the same volume of an excess of sulfuric acid. Which set of conditions will results in the magnesium being used up the fastest?

• A

• B

• C

• D