Question

A student runs two experiments with a constant-volume "bomb" calorimeter containing 1500.g of water.

First, a 7.500g tablet of benzoic acid C6H5CO2H is put into the "bomb" and burned completely in an excess of oxygen. (Benzoic acid is known to have a heat of combustion of 26.454 kJ/g.) The temperature of the water is observed to rise from 10.00°C to 36.99°C over a time of 13.0 minutes.

Next, 5.260g of ethanol C2H5OH are put into the "bomb" and similarly completely burned in an excess of oxygen. This time the temperature of the water rises from 10.00°C to 28.03°C.

Use this information, to answer the questions below about this reaction:

C2H5OH(l)+ 3O2(g)→ 2CO2(g)+ 3H2O(g)

a. Is this reaction exothermic, endothermic, or neither?
b. If you said the reaction was exothermic or endothermic, calculate the amount of heat that was released or absorbed by the reaction in the second experiment.
c. Calculate the reaction enthalpy ΔHrxn per mole of CO2

Answer 1

Answer:

See explaination

Explanation:

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Answer 2

Since there has been a rise in the reaction temperature, there has been an exothermic reaction.

The amount of heat energy released in the second step has been -132.54 kJ.

The reaction enthalpy per mole has been -1160.85 kJ/mol.

(a) To determine whether the reaction has been exothermic or endothermic, the heat absorbed or released has been calculated.

Since there has been a rise in the temperature of the solution with the combustion, the reaction has been termed as the exothermic reaction.

(b) Amount of heat released in second experiment:

In the bomb calorimeter:

$\rm q_r_e_a_c_t_i_o_n\;+\;q_b_o_m_b\;+\;q_w_a_t_e_r\;=\;0$

• $\rm q_w_a_t_e_r$ has been given a:

q = mc$\Delta$T

q = 1500 g × 4.184 J/g.$\rm ^\circ C$ × (36.99 - 10$\rm ^\circ C$ )

$\rm q_w_a_t_e_r$ = 169389.24 J.

• $\rm q_b_o_m_b\;$ can be given as:

q = C $\Delta$T

q = c (36.99 - 10$\rm ^\circ C$ )

$\rm q_b_o_m_b\;$ = 26.99 $\rm ^\circ C$ × c

• $\rm q_r_e_a_c_t_i_o_n$ can be given  by:

q = mass × heat of combustion of benzoic acid

q = 7.5 g × 26.454 kJ/g

$\rm q_r_e_a_c_t_i_o_n$ = 198405 J

$\rm q_r_e_a_c_t_i_o_n\;+\;q_b_o_m_b\;+\;q_w_a_t_e_r\;=\;0$

$\rm q_b_o_m_b\;$ = - ($\rm q_r_e_a_c_t_i_o_n\;+\;q_w_a_t_e_r$)

$\rm q_b_o_m_b\;$ = - (198405 J + 169389.24 J )

$\rm q_b_o_m_b\;$ = 29015.76 J.

$\rm q_b_o_m_b\;$ = 26.99 $\rm ^\circ C$ × c

29015.76 J = 26.99 $\rm ^\circ C$ × c

c of bomb = 1075.05 J/$\rm ^\circ C$.

For the second reaction of combustion of ethanol:

$\rm q_r_e_a_c_t_i_o_n\;+\;q_b_o_m_b\;+\;q_w_a_t_e_r\;=\;0$

• $\rm q_w_a_t_e_r$ has been given as:

q = mc$\Delta$T

q = 1500 g × 4.184 J/g.$\rm ^\circ C$ × (28.03 - 10$\rm ^\circ C$ )

$\rm q_w_a_t_e_r$ = 113156.28 J.

• $\rm q_b_o_m_b\;$ can be given as:

q = C $\Delta$T

q = 1075.05 J/$\rm ^\circ C$ × (28.03 - 10$\rm ^\circ C$ )

$\rm q_b_o_m_b\;$ = 19383.15 J

Moles of ethanol = $\rm \dfrac{weight}{molecular\;weight}$

Moles of ethanol = $\rm \dfrac{5.26\;g}{46.07\;g/mol}$

Moles of ethanol = 0.11417 mol.

• $\rm q_r_e_a_c_t_i_o_n$ for ethanol combustion can be given by:

q = moles of ethanol × $\Delta$H of reaction

$\rm q_r_e_a_c_t_i_o_n$ = 0.11417  × $\Delta$H of reaction

$\rm q_r_e_a_c_t_i_o_n\;+\;q_b_o_m_b\;+\;q_w_a_t_e_r\;=\;0$

$\rm q_r_e_a_c_t_i_o_n$ = - ($\rm q_b_o_m_b\;$ + $\rm q_w_a_t_e_r$)

$\rm q_r_e_a_c_t_i_o_n$ = - (19383.15 J +  113156.28 J)

$\rm q_r_e_a_c_t_i_o_n$ = -132539.43 J

$\rm q_r_e_a_c_t_i_o_n$ = -132.54 kJ.

The amount of heat energy released in the second step has been -132.54 kJ.

(c) The  reaction enthalpy per mole can be given as:

$\rm q_r_e_a_c_t_i_o_n$ = 0.11417 mol  × $\Delta$H of reaction

-132.54 kJ = 0.11417 mol  × $\Delta$H of reaction

$\Delta$H of reaction = -1160.85 kJ/mol.

The reaction enthalpy per mole has been -1160.85 kJ/mol.

Since there has been a rise in the reaction temperature, there has been an exothermic reaction.

The amount of heat energy released in the second step has been -132.54 kJ.

The reaction enthalpy per mole has been -1160.85 kJ/mol.

For more information about the reaction in the bomb calorimeter, refer to the link:

https://brainly.com/question/14989357