Rates of Reaction

Question 1

Steep stope means?

Answer 1

Fast reaction

Question 2

Mean rate of reaction formula

Answer 2

quantity of product formed / time taken

Question 3

What is collision theory?

Answer 3

chemical reactions can only take place when the reacting particles collide with each other. collisions must have sufficient energy

Question 4

RP 5 Rates of reaction

RP 5 Disappearing cross reaction, effect of conc

Answer 4

1. Measuring cylinder to put 10cm3 of sodium thiosulfate solution to conical flask
2. Place conical flask onto printed black cross
3. Add 10cm3 HCL to conical flask
4. Swirl solution and start stopwatch
5. Look down through top of flask
6. Solution will turn cloudy and wont see the cross
7. Repeat with low conc sodium thiosulfate solution
8. Repeat whole and calc mean values for each conc of sodium thiosulfate solution

Question 5

rp 5 disappearing cross

sodium thiosulfate solution + Hcl

Answer 5

sulfure (solid) - makes solution go cloudy (causes turbidity)

Question 6

What is reproducibility

Answer 6

• Can be repeated by antoher using a diff technique or equipment
• Same result

Question 7

Prob with disappearing cross experiment

Answer 7

• diff ppl have diff eyesights = some ppl can see cross for longer = diff results
• HOWEVER, cross is same size so prob not too great

Question 8

RP 5

How to measure vol of a gas produced by a reaction

Answer 8

1. Use measuring cylinder to place 50cm3 HCl into conical flask
2. Attach conical flask to bung and delivery tube
3. Place delivery tube into container filled with water
4. upturned measuring cyclidner filled with water over delivery tube
5. Add 3cm strip of MG to HCL and start stopwatch
6. Hydrogen gas produced and thats trapped in MC
7. Every 10s, measure vol of H gas until reaction over
8. Repeat with diff conc of HCL

Question 9

rp 5 measure gas

magnesium + hcl

Answer 9

hydrogen + magnesium chloride

Question 10

Greater conc means?

Answer 10

faster reaction

Question 11

larger surface area means?

Answer 11

faster reaction

Question 12

What causes a reaction to become faster?

Answer 12

• larger sa
• higher conc of a chemical
• higher temp
• catalyst

Question 13

What does cotton wool on a conical flask do?

Answer 13

• allows carbon dioxide to escape
• prevents acid from splashing out of flask

Question 14

Activation energy

Answer 14

min aount of energy that particles must have in order to react collide successfully

Question 15

Why does increasing temp increase rate of reaction?

Answer 15

• increase energy of particles
• move faster
• increases freq of collisions
• each collision has more energy
• can overcome avtivation energy needed

Question 16

Catalyst

Answer 16

increase rate of chemical reactions but arent used up during reaction

Question 17

why are catalysts important?

Answer 17

• allows us to carry out reactions quickly without needing to increase temp
• saves money
• resuable

Question 18

how do catalysts work

Answer 18

• provides a diff pathway for reaction that has a lower activation energy

Question 19

What is produced when you heat hydrated copper sulfate (blue)? What type of reaction is it? What type of reaction is the reversible reaction?

Answer 19

• anhydrous copper sulfate (white) + water
• ENDOTHERMIC
• If you add water to anhydrous copper sulfate, reaction reverses, energy released, hot, EXOTHERMIC

Question 20

What is equilibrium?

Answer 20

forward and reverse reactions will take place at the same rate in a sealed container

Question 21

Le Chateliers Princple

Answer 21

If a system is at equilibrium, and a change is made to the conditions, then the system reponds to counteract the change

Question 22

Where does equilibrium only happen in?

Answer 22

in a closed system

Question 23

Where does equilibrium lie when the conc of the products are higher?

Answer 23

To the right

Question 24

exothermic
endothermic
arrows

Answer 24

exo = right
endo = left

Question 25

What happens to the temp of a system during an exothermic reaction?

Answer 25

increases

Question 26

What does the pressure of a gas depend on?

Answer 26

the number of molcules

Question 27

What happens if you increase pressure on a reversible reaction at equilibrium

Answer 27

position of equilibrium shifts to the side with **small number of molecules**

Question 28

What happens if you decrease pressure on a reversible reaction at equilibrium

Answer 28

position of equilibrium shifts to the side with **larger number of molecules**

Question 29

What 3 things can cause the equilibrium to change?

Answer 29

Temp, pressure and concentration

Question 30

Chatliers = Increasing the conc of reactants will shift equilibrium to what side?

Answer 30

Right - making more products

Question 31

Chatliers = Increasing conc of products will shift equilibrium to which side?

Answer 31

left - making more reactants

Question 32

If the forward reaction is exo (releases heat) 1. What happens to equillibrium if you increase the temp? 2. Decreasing temp?

Answer 32

* Increase temp = left (endo direction) * Decreasing = right (eco direction)

Question 33

If the forward reaction is endo (absorbs heat) 1. What happens to equillibrium if you increase the temp? 2. Decreasing temp?

Answer 33

* Increase temp = right * Decrease = left

Question 34

Chatliers 1. Increasing pressure shifts equilibrium to what side? 2. Decreasing pressure?

Answer 34

* Increase = fewer gas molecules * Decreasing = more gas molecules

Question 35

Do catalysts have an affect on equilibrium?

Answer 35

No, they only speed up the rate at which equilibrium is reached

Question 36

Delta H 1. Negative 2. Positive

Answer 36

* negative eg -38 = exothermic, releases 38 kJ of energy per mole of reactant - temp of surroundings increase * positive - endo

Question 37

What caused cloudyness in sodium thiosulfate and Hcl reaction? and why

Answer 37

Sulfur because its a precipitate

Question 38

How does a catalyst help in the Haber process?

Answer 38

reduce energy costs