Spreadsheet - Rate Of Reaction - Concentration Effect

Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 EFFECT OF CONCENTRATION ON THE RATE OF REACTION Teacher’s Guide / Chemistry Form 5 / Spreadsheet

SCIENTIFIC CONCEPT Chemistry reactions occur when substances react with one another. How active of one chemistry reactions is known as rate of reaction. When reaction occur, reactant will decrease and the product will increase as the time pass away. So, the rate of reaction can be determined with the measurement rate of loosing reactant or rate of products form. Rate of reaction can be determined as the changing of substance quantity with time. For a reaction produce gas, rate of reaction is measured from the volume gas released per unit time. The rate of reaction will increase when the concentration of the reactant increase. No. experiment Volume of Sodium

1 45

2 35

3 25

4 15

5 5

Thiosulfate, V1 (cm3) Volume of water (cm3) Volume of Sulfuric

0 5

10 5

20 5

30 5

40 5

acid (cm3) Total Volume (cm3) Time taken for ‘X’ to

50 24

50 32

50 44

50 68

50 130

0.0417

0.0313

0.0227

0.0147

0.0077

disappear, t (s) 1/Time, 1/t (s-1)

We use the knowledge / concept of concentration for our benefit.

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 UNIQUE FEATURE OF THIS ACTIVITY This activity needs the students to determine and understand the rate of reaction. The unique features of this spreadsheet are: i.

The changing of environment of reactant or product will resulting different rate of reactions.

ii.

Concentration of the reaction can manipulate the resulting data.

iii.

Controlling the variables to get such result by relating it with time.

iv.

The changing of concentration of the substance in chemistry reaction will resulting a few different time for time taken for ‘X’ symbol to disappear.

v.

The ability of spreadsheet to show the data taken from experiment and view it in simple form and easy to produce and process the data.

vi.

Allow the students to explore some kind of visualizing important data in digital graphic form like graph that generate by spreadsheet data like Microsoft Excel.

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 ENGAGE THE

MAGICAL OF COLOUR

Figure 1

There are 5 glasses with same solution but different in composition. The colour of the solution is green, from light green to dark green. •

What is the density of light from left solution to the right solution?

•

Why the solution is different in density of colour even the volume of the solution is same?

•

How could this happen?

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 EMPOWER Steps 1. Students are briefly given information about the rate of reaction. About its meaning and application in daily life. 2. Students are knows the rate of reaction is including with time. 3. Students are given -

Measuring cylinder

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Stop watch

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Conical flask

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White paper with marked “X” at the center

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Sodium Thiosulphate

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Hydrochloric acid

4. Students are thinking about the relationship of the reaction between sodium thiosulphate with hydrochloric acid and relating it with the measure of time. 5. Students need to plan an experiment by using the given apparatus and chemicals to determine the effect of concentration on the rate of reaction. 6. Students have to construct a hypothesis for the relationship of the concentration of substance and the rate of reaction. 7. Students should know the effect on varying concentration of sodium thiosulphate on the rate

of reaction. 8. Help students to determine the data needed by using appropriate scientific experimental procedures. 9. The instructions given to start the activity may be as given below: -

Open spreadsheet file

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Name the file as ‘Concentration factor affecting rate of reaction’

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Measuring 45cm3 sodium thiosulphate 0.2M and put into conical flask.

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The conical flask is put on the white paper with marked “X” at the center.

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 -

By using 10 cm3, 5 ml sulphuric acid is measured and put into the conical flask. At the same time, stop watch begin.

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Swirl the conical flask. Precipitation of yellow solution is appeared slowly. Marked ‘X’ is observed perpendicularly from the top of the conical flask through the solution.

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The time taken for the marked ‘X’ disappear is recorded by stopping the stop watch.

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The time taken is recorded in the column C8 of your spreadsheet.

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Repeat step by reducing the concentration of sodium thiosulphate by diluting with distilled water but fix the total volume and the record in the next column, C8, D8, E8, F8, and G8.

How to set up your spreadsheet: 1. Click on cell C7, enter formula =C4*(C5/(C5+C6)) to find the concentration for the sodium

thiosulphate solution used. 2. Copy cell C7, then paste it into cell D7 or click cell C7 then drag it to the next columns (to determine the concentration for the sodium thiosulphate solution with different amount volume in dilution with water). 3. Click cell C11, type =1/C10 to determine the rate of reaction. Drag the cell C11 to the next

column. Rate of reaction for each repeating experiment will appear. How to draw a graph with your spreadsheet: 1. Graph Concentration of Sodium Thiosulphate against Time i.

Highlight cells B7 to G7

ii.

Hold down the button CTRL

iii.

Highlight cells B10 to G10

iv.

Get Insert > Graph

v.

Rewrite the title for each axis and give title for the graph.

2. Graph Concentration of Sodium Thiosulphate against 1/Time i.

Highlight cells B7 to G7

ii.

Hold down the button CTRL

iii.

Highlight cells B11 to G11 5

Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 iv.

Get Insert > Graph

v.

Rewrite the title for each axis and give title for the graph.

vi.

Select Design>Move Chart>Object In: Sheet 2

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 Results

Figure 2

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009

Figure 3

QUESTIONS: 1. In this experiment, a few types of concentration of the sodium thiosulphate are use to

determine the rate of reaction. How can we differentiate the concentration of sodium thiosulphate from basic solution of 0.2 mol dm-3? 2. From the graph of the concentration against time (Figure 2), how can we get the rate of

reaction at instantaneous time? 3. Base on the graph of concentration against 1/t (Figure 3), describe the relationship between

the reducing of concentration with the rate of reaction? 4. Why we must use the same size of conical flask in each repeating experiment?

ANSWER: 1. We can differentiate the concentration of sodium thiosulphate by diluting the initial solution

with water. The initial concentration of sodium thiosulphate is 0.2 mol dm-3, to get another solution which is less concentrated than 0.2mol dm-3, diluting is done base on the equation 8

Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 M1V1=M2V2. The water needed to diluting the initial concentration is depends on the initial concentration and final concentration needed. 2. To get the rate of reaction at instantaneous time, get the tangent of the graph at that time, then count their gradient. 3. The graph of concentration against 1/time showed 1/time increase linearly with the increasing of concentration. When the concentration of sodium thiosulphate reduce, the time taken for marked ‘X’ disappeared longer than more concentrated solution. So, the rate of reaction for less concentrated is less than more concentrated. 4. We must use the same size of conical flask because area for yellow precipitate must be same. If we use larger connical flask, the time taken for yellow precipitate to cover marked ‘X’ will be longer than expected.

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Muhamad Faris Azmi and Mohd Hamizi Yusoff 2 009 ENHANCE

Figure 4

1. You are given two same liquid but different in concentration. ‘A’ is less concentrated than ‘B’. If the two liquid getting boil at the same temperature, which one of them will boil first? Why? 2. The rate of reaction is the speed with which its reactions disappear and its product form. The speed is measured by the amount of products form. One of the factors that determine the rate of reaction is concentration of the substance. Give other factors that influence the rate of reaction of the chemicals reaction? Answer: 1. Liquid B will boil first because it is more concentrated. A liquid which is more concentrated

has much same molecules per volume. The possibility for molecules to collide each other is greater and the effective collision will form products. So, the time taken for the concentrated solution, B, to reach the products is less than less concentrated solution, A. 2. There are a few factors that influence reaction rates like temperature, the absence of catalyst and the nature of the substance like size of the molecules.

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