Q18P - 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 colour less 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 colour less 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: 

$$\begin{gathered} \mathbf{Reactant}\mathbf{ }\mathbf{(}\mathbf{blue}\mathbf{ }\mathbf{compound}\mathbf{)}\mathbf{=}\mathbf{White}\mathbf{ }\mathbf{compound}\mathbf{+}\mathbf{col}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{less}\mathbf{ }\mathbf{gas} \\ \mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{1}\mathbf{g}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{0}\mathbf{.}\mathbf{64}\mathbf{ }\mathbf{g}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{0}\mathbf{.}\mathbf{36}\mathbf{ }\mathbf{g} \end{gathered}$$ From the equation, we can say that,

$\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{reactant}\mathbf{ }\mathbf{\left(}\mathbf{1}\mathbf{g}\mathbf{\right)}\mathbf{=}\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{products}\mathbf{ }\mathbf{(}\mathbf{0}\mathbf{.}\mathbf{64}\mathbf{+}\mathbf{0}\mathbf{.}\mathbf{36}\mathbf{=}\mathbf{1}\mathbf{g}\mathbf{)}$ 

 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: 

 $$\begin{gathered} \mathbf{Reactant}\mathbf{ }\mathbf{(}\mathbf{blue}\mathbf{ }\mathbf{compound}\mathbf{)}\mathbf{=}\mathbf{White}\mathbf{ }\mathbf{compound}\mathbf{+}\mathbf{col}\mathbf{ }\mathbf{or}\mathbf{ }\mathbf{less}\mathbf{ }\mathbf{gas} \\ \mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{3}\mathbf{.}\mathbf{25}\mathbf{g}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{2}\mathbf{.}\mathbf{08}\mathbf{ }\mathbf{g}\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{ }\mathbf{1}\mathbf{.}\mathbf{17}\mathbf{g} \end{gathered}$$

From the equation, we can say that,

 $\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{reactant}\mathbf{ }\mathbf{(}\mathbf{3}\mathbf{.}\mathbf{25}\mathbf{ }\mathbf{g}\mathbf{)}\mathbf{=}\mathbf{Mass}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{products}\mathbf{(}\mathbf{2}\mathbf{.}\mathbf{08}\mathbf{+}\mathbf{1}\mathbf{.}\mathbf{17}\mathbf{=}\mathbf{3}\mathbf{.}\mathbf{25}\mathbf{ }\mathbf{g}\mathbf{)}$

 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.

$$\begin{gathered} \mathbf{Ratio}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{products}\mathbf{ }\mathbf{in}\mathbf{ }\mathbf{experminet}\mathbf{ }\mathbf{1}\mathbf{=}\frac{\mathbf{0}\mathbf{.}\mathbf{64}}{\mathbf{0}\mathbf{.}\mathbf{36}}\mathbf{=}\mathbf{1}\mathbf{.}\mathbf{78}\mathbf{:}\mathbf{1} \\ \mathbf{Ratio}\mathbf{ }\mathbf{of}\mathbf{ }\mathbf{products}\mathbf{ }\mathbf{in}\mathbf{ }\mathbf{experminet}\mathbf{ }\mathbf{2}\mathbf{=}\frac{\mathbf{2}\mathbf{.}\mathbf{08}}{\mathbf{1}\mathbf{.}\mathbf{17}}\mathbf{=}\mathbf{1}\mathbf{.}\mathbf{78}\mathbf{:}\mathbf{1} \end{gathered}$$