Rates of Reaction

Question 1

What is the rate of reaction equation? What are the units?

Answer 1

Rate = 1/time. Units = s to the -1.

Question 2

What are the 2 ways of finding out the rate of a reaction?

Answer 2

Measure how quickly one of the reactants has been used up over time or measure how quickly one of the products forms over time.

Question 3

What is the word and symbol equation for the reaction of marble chips (calcium carbonate) with hydrochloric acid?

Answer 3

Calcium carbonate + hydrochloric acid —> calcium chloride + water + carbon dioxide
CaCO3 + 2HCl —> CaCl2 + H2O +CO2

Question 4

What is the word and symbol equation for the reaction of metals with dilute acid?

Answer 4

Magnesium + hydrochloric acid —> magnesium chloride + hydrogen
Mg + 2HCL —> MgCl2 +H2

Question 5

What catalyst is added to hydrogen peroxide?

Answer 5

Manganese (IV) oxide catalyst.

Question 6

What happens when manganese (IV) oxide is added to hydrogen peroxide? What is that symbol equation?

Answer 6

The hydrogen peroxide quickly decomposes to form water and oxygen gas.
2H202 —> 2H2O + O2

Question 7

What does sodium thiosulfate react with? What is formed? What can be measured here?

Answer 7

Sodium thiosulfate reacts with an acid to form the precipitate of sulfur. The time taken to form a certain amount of precipitate can be measured.

Question 8

What are the two ways to measure the rate at which a gas forms?

Answer 8

Measure the volume of gas produced per unit time (GAS SYRINGE) or measure the loss in mass in a given time.

Question 9

Finish the sentence: The steeper the slope…?

Answer 9

The faster the rate of reaction.

Question 10

When measuring the volume of gas produced per unit time (GAS SYRINGE), how do we know when the reaction is over? What will this look like on a graph?

Answer 10

When no more carbon dioxide is produced and when the graph’s curve is flat.

Question 11

When measuring the loss of gas in a given time, why do we use a plug of cotton wool? What does this ensure?

Answer 11

To stop any of the acid from splashing out of the flask and there’s ensure that hydrogen is the only thing that can escape.

Question 12

When measuring the loss of mass in a given time, what effect does the hydrogen have of escaping from the flask into its surroundings?

Answer 12

This causes the mass in the flask to decrease.

Question 13

Wen measuring the loss in mass in a given time, how do we know when the reaction is over? What does this mean for the mass of the flask and for a graph?

Answer 13

When no more hydrogen is produced. If no more hydrogen is leaving the flask, the mass will not change and the curve will become flat.

Question 14

What does collision theory state?

Answer 14

For a reaction to occur, particles must collide.

Question 15

What is the activation energy?

Answer 15

The minimum energy needed for the reaction to occur.

Question 16

What are the four factors that can affect the rate of reaction?

Answer 16

1. Temperature
2. Concentration of a solution
3. Surface area of solid reactants
4. The presence of a catalyst

Question 17

Explain how increasing the temperature will increase the rate of reaction:

Answer 17

-The particles will have more energy and will move faster
-There will be more collisions in a given time and more of the collisions will have the activation energy required fora reaction to occur
-There will be more successful collisions in a given period of time so the rate of reaction will increase.

Question 18

Explain how increasing the concentration of a solution increases the rate of reaction:

Answer 18

-There are more particles in the same volume of solution
-This leds to more collisions between particles meaning there will be more successful collisions in a given period of time
-Therefore a faster rate.

Question 19

Explain how increasing the surface area by breaking a solid reactant into small pieces increases the rate of reaction:

Answer 19

-There are more particles on the surface exposed to the other reactant
-There are more collision, leading to more successful collisions with the activation energy between the particles in a given time
-So, the reaction rate is faster.

Question 20

WHAT is a catalyst?

Answer 20

A substance which increases the rate of a reaction without being used up.

Question 21

How does a catalyst work?

Answer 21

It acts by providing an alternative pathway of lower activation energy.

Question 22

What happens if the new reaction pathway has a lower activation energy?

Answer 22

Then more of the collisions will have sufficient energy to be successful in a given period of time which means the rate will be faster.

Question 23

What type of metals are the best catalysts?

Answer 23

Transition metals.