Speeds of Reactions

Which energy profile diagram shows the slowest endothermic reaction?

• A

• B

• C

• D

Tags

NGSS.HS-PS1-4

Reaction 1: 10 g of magnesium ribbon with excess 2.0 mol/dm³ hydrochloric acid

Reaction 2: 5 g of magnesium powder with excess 2.0 mol/dm³ hydrochloric acid

In both experiments, the volume of hydrogen produced, V, is measured against time, t, and the results plotted graphically. Which set of graphs is correct?

• A

• B

• C

• D

Tags

NGSS.HS-PS1-5

Aqueous hydrogen peroxide decomposes according to the equation:

2H₂O₂(aq) → 2H₂O(l) + O₂(g)

When manganese(IV) oxide is added to an aqueous solution of hydrogen peroxide, the speed of decomposition increases because

• the kinetic energy of the hydrogen peroxide molecules increases.

• the reaction becomes more exothermic.

• the hydrogen peroxide molecules collide more frequently.

• the minimum amount of energy which hydrogen peroxide molecules must possess in order to react decreases.

Tags

NGSS.HS-PS1-5

The graph shows a curve S which was obtained from the reaction between excess potassium carbonate and 50 cm³ of 1 mol/dm³ of sulfuric acid carried out at room temperature.

What change to the experiment will not result in curve T?

• add 50 cm³ of water to the acid

• use bigger lumps of potassium carbonate

• use 50 cm³ of 0.75 mol/dm³ sulfuric acid

• use 100 cm³ of 1 mol/dm³ nitric acid

Tags

NGSS.HS-PS1-5

What happens to the height of the peak (P) and the activation energy (E_a) when the temperature of the mixture increases?

• P: decreases ; E_a : Moves to the left

• P: decreases ; E_a : Moves to the right

• P: decreases ; E_a : Does not change

• P: increases ; E_a : Moves to the left

Tags

NGSS.HS-PS1-5

Which acid solution, when added to 5 g of zinc granules, would have the highest initial rate of reaction?

• 25 cm³ of 1.00 mol/dm³ sulfuric acid

• 25 cm³ of 0.200 mol/dm³ hydrochloric acid

• 50 cm³ of 1.00 mol/dm³ hydrochloric acid

• 100 cm³ of 0.100 mol/dm³ sulfuric acid

Tags

NGSS.HS-PS1-5