Rate of reaction

Question 1

Rate of reaction equation

Answer 1

rate or reaction=amount of reactant used OR product formed/time taken

Question 2

Measuring the amount of reactant used

Answer 2

Units for rate of reaction is g/s or mol
concentration of the reactant=amount (mol)/volume of the reaction mixture (dm3) UNITS ARE MOL/DM3
As the reaction takes place the reactant is being used up
so the reactant decreases
If the product is gas measure the mass in grams

Question 3

Amount of product formed

Answer 3

Amount of product is formed=total volume of gas produced(cm3)/time taken for the reaction to happen
UNITS ARE CM3/S

Question 4

Measuring the time it takes for a reaction mixture to become opaque or change colour

Answer 4

Rate of reaction=1/time taken for solution to change colour

Question 5

Collison theory

Answer 5

Chemical reactions can only take place when the reacting particles collide with each other. The collisions must have sufficient energy. Minimum amount of energy required to cause a reaction is called activation energy
There are four factors that affect the rate of reaction
TEMPRETURE
CONCENTRATION
CATALYST
SURFACE AREA

Question 6

Concentration

Answer 6

high conc, increases the number of particles in the same volume
Increasing pressure of reacting gases increases frequency of collisions and same number of particles are now in a smaller space

If the conc is increased it will decrease the amount
if it decreases it will increase the amount

Question 7

Temperature

Answer 7

In a hot reaction the particles move more quickly, they collide more often with greater energy so more successful collisions.

Question 8

Surface Area

Answer 8

When a solid is grinded it has a larger surface area
More particles are exposed and available for collisions so there are more collisions and a faster reaction
The particles in a solution can only react with particles on the surface of the area

Question 9

Catalyst

Answer 9

Reduces amount of energy needed for a successful collision

speeds up a reaction
provides a surface area for the molecules to attach which increases their chances of bumping in to each other

Speeds up both the forward and reverse reaction

Question 10

reversible reaction

Answer 10

product can react to produce the original reactant
exothermic in one direction and endothermic in the opposite direction
Same amount of energy is transferred

Question 11

closed systems

Answer 11

No reactant are added and no products are removed
When a reversible reaction occurs in a closed system an equilibrium is achieved when the rate of the forward reaction is equal to the rate of the backward reaction.

Question 12

Le chateliers’s principle

EXOTHERMIC REACTION

Answer 12

Decreasing temp will shift equilibrium in the exothermic direction
EXOTHERMIC REACTION
temp raised ,yield decrease’s
temp lowers, yield increase’s

Question 13

Le chateliers’s Principle

ENDOTHERMIC REACTION

Answer 13

Increasing temperature will shift equilibrium in the endothermic direction
ENDOTHERMIC REACTION
Temp raised, Yield increases
Temp lowers, yield decreases

Question 14

Le chateliers’s Principle

PRESSURE

Answer 14

PRESSURE
Increase pressure causes the equilibrium positions to shift to the side with fewer molecules of gas. Yield decrease
Decrease pressure causes the equilibrium position to shift to the side with more molecules of gas. yield increases

Highest-lowest moles

Question 15

Le chateliers’s Principle

REACTANTS

Answer 15

Remove reactants-move to rate reactant

Add reactant-move to make product

Question 16

Le chateliers principle

Answer 16

A reaction in equilibrium will move in the direction to oppose change.

Question 17

Graphs

Answer 17

steeper the line faster the reaction

When one of the reactant is used up the reaction stops

Question 18

Investigate how changes in concentration affect the rates of reactions by monitoring a change in colour or
turbidity

Answer 18

40 g/dm3 sodium thiosulfate solution
• 1.0 mol/dm3 dilute hydrochloric acid
• a conical flask (100 cm3)
• a printed black paper cross
• a stop clock.

1) Use a measuring cylinder to put 10cm3 of sodium thiosulfate solution into a conical flask and place it on a printed black cross
2) Then add 10cm3 of hydrochloric acid into the conical flask
3) Swirl the solution and start the stopwatch and look down through the top of the flask after a certain time the solution will turn cloudy and stop the clock when you can no longer see the cross
4) Carry out the experiment again using a lower conc of sodium thiosulfate solution
5) Repeat the whole experiment and cal mean value for each conc of sodium thiosulfate

PROBLEM
Because everyone has different eyesight some may be able to see the cross for longer but if you all have the same printed cross it should be fine

IV-conc of the acid
DV-How long it takes for the cross to disappear
CV-volume of acid and conc and volume of sodium thiosulfate

Question 19

Investigate how changes in concentration affect the rates of reactions by both
measuring the volume of a gas produced

Answer 19

magnesium ribbon cut into 3 cm lengths
• dilute hydrochloric acid, 1.0 mol/dm3 and 1.5 mol/dm3
• safety goggles
• conical flask (100 cm3)
• single-holed rubber bung and delivery tube to fit conical flask
• water trough
• two measuring cylinders (100 cm3)
• clamp stand, boss and clamp
• stop clock.

1) Use a measuring cylinder to place 50cm3 of hydrochloric acid into a conical flask
2) Attach the conical flask to a bung and delivery tube
3) Place the delivery tube into a container filled with water
4) Place an upturned measuring cylinder also filled with water over the delivery tube
5) Then add a 3cm strip of Mg to hydrochloric acid and start the stop watch
6) Every 10 seconds measure the volume of hydrogen gas in the measuring cylinder continue until no more hydrogen is given off
7) Repeat the experiment using diff conc of hydrochloric acid

IV-
DV-amount of hydrogen being produced
CV-Amount of hydrochloric acid