The Rate And Extent Of Chemical Change

Question 1

What is a rate of reaction

Answer 1

How fast the reactants are changed into products

Question 2

Example of slow rate of reaction

Answer 2

-rusting of iron
-chemical weathering

Question 3

Example of moderate speed reaction

Answer 3

-magnesium reacting with an acid to produce a gentle stream of bubbles

Question 4

Example of fast rate of reaction

Answer 4

-burning
-explosions

Question 5

How graphs show rate of reaction

Answer 5

-steep line=fast rate
-flat line=reaction finished
-short steep line is faster
-long steep line means more reactants

Question 6

What is collision frequency and how does it affect rate

Answer 6

-how often particles collide
-the more collisions, the faster the reaction

Question 7

4 things that the rate of reaction depends on

Answer 7

1. Temperature
2. Concentration of solution or pressure of gas
3. Surface area
4. Presence of a catalyst

Question 8

How does increasing temperature affect rate

Answer 8

-when temp is increased, the particles move faster
-if they move faster, they collide more frequently
-more faster=more energy=enough energy for reaction to happen

Question 9

How does increasing concentration affect rate

Answer 9

-more concentrate= more particles colliding in same volume
-if pressure if gas is increased = same number of particles colliding in smaller space
-more collisions

Question 10

How does increasing surface area affect rate of reaction

Answer 10

-if one reactant is solid, breaking it into smaller pieces will increase its surface area it volume ratio
-same volume of solid=particles will have more area to work on=more collisions

Question 11

How does using a catalyst increase the rate of reaction

Answer 11

-catalyst is a substance that speeds up a reaction without being used up in the reaction itself
-they work by decreasing the activation energy
-less energy needed for reaction to occur

Question 12

Formula for rate of reaction

Answer 12

Rate of reaction= amount of reaction used or amount of product formed / time

Question 13

How to see rate of reaction visually

Answer 13

-if initial solution is transparent and the product is a precipitate which clouds the solution
-you can observe a mark at the bottom of a flask and see how long it takes for the mark to disappear, the faster it disappears, the quicker the reaction
-you can’t plot a reaction graph from these results

Question 14

Seeing a rate if reaction by change in mass

Answer 14

-measuring the speed of reaction that produces a gas using a mass balance
-as gas is released, the mass will decrease
-the quicker the mass drops, the quicker the reaction
-if you take measurements at regular intervals, you can plot rate if reaction and find rate easily
-this is the most accurate

Question 15

Seeing rate of reaction based off volume of gas given off

Answer 15

-uses a gas syringe to measure gas given off
-more gas given off in a given time interval, the faster the reaction

Question 16

Magnesium and HCL reaction experiment

Answer 16

1. Add set volume of dilute HCL to conical flask and place on mass balance
2. Add magnesium ribbon to acid and quickly plug the flask with cotton wool
3. Start stopwatch and record mass on balance at regular intervals
4. Plot graph to get rate of reaction used or

Question 17

Sodium Thiosulfate and HCL reaction experiment

Answer 17

1. They’re both clear solutions but they react together to produce a yellow precipitate of sulfur
2. Add a set volume of dilute sodium thiosulfate to conical flask
3. Place flask on piece of paper with black cross on it
4. Add dilute HCL to flask and start a stopwatch
5. Time how long it takes for black cross to disappear
6. The shorter the time, the faster the reaction
7. The higher the concentration, the quicker the reaction

Question 18

How to find mean rate of reaction

Answer 18

Change in y / total time taken for the reaction

Question 19

How to find rate of reaction at a specific point

Answer 19

Find gradient of tangent at that point