Initial mass of reaction mixture and empty beaker m2
Answers
Answer:
AIM
To verify the law of conservation of mass in a chemical reaction,
MATERIALS REQUIRED
Barium chloride (BaCl2.2H20), sodium sulphate (Na2SO4.10H2O), distilled water, two beakers (100 mL), one beaker (150 mL), physical balance, spring balance (0-500 g), polythene bag, two watch glasses and a glass rod.
THEORY
During a chemical reaction, the mass of the reactants is equal to the mass of the products.
Mass can neither be created nor be destroyed.
It can be demonstrated using a precipitation reaction between BaCl2 (aq) and Na2SO4(aq).
The reaction involved is
CBSE Class 9 Science Practical Skills - Law of Conservation of Mass 1
According to the law of conservation of mass,
Mass of reactants (barium chloride + sodium sulphate) = Mass of products (barium sulphate+ sodium chloride).
PROCEDURE
Pour 50 mL distilled water in two 100 mL beakers.
Using the physical balance, weigh two watch glasses.
Weigh 3.6 g of BaCl2.2H20 in a watch glass of known mass and dissolve it in a beaker containing 50 mL distilled water and label it ‘A’.
Similarly, weigh 8.05 g of Na2SO4.10H2O in another watch glass of known mass and dissolve it in the other beaker containing 50 mL distilled water. Label it ‘B’.
Weigh the 150 mL beaker using spring balance and polythene. Label it ‘C’.
Mix solutions of beaker ‘A’ and ‘B’ together in beaker ‘C’. Mix the contents using a glass rod.
A white precipitate due tc the formation of barium sulphate (BaSO4) appears in the beaker ‘C’.
Weigh the beaker containing the reaction mixture again to find out the mass of products formed.
Compare the masses of the contents before ana after the reaction.
CBSE Class 9 Science Practical Skills - Law of Conservation of Mass 2
OBSERVATIONS
Mass of 50 mL distilled water (assuming density as 1g /cc) = 50.0 g
Mass of BaCl2.H20 = 3.6 g
Mass of BaCl2 solution = 53.6 g
Mass of Na2SO4.10H2O = 8.05 g
Mass of Na2SO4 solution =58.05 g
Total mass of reactants (solutions of BaCl2 and Na2SO4) = 53.6 + 58.05 = 111.65 g
Mass of empty 150 mL beaker,m1 =………………….g
Mass of reaction mixture before precipitation, m2= m1+ 111.65 g = ……………………g
Final mass of reaction mixture after precipitation, m3 =……………………. g
RESULT
On comparing the mass of reactants (m2) with the mass of products (m3), we find m2 equals m3
(within reasonable limits).
This proves the law of conservation of mass.
PRECAUTIONS
Accurate measurement of masses should be ensured.
The spring balance should be held vertical while taking measurements.
Before taking reading, ensure the pointer of the spring balance is at zero mark.
The reading of spring balance should be noted when its pointer comes to rest.
Use small amount of chemicals.
Mix solutions of BaCl2 and Na2SO4 slowly with constant stirring.