Rate Of Reaction

Question 1

What is the rate of the reaction?

Answer 1

The speed of a reaction

Question 2

Name examples of chemical reactions and if they are slow or fast

Answer 2

Rusting - slow reaction
Explosion- fast
Weathering- slow
Sodium in water- fast
Rotting fruit - slow

Question 3

Name 5 ways to speed up a reaction

Answer 3

Increase temperature
Increase concentration of a liquid
Increase pressure of gases
Use a catalyst
Increase surface area of solid

Question 4

Describe collision theory/ how you know when a reaction happens

Answer 4

If a reaction happens:
-Particles are constantly moving
-for the collision to be successful the particles must have the right amount of activation energy- The minimum amount of energy required for an effective collision
- more frequent collisions
- then new substances are formed

Question 5

What is the equation for calculating rate of reaction?

Answer 5

Amount of reactant used or amount of product made/ time taken

Question 6

Describe method for required practical- concentration and rate

Answer 6

• make a cross with a board one on piece of paper
• measure 50ml of sodium thiosulfate (40g/dm3) using large measuring cylinder
• put sodium thiosulfate into conical flask
• put conical flask on top of cross
• measure 10ml of hydrochloric acid using small measuring cylinder
• add hydrochloric acid to conical flask and start the stop watch at same time and swirl
• stop stopwatch when cross has completely disappeared
• repeat with different concentrations- 32g/dm3, 24g/dm3, 16g/dm3, 8g/dm3

Question 7

Describe method for required practical- concentration and rate

Answer 7

• make a cross with a board one on piece of paper
• measure 50ml of sodium thiosulfate (40g/dm3) using large measuring cylinder
• put sodium thiosulfate into conical flask
• put conical flask on top of cross
• measure 10ml of hydrochloric acid using small measuring cylinder
• add hydrochloric acid to conical flask and start the stop watch at same time and swirl
• stop stopwatch when cross has completely disappeared
• repeat with different concentrations- 32g/dm3, 24g/dm3, 16g/dm3, 8g/dm3

Question 8

And symbol equation for the required practical- concentration and rate when sodium thiosulfate reacts with hydrochloric acid

Answer 8

Sodium thiosulfate + hydrochloric acid -> sodium chloride + sulfuric acid dioxide + sulfur + water

Na2S2O3 (aq) + 2HCl (aq) -> 2NaCl (aq) + SO2 (g) + S (s) + H2O (l)

Sulfur is a white solid so it turns the solution cloudy

Question 9

What are the variables for required practical concentration and rate?

Answer 9

Independent- concentration of sodium thiosulfate
Dependent- time taken for cross to disappear
Control - volume of sodium thiosulfate
Volume of hydrochloric acid
Same person look for cross disappearing
Concentration of hydrochloric acid

Question 10

Write risk assessment for required practical- concentration and rate

Answer 10

Risk - hydrochloric acid
Hazard - irritate skin
Controlling risk- wash off skin, wear goggles

Risk- glassware
Hazard- cuts
Controlling risk- tell teacher if broken

Risk- sulfur dioxide
Hazard- irritates asthma
Controlling risk - open windows, keep distance

Question 11

What graph do you plot for the required practical ?

Answer 11

Line graph as the independent and dependent variable are continuous

Question 12

Describe method for required practical- temperature and rate

Answer 12

• measure 50cm3 of 1.0M hydrochloric acid using a measuring cylinder. Pour the acid into the 100cm3 conical flask
• fit the bung and delivery tube to the top of the flask
• half fill the trough or bowl with water
• fill other measuring cylinder with water. Make sure it stays filled with water when you invert it into water trough and delivery tube is positioned correctly
• add 1.3cm strip of magnesium ribbon to flask, put bung back as quickly as possible and start stop watch
• record volume of hydrogen gas given off at suitable intervals, continue timing until volume of gas doesn’t change
• repeat steps 1-6 using hydrochloric acid at 40 degrees

Question 13

Write risk assessment for required practical - temperature and rate

Answer 13

Risk- magnesium
Hazard- flammable
Controlling risk- no use if Bunsen burner in experiment

Risk- hydrogen gas
Hazard- flammable
Controlling risk- no use of Bunsen burner

Risk- glassware
Hazard- cuts
Controlling risk- tell teacher

Risk- hydrochloric acid
Hazard- irritates skin
Controlling risk- rinse off
Wear goggles

Question 14

How does increasing temperature effect rate of reaction

Answer 14

• increasing temp causes rate of reaction to increase because particles have more kinetic energy and move faster so there are more frequent collisions
  -also more particles have the activation energy

Question 15

How does increasing the concentration affect the rate of reaction?

Answer 15

Increasing concentration increases rate of reaction because there are more particles so this causes more frequent collisions
(Increasing pressure is the same as increasing concentration)

Question 16

How does increasing surface area effect the rate of reaction ?

Answer 16

Increasing the surface area, increases the rate of reaction
To increase the surface area u need to make the substance smaller (use powdered)
This causes more frequent collisions

Question 17

What are catalysts?

Answer 17

Speed up a reaction but aren’t used up
Only small amounts are needed
Catalysts are specific to a reaction
They aren’t included in the chemical equation

Question 18

How do catalysts affect the rate of reaction?

Answer 18

Increase the rate of reaction by providing a different/ alternating pathway for the reaction that has a lower activation energy

Question 19

Write steps for working out the rate (gradient) of a straight line

Answer 19

1 make a triangle using your line
2 workout change in y axis
3 workout change in x axis
4 workout rate = change in y /change in x

Question 20

Write steps for working out rate of curved line

Answer 20

1 fine the plot on the curve (in the question)
2 draw a straight line that touches the point , and make a triangle
3 workout change in y and x axis
4 workout gradient = change in y / change in x

Question 21

What are reversible reactions?

Answer 21

A reaction that goes both forwards and backwards
The reactants change into products and as soon as some products are made they react to form the reactants

Question 22

Give an example of a reversible reaction and state the forwards and backwards reaction

Answer 22

Heating copper sulfate
Forward= exothermic
Backward = endothermic

Question 23

Write an equation for a reversible reaction

Answer 23

Hydrated copper sulfate (blue) reversible reaction symbol Anhydrous copper sulfate (white) + water

Question 24

When is equilibrium reached?

Answer 24

When the rate of forwards reaction is the same as the rate of backwards reaction in a closed system

Question 25

What does a closed system do?

Answer 25

Stops any reactants or products escaping

Question 26

What conditions when Changed, changed the equilibrium?

Answer 26

Concentration
Pressure
Temperature

Question 27

Explain what happens to the yield when u increase the concentration

Answer 27

1) write rule- if u increase the concentration of the reactant equilibrium will move to the side of the products
2) write which direction equilibrium will move- will move forwards
3) write what happens to the amount of product made - more product is made

Question 28

What happens to the yield when you increase the pressure?

Answer 28

1) workout number of molecules in each side
2) write the rule- if we increase the pressure equilibrium moves to the side with less molecules
3) write which direction the equilibrium will move
4) write what happens to the amount of product made

Question 29

What happens to the yield when we increase the temperature?

Answer 29

1) write on the equation the endothermic and exothermic direction
2) write the rule- when u increase the temp the equilibrium moves in the endothermic direction
3) write which direction the equilibrium will move
4) write what happens to the amount of product made