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The standard enthalpies of formation of ...

The standard enthalpies of formation of `CO_(2)(g)` and HCOOH (l) are `-393.7 kJ"mol"^(-1)` and `-409.2 kJ"mol"^(-1)` respectively. Which of the following statements are correct?

A

`-393.7 kJ "mol"^(-1)` is the enthalpy change for the reaction, `C(s) + O_(2)(g) to CO_(2)(g)`

B

The enthalpy change for the reaction, `CO_(2)(g) + H_(2)(g) to HCOOH(l)`, would be `-15.5 kJ"mol"^(-1)`.

C

The enthalpy change for the reaction, `H_(2)(g) + CO_(2)(g) to H_(2)O(l) + CO(g)`, is `-409.2 kJ"mol"^(-1)`

D

The final temperature achieved is 291.8 K

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The correct Answer is:
To solve the problem, we need to analyze the standard enthalpies of formation for carbon dioxide (CO₂) and formic acid (HCOOH) and determine which statements about these reactions are correct. ### Step-by-Step Solution: 1. **Write the Reactions for Formation:** - For the formation of CO₂: \[ C(s) + O_2(g) \rightarrow CO_2(g) \quad \Delta H_f = -393.7 \, \text{kJ/mol} \] - For the formation of HCOOH: \[ C(s) + H_2(g) + \frac{1}{2}O_2(g) \rightarrow HCOOH(l) \quad \Delta H_f = -409.2 \, \text{kJ/mol} \] 2. **Determine the Enthalpy Change for the Reaction:** - To find the enthalpy change for the reaction: \[ CO_2(g) + H_2(g) \rightarrow HCOOH(l) \] - We can use Hess's law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for the individual steps. - We can rearrange the formation reactions: - Reverse the reaction for CO₂: \[ CO_2(g) \rightarrow C(s) + O_2(g) \quad \Delta H = +393.7 \, \text{kJ/mol} \] - Keep the reaction for HCOOH as is: \[ C(s) + H_2(g) + \frac{1}{2}O_2(g) \rightarrow HCOOH(l) \quad \Delta H = -409.2 \, \text{kJ/mol} \] 3. **Add the Reactions:** - Adding these two reactions: \[ C(s) + H_2(g) + \frac{1}{2}O_2(g) + CO_2(g) \rightarrow HCOOH(l) + C(s) + O_2(g) \] - The \(C(s)\) and \(O_2(g)\) cancel out, leading to: \[ CO_2(g) + H_2(g) \rightarrow HCOOH(l) \] 4. **Calculate the Enthalpy Change:** - The overall enthalpy change for this reaction is: \[ \Delta H = -409.2 \, \text{kJ/mol} + 393.7 \, \text{kJ/mol} = -15.5 \, \text{kJ/mol} \] 5. **Evaluate the Statements:** - **Statement 1:** The enthalpy change for the formation of CO₂ is \(-393.7 \, \text{kJ/mol}\) (Correct). - **Statement 2:** The enthalpy change for the reaction \(CO_2(g) + H_2(g) \rightarrow HCOOH(l)\) is \(-15.5 \, \text{kJ/mol}\) (Correct). - **Statement 3:** The enthalpy change for the reaction \(H_2(g) + CO_2(g) \rightarrow H_2O + CO\) is incorrect as it does not relate to the formation of HCOOH (Incorrect). - **Statement 4:** The statement about the final temperature achieved is nonsensical in this context (Incorrect). ### Conclusion: The correct statements are: - Statement 1 is correct. - Statement 2 is correct. - Statements 3 and 4 are incorrect.

To solve the problem, we need to analyze the standard enthalpies of formation for carbon dioxide (CO₂) and formic acid (HCOOH) and determine which statements about these reactions are correct. ### Step-by-Step Solution: 1. **Write the Reactions for Formation:** - For the formation of CO₂: \[ C(s) + O_2(g) \rightarrow CO_2(g) \quad \Delta H_f = -393.7 \, \text{kJ/mol} ...
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