Consider the following intermediate chemical equations:
[tex]$\begin{array}{l}
2 H_2(g)+O_2(g) \rightarrow 2 H_2 O(l) \
H_2(g)+F_2(g) \rightarrow 2 HF(g)
\end{array}$[/tex]
In the final chemical equation, HF and [tex]$O _2$[/tex] are the products that are formed through the reaction between [tex]$H _2 O$[/tex] and [tex]$F _2$[/tex]. Before you can add these intermediate chemical equations, you need to alter them by multiplying the
A. second equation by 2 and reversing the first equation.
B. first equation by 2 and reversing it.
C. first equation by (1 / 2) and reversing the second equation.
D. second equation by 2 and reversing it.
Answer (2)
To achieve the desired reaction of H2O and F2 producing HF and O2, the first equation needs to be reversed, and the second equation multiplied by 2. This results in the balanced reaction. The correct answer is A: multiplying the second equation by 2 and reversing the first equation.
;
Reverse the first equation: 2 H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) becomes 2 H 2 O ( l ) → 2 H 2 ( g ) + O 2 ( g ) .
Multiply the second equation by 2: H 2 ( g ) + F 2 ( g ) → 2 H F ( g ) becomes 2 H 2 ( g ) + 2 F 2 ( g ) → 4 H F ( g ) .
Add the modified equations and simplify by canceling out common terms.
The correct alteration is multiplying the second equation by 2 and reversing the first equation.
Explanation
Understanding the Problem We are given two chemical equations and asked to determine how to manipulate them so that, when added together, they represent the reaction where H 2 O and F 2 react to form H F and O 2 .
Target Reaction The target reaction is: 2 H 2 O + 2 F 2 → 4 H F + O 2 . We need to manipulate the given equations to match this reaction.
Manipulating the First Equation Consider the first equation: 2 H 2 ( g ) + O 2 ( g ) → 2 H 2 O ( l ) . To get 2 H 2 O on the reactant side, we need to reverse the equation: 2 H 2 O ( l ) → 2 H 2 ( g ) + O 2 ( g ) .
Manipulating the Second Equation Consider the second equation: H 2 ( g ) + F 2 ( g ) → 2 H F ( g ) . To get 4 H F on the product side, we need to multiply the equation by 2: 2 H 2 ( g ) + 2 F 2 ( g ) → 4 H F ( g ) .
Adding the Modified Equations Now, add the modified equations: 2 H 2 O ( l ) → 2 H 2 ( g ) + O 2 ( g ) 2 H 2 ( g ) + 2 F 2 ( g ) → 4 H F ( g ) Adding these gives: 2 H 2 O ( l ) + 2 H 2 ( g ) + 2 F 2 ( g ) → 2 H 2 ( g ) + O 2 ( g ) + 4 H F ( g ) .
Simplifying the Result Simplify the equation by cancelling out 2 H 2 ( g ) from both sides: 2 H 2 O ( l ) + 2 F 2 ( g ) → O 2 ( g ) + 4 H F ( g ) . This matches the desired reaction.
Conclusion Therefore, we reversed the first equation and multiplied the second equation by 2. The correct answer is: multiplying the second equation by 2 and reversing the first equation.
Examples
In chemical engineering, balancing equations is crucial for designing industrial processes. For instance, when synthesizing a new material, engineers must ensure that the reaction is stoichiometrically balanced to maximize yield and minimize waste. This involves adjusting the amounts of reactants and products based on the balanced equation, which is achieved by correctly manipulating intermediate equations, similar to the problem we solved.
