Topic 6-Rate And Extent Of Chemical Change

Front 1

Describe the what happens in the quantity of product formed over time graph

Back 1

At the start the line is steep= fast reaction is taking place. Lot of reactant molecules are reacting and forming into product. The slope then gradually gets less steep due to the reaction slowing down. This is because most of the reactant molecules have turned into product. The line then becomes flat which indicates that the reaction has stopped (all of the reactant has turned into product)p.s gas is measured in cm3

Hint 1

Reactant>product

Front 2

What is the formula to find out the mean rate of reaction?

Back 2

Quantity of product formed/time taken

Front 3

30 grams of reactant was used in 10 seconds calculate the mean rate of reaction

Back 3

30/10= mean rate of reaction: 3g/s

Front 4

What is a tangent and what can it be used for

Back 4

A tangent is a straight line that touches a curve and it's used for measuring the rate of a reaction

Front 5

How do you use the tangent to measure the rate of reaction at a specific point?

Back 5

Firstly draw your tangent. Then construct a triangle from it. Then find the length (X axis) and width(y axis) of the triangle (in grams) then divide the y axis by the X axis.

Hint 5

Straight line

Front 6

What is collision theory

Back 6

Collision theory States that in order for a chemical reaction to occur, the reacting particles must collide with each other. These collisions must have sufficient energy. The rate of reaction is determined by the frequency of collisions per second(number collisions per second)

Front 7

What is the relation between concentration and rate of reaction?

Back 7

As the concentration increases so does the rate of reaction.which means that the concentration is proportional to the rate of reaction.

Front 8

How to carry out the disappearing cross reaction

Back 8

Sodium thiosulfate+hydrochloric acid makes sulfur which can make a solution cloudy. In this reaction, one of the products is sulfur.

Firstly, put 10cm3 sodium thiosulfate and 10cm3 of hydrochloric acid solution into a conical flask and put a printed black cross underneath. Swirl the solution and start the timer. After some time the solution will turn cloudy. You then stop the timer when you can no longer see the cross. Repeat the experiment with lower concentrations of sodium thiosulfate solution. After completing the experiment , calculate the mean values for each concentration of sodium thiosulfate. Don't include any anomalous results when calculating the mean.

Hint 8

Cloudy solution

Front 9

What are the negatives of the disappearing cross experiment

Back 9

Everyone has different eyesight so one person may see the cross for a longer period of time than someone with bad eyesight. This can be resolved however by using a larger cross.

Front 10

How do you carry out the hydrogen gas experiment

Back 10

Magnesium+hydrochloric acid makes magnesium chloride+hydrogen. This hydrogen gas allows us to measure the volume of hydrogen of gas produced.

Firstly put 50cm3 hydrochloric acid into a conical flask then attach the flask to a bung and delivery tube. Then place delivery tube into container filled with water. Then place a measuring cylinder over the delivery tube. Add a 3 cm strip of magnesium to the hydrochloric acid and start the timer. The reaction produces hydrogen gas (which is trapped in measuring cylinder).Every 10secs measure the volume of hydrogen gas in the measuring cylinder until no gas is given off. Repeat the experiment using different concentrations of hydrochloric acid.

Front 11

What do both the disappearing cross and the hydrogen gas experiment show?

Back 11

They show that the greater the concentration the faster the reaction.

Front 12

What is the relation between the surface area and rate of reaction

Back 12

The rate increases when we increase the surface area of a solid.

Front 13

What is surface area to volume ratio?

Back 13

Smaller sized blocks have a larger surface area to volume ratio than larger blocks. This means that they have more particles on the surface which means more collisions per second. This increases the rate of reaction.

Front 14

What is the investigation of surface area to volume ratio

Back 14

Firstly put hydrochloric acid and calcium carbonate in a conical flask and put a marble chip in it And attach it to a bung and delivery tube (tube should be in container filled with water with a measuring cylinder on top.) The reaction should produce carbon dioxide gas. Repeat the experiment by putting more marble chips at a smaller size in the test tube . It can be hard to measure the hydrogen gas due to how rapid it is.

Front 15

What is the alternative investigation to the surface area to volume ratio experiment

Back 15

Place a conical flask containing hydrochloric acid with a marble chip inside and put it in top of a balance. Some of the mass is lost due to carbon dioxide escaping which can help us determine the rate of reaction. Putting cotton wool on top of the conical flask prevents acid from escaping. If it did escape, then we would get an anomalous result. However carbon dioxide can still escape through the cotton wool.

Front 16

What is activation energy?

Back 16

Is the minimum amount of energy required for particles to collide/react successfully

Front 17

What is the relation between temperature and rate of reaction?

Back 17

Increasing the rate of reaction increases the energy in particles. This makes the particles move faster which means more collisions.This means that more particles can overcome the activation energy barrier by colliding successfully. Which increases the rate of reaction.

Front 18

Why are catalysts useful

Back 18

They can speed up reactions at a low temperature which uses less energy and saves money.

Front 19

How do catalysts work?

Back 19

They increase the rate of reaction by choosing a different pathway for the reaction that has a lower activation energy. This means when a catalyst is present, the particles require less energy to cross the activation barrier.

Front 20

State a key fact about energy in reversible reactions

Back 20

If a reversible reaction is endothermic in one direction, then it's exothermic in the opposite direction.

Front 21

What is equilibrium

Back 21

It's when the forward and reverse reactions take place at the same rate

Front 22

What is Le chateliers principle?

Back 22

Le chateliers principle states that if you change the conditions of the reversible reaction at equilibrium then the system will counteract that change.