Compare the total mass of the reactants to the total mass of the products. What choice demonstrates the Law of Conservation of Mass?
[tex]$12 g C + 22 g O_2 \rightarrow 44 g CO_2$[/tex]
[tex]$4 g H_2 + 61 g Cl_2 \rightarrow 75 g HCl$[/tex]
[tex]$23 g Na + 12 g H_2O \rightarrow 40 g NaOH + 1 g H_2$[/tex]
[tex]$10 g H_2 + 46 g N_2 \rightarrow 56 g NH_3$[/tex]
Answer (1)
Calculate the total mass of reactants and products for each reaction.
Compare the total mass of reactants and products.
Identify the reaction where the total mass of reactants equals the total mass of products.
The reaction that demonstrates the Law of Conservation of Mass is: 10 g H 2 + 46 g N 2 → 56 g N H 3 , where the total mass of reactants equals the total mass of products: 56 g = 56 g .
Explanation
Understanding the Law of Conservation of Mass The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction. We need to compare the total mass of the reactants to the total mass of the products for each given chemical reaction to see which one demonstrates this law.
Analyzing the First Reaction For the first reaction, we have: 12 g C + 22 g O 2 → 44 g C O 2 . The total mass of the reactants is 12 g + 22 g = 34 g . The total mass of the products is 44 g . Since 34 g = 44 g , this reaction does not demonstrate the Law of Conservation of Mass.
Analyzing the Second Reaction For the second reaction, we have: 4 g H 2 + 61 g C l 2 → 75 g H Cl . The total mass of the reactants is 4 g + 61 g = 65 g . The total mass of the products is 75 g . Since 65 g = 75 g , this reaction does not demonstrate the Law of Conservation of Mass.
Analyzing the Third Reaction For the third reaction, we have: 23 g N a + 12 g H 2 O → 40 g N a O H + 1 g H 2 . The total mass of the reactants is 23 g + 12 g = 35 g . The total mass of the products is 40 g + 1 g = 41 g . Since 35 g = 41 g , this reaction does not demonstrate the Law of Conservation of Mass.
Analyzing the Fourth Reaction For the fourth reaction, we have: 10 g H 2 + 46 g N 2 → 56 g N H 3 . The total mass of the reactants is 10 g + 46 g = 56 g . The total mass of the products is 56 g . Since 56 g = 56 g , this reaction demonstrates the Law of Conservation of Mass.
Conclusion Therefore, the fourth reaction, 10 g H 2 + 46 g N 2 → 56 g N H 3 , demonstrates the Law of Conservation of Mass because the total mass of the reactants equals the total mass of the products.
Examples
The Law of Conservation of Mass is fundamental in many real-world applications. For example, when designing a closed-system chemical reactor, engineers must ensure that the total mass of the inputs equals the total mass of the outputs to maintain efficiency and prevent dangerous pressure build-ups. In cooking, when baking a cake, the total mass of the ingredients before baking should ideally equal the mass of the baked cake, although some mass might be lost as gases. In environmental science, understanding mass conservation is crucial for tracking pollutants and understanding chemical reactions in ecosystems.
