What choice demonstrates the Law of Conservation of Mass?
A. [tex]$26 g CaO +8 g H _2 O \rightarrow 31 g Ca ( OH )_2$[/tex]
B. [tex]$2 g H _2+16 g O _2 \rightarrow 19 g H _2 O$[/tex]
C. [tex]$74 g Fe ^{+} 32 g O _2 \rightarrow 105 g Fe _2 O _3$[/tex]
D. [tex]$50 g Mg +33 g O _2 \rightarrow 83 g MgO$[/tex]
Answer (1)
Calculate the total mass of reactants for each reaction.
Calculate the total mass of products for each reaction.
Compare the total mass of reactants and products for each reaction.
Identify the reaction where the total mass of reactants equals the total mass of products: 50 g M g + 33 g O 2 → 83 g M g O .
The choice that demonstrates the Law of Conservation of Mass is 50 g M g + 33 g O 2 → 83 g M g O .
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. This means the total mass of the reactants must equal the total mass of the products. We need to check each reaction to see which one obeys this law.
Analyzing Each Reaction Let's analyze each reaction:
Reaction 1: 26 g C a O + 8 g H 2 O → 31 g C a ( O H ) 2 The total mass of the reactants is 26 g + 8 g = 34 g .
The total mass of the product is 31 g .
Since 34 g = 31 g , this reaction does not demonstrate the Law of Conservation of Mass.
Reaction 2: 2 g H 2 + 16 g O 2 → 19 g H 2 O The total mass of the reactants is 2 g + 16 g = 18 g .
The total mass of the product is 19 g .
Since 18 g = 19 g , this reaction does not demonstrate the Law of Conservation of Mass.
Reaction 3: 74 g F e + 32 g O 2 → 105 g F e 2 O 3 The total mass of the reactants is 74 g + 32 g = 106 g .
The total mass of the product is 105 g .
Since 106 g = 105 g , this reaction does not demonstrate the Law of Conservation of Mass.
Reaction 4: 50 g M g + 33 g O 2 → 83 g M g O The total mass of the reactants is 50 g + 33 g = 83 g .
The total mass of the product is 83 g .
Since 83 g = 83 g , this reaction demonstrates the Law of Conservation of Mass.
Conclusion Therefore, the reaction that demonstrates the Law of Conservation of Mass is: 50 g M g + 33 g O 2 → 83 g M g O
Examples
The Law of Conservation of Mass is crucial in many real-world applications. For example, when designing a rocket, engineers need to know exactly how much fuel is required to achieve a certain velocity. By applying the Law of Conservation of Mass, they can accurately calculate the mass of the exhaust gases that will be produced and ensure that the rocket has enough thrust to reach its destination. Similarly, in chemical manufacturing, this law helps to predict the amount of product that can be obtained from a given amount of reactants, optimizing the efficiency and yield of the process. In environmental science, it is used to track pollutants and understand how they transform and disperse in the environment, ensuring effective pollution control and remediation strategies.
