IDNLearn.com offers a comprehensive solution for all your question and answer needs. Join our community to receive prompt, thorough responses from knowledgeable experts.

Consider the following intermediate chemical equations:

[tex]\[
\begin{array}{ll}
CH_4(g) \rightarrow C(s) + 2H_2(g) & \Delta H_1 = 74.6 \, \text{kJ} \\
CCl_4(g) \rightarrow C(s) + 2Cl_2(g) & \Delta H_2 = 95.7 \, \text{kJ} \\
H_2(g) + Cl_2(g) \rightarrow 2HCl(g) & \Delta H_3 = -92.3 \, \text{kJ}
\end{array}
\][/tex]

What is the enthalpy of the overall chemical reaction [tex]\( CH_4(g) + 4Cl_2(g) \rightarrow CCl_4(g) + 4HCl(g) \)[/tex]?

A. [tex]\(-205.7 \, \text{kJ}\)[/tex]
B. [tex]\(-113.4 \, \text{kJ}\)[/tex]
C. [tex]\(-14.3 \, \text{kJ}\)[/tex]
D. [tex]\(78.0 \, \text{kJ}\)[/tex]


Sagot :

To find the enthalpy change ([tex]\(\Delta H\)[/tex]) for the overall reaction:

[tex]\[ CH_4(g) + 4Cl_2(g) \rightarrow CCl_4(g) + 4HCl(g) \][/tex]

we need to manipulate the given intermediate reactions. Here's a detailed step-by-step solution:

Given intermediate reactions:
1. [tex]\( CH_4(g) \rightarrow C(s) + 2H_2(g) \quad \Delta H_1 = 74.6 \text{ kJ} \)[/tex]
2. [tex]\( CCl_4(g) \rightarrow C(s) + 2Cl_2(g) \quad \Delta H_2 = 95.7 \text{ kJ} \)[/tex]
3. [tex]\( H_2(g) + Cl_2(g) \rightarrow 2HCl(g) \quad \Delta H_3 = -92.3 \text{ kJ} \)[/tex]

We need to construct the overall desired reaction by reversing and combining these intermediate reactions correctly.


1. Reverse the second reaction to match the desired products:
[tex]\[ C(s) + 2Cl_2(g) \rightarrow CCl_4(g) \quad \Delta H = -\Delta H_2 = -95.7 \text{ kJ} \][/tex]

2. Double the third reaction since we need [tex]\(4HCl(g)\)[/tex] in the overall reaction:
[tex]\[ 2H_2(g) + 2Cl_2(g) \rightarrow 4HCl(g) \quad \Delta H = 2 \times \Delta H_3 = 2 \times -92.3 \text{ kJ} = -184.6 \text{ kJ} \][/tex]

3. Now, add up the modified reactions:
[tex]\[ CH_4(g) \rightarrow C(s) + 2H_2(g) \quad \Delta H_1 = 74.6 \text{ kJ} \][/tex]

[tex]\[ C(s) + 2Cl_2(g) \rightarrow CCl_4(g) \quad \Delta H = -95.7 \text{ kJ} \][/tex]

[tex]\[ 2H_2(g) + 2Cl_2(g) \rightarrow 4HCl(g) \quad \Delta H = -184.6 \text{ kJ} \][/tex]

When we add these reactions together, we need to ensure intermediates cancel out correctly to achieve the overall equation:
- [tex]\(C(s)\)[/tex] cancels out.
- [tex]\(2H_2(g)\)[/tex] cancels out.
- [tex]\(2Cl_2(g)\)[/tex] remains:

[tex]\[ CH_4(g) + 4Cl_2(g) \rightarrow CCl_4(g) + 4HCl(g) \][/tex]

Finally, sum the enthalpies:
[tex]\[ \Delta H_{\text{overall}} = \Delta H_1 + (-\Delta H_2) + 2 \times \Delta H_3 \][/tex]
[tex]\[ \Delta H_{\text{overall}} = 74.6 \text{ kJ} + (-95.7 \text{ kJ}) + (-184.6 \text{ kJ}) \][/tex]
[tex]\[ \Delta H_{\text{overall}} = 74.6 - 95.7 - 184.6 \][/tex]
[tex]\[ \Delta H_{\text{overall}} = -205.7 \text{ kJ} \][/tex]

Therefore, the enthalpy change for the overall reaction is [tex]\(-205.7 \text{ kJ}\)[/tex].

The correct answer is:
[tex]\[ -205.7 \text{ kJ} \][/tex]
We appreciate your presence here. Keep sharing knowledge and helping others find the answers they need. This community is the perfect place to learn together. IDNLearn.com provides the best answers to your questions. Thank you for visiting, and come back soon for more helpful information.