Q.2.18 P - Chemistry: Molecular Nature Of Matter And Change

Question

State the mass law(s) demonstrated by the following experimental results, and explain your reasoning: 

Experiment 1: A student heats 1.00 g of a blue compound and obtains 0.64 g of a white compound and 0.36 g of a colourless gas. 

Experiment 2: A second student heats 3.25 g of the same blue compound and obtains 2.08 g of a white compound and 1.17 g of a colourless gas.

Step-by-Step Solution

Answer

Individually both experiment 1 and experiment 2 demonstrate the “Law of Conservation of Mass” while collectively they demonstrate the “Law of Definite Composition.”

Step 1: Explanation of Experiment 1

Experiment 1 is given as: 

 $$\begin{gathered} Reactant \left(blue compound\right)=white compound+colorless gas \\ 1g 0.64g 0.36g \end{gathered}$$

 From the equation, we can say that,

 $Mass of reactant\left(1g\right)=Mass of products\left(0.64+0.36=1g\right)$

 As remains constant before and after the reaction hence it demonstrates the “law of Conservation of Mass.”

Step 2: Explanation of Experiment 2

Experiment 2 is given as: 

 $$\begin{gathered} Reactant\left(blue compound\right)=white compound+colorless gas \\ 3.25g 2.08g 1.17g \end{gathered}$$

 From the equation, we can say that,

 $mass of reactant\left(3.25g\right)=mass of products\left(2.08+1.17=3.25g\right)$ 

 As remains constant before and after the reaction hence it demonstrates the “law of Conservation of Mass.”

Step 3: Both Experiments

Both experiments collectively demonstrate the Law of Definite Composition. As the relative amounts of each product are the same in both experiments