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Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
LABORATORY EXERCISE
Kinetics and Chemical Equilibrium Page 1 of 7
Objectives: At the end of this exercise, you are expected to: Make and record observations, measurements and approximations. Interpret and evaluate experimental observations and data.
General Direction. Study the two experimental set-ups. Answer what is asked appropriately.
1. Identical pieces of brass were placed in two different boiling liquids for 12 hours. The graphs show how the mass of each ea ch piece of brass changed.
Graph A Brass in boiling acid solution
Graph B Brass in boiling basic solution
1
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
LABORATORY EXERCISE
Kinetics and Chemical Equilibrium Page 2 of 7
(a) Give one similarity in the change in mass of the brass in both liquids.
(b) Describe two ways in which the loss of mass shown in graph A is different from that shown in graph B.
(c) List three (3) different safety precautions that are needed in doing this investigation.
2
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
Kinetics and Chemical Equilibrium
LABORATORY EXERCISE
Page 3 of 7
2. The rate of reaction between hydrochloric acid (HCl) and aqueous sodium thiosulfate (Na2S2O3 (aq)) was investigated. When these chemicals react they form a precipitate which makes the solution go cloudy. The formation of this precipitate can be used to show how fast the reaction continues.
Five tests were done using the tools shown below.
Test 1 Using a graduated cylinder, 60 cm3 of aqueous sodium thiosulfate was poured into a conical flask. The conical flask was placed on a printed sheet of paper. 10 cm3 of the hydrochloric acid was added to the solution in the conical flask and the stop clock started. The time taken for the printed words to disappear from view was measured.
3
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
LABORATORY EXERCISE
Kinetics and Chemical Equilibrium Page 4 of 7
Test 2 Using a graduated cylinder, 50 cm3 of aqueous sodium thiosulfate was poured into a conical flask, followed by 10 cm3 of distilled water. The conical flask was placed on the printed sheet. 10 cm3 of the hydrochloric acid was added to the solution in the conical flask and the stop clock started. The time taken for the printed words to disappear from view was measured.
Test 3 Test 2 was replicated using 45 cm 3 of aqueous sodium thiosulfate and 25 cm3 of distilled water.
Test 4 Test 2 was replicated using 35 cm3 of aqueous sodium thiosulfate and 15 cm3 of distilled water.
Test 5 Test 2 was replicated using 10 cm 3 of aqueous sodium thiosulfate and 20 cm3 of distilled water.
4
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
LABORATORY EXERCISE
Kinetics and Chemical Equilibrium Page 5 of 7
(a) Use the stop clock diagrams to record the times in the table. Complete the table.
5
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
Kinetics and Chemical Equilibrium
LABORATORY EXERCISE
Page 6 of 7
(b) Plot the results on the grid and draw a smooth line graph.
6
Laboratory Exercise No.
002
Course Code
Description
General Chemistry I
Title of Activity
Kinetics and Chemical Equilibrium
LABORATORY EXERCISE
Page 7 of 7
(c) From your graph, infer the time for the printed words to disappear if Test 2 was repeated using 15 cm3 of aqueous sodium thiosulfate and 15 cm3 of distilled water. Show your solution on how you come up with the answer.
(d) In which test was the rate of reaction greatest? Explain why the rate of reaction was greatest in this test.
