Activity 1.2 of Chapter 1 Chemical Reactions and Equations helps students understand how two aqueous solutions react to form precipitate. This experiment demonstrates a double displacement reaction and a precipitation reaction, both of which are important concepts in chemistry.
The activity helps students observe the formation of a new substance and understand how ions are exchanged between compounds during a chemical reaction.
Activity 1.2 Solution
Objective
To
observe the chemical reaction between lead nitrate solution and potassium iodide
solution and identify the type of reaction involved.
Material Required
1. Lead nitrate solution
2. Potassium iodide solution
3. Test tubes
Procedure
· Take potassium iodide solution in another test tube.
· Add potassium iodide solution to the lead nitrate solution.
· Observe the mixture carefully for a few minutes.
Observation
A yellow-coloured precipitate of lead
iodide is formed which is a solid insoluble substance and potassium nitrate
remains as solution.
Chemical reaction
Pb (NO3)2 (aq) + 2KI
(aq) → PbI2 (s) +2KNO3(s)
Lead
nitrate Potassium iodide Lead Iodide Potassium nitrate
Yellow ppt.
Explanation
A
double displacement occurs between lead nitrate and potassium iodide. There is
a mutual exchange of ions between these two compounds.
As
a result, a solid insoluble substance lead iodide is formed. This called a
precipitate and the reaction is called precipitation reaction.
Type of Chemical Reactions
i. Double displacement
ii. Precipitate reaction
Conclusion
This
activity demonstrates a double displacement reaction between lead nitrate and
potassium iodide solutions. Due to formation of yellow precipitate of lead
iodide, the reaction is also called precipitation reaction.
Precautions
· Handle chemical solutions carefully.
· Perform the activity under teacher supervision.
· Avoid direct contact of chemical with skin and eyes.
Viva Questions
Q1.
What is precipitate?
Answer
A
precipitate is an insoluble solid formed during a chemical reaction in a solution.
Q2.
What is the chemical name of yellow precipitate formed in this activity?
Answer
Lead iodide
Q3.
What is a double displacement reaction?
Answer
A reaction in which two compounds exchange their
ions to form new compounds is called a double displacement reaction.
Q4.
Why the reaction involved in this activity is called precipitation reaction?
Answer
One
product is a precipitate (insoluble solid) in the reaction, so the reaction precipitation
reaction.
Key Learning Points
· Lead nitrate reacts with potassium iodide to form lead iodide and potassium nitrate.
· A yellow precipitate of lead iodide is formed.
· The reaction is a double displacement reaction.
· The reaction is also a precipitation reaction.
· Formation of a precipitate indicates the formation of a new substance.
Multiple Choice Questions
Q1. What is formed when lead nitrate solution reacts with potassium iodide solution?
a. Potassium chloride
b. Lead oxide
c. Lead iodide
d. Potassium sulphate
Correct
answer - c. Lead iodide
Q2. What is the colour of the precipitate formed in this reaction?
a. White
b. Green
c. Yellow
d. Blue
Correct
answer - c. Yellow
Q3. Which type of reaction occurs in this activity?
a. Combination reaction
b. Decomposition reaction
c. Double displacement reaction
d. Oxidation reaction
Correct
answer - c. Double
displacement reaction
Q4. Why is this reaction called a precipitate reaction?
a. Gas is produced
b. Heat is absorbed
c. An insoluble solid is formed
d. Water is formed
Correct
answer - c. An
insoluble solid is formed
Q5. Which substance remains dissolved in the solution after the reaction?
a. Lead nitrate
b. Potassium nitrate
c. Lead iodide
d. Iodine
Correct
answer - b. Potassium
nitrate
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