7.00g of Compound X with molecular formula C5H10 are burned in a constant-pressure calorimeter containing 35.00kg of water at 25°C. The temperature of the water is observed to rise by 2.113°C. (You may assume all the heat released by the reaction is absorbed by the water, and none by the calorimeter itself.) Calculate the standard heat of formation of Compound X at 25°C. Be sure your answer has a unit symbol, if necessary, and round it to the correct number of significant digits.

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Explanation:

The given data is as follows.

      mass of water = 35.00 kg = 35 × 1000 g = 35000 g

      specific heat of water = 4.186 [tex]J/g ^{0}C[/tex]

      change in temperature = 2.113 [tex]^{0}C[/tex]

Formula to calculate heat change is as follows.

                       q = [tex]m \times C \times \Delta T[/tex]

Putting the given values into the above formula as follows.

                        q = [tex]m \times C \times \Delta T[/tex]

                        q = [tex]35000 g \times 4.186 J/g ^{0}C \times 2.113^{0}C[/tex]

                           = 309131.9 J

or,                        = [tex]\frac{309131.9 J \times 1 kg}{1000 J}[/tex]

                            = 309.1 kJ

As 7.00 g of compound 'X' is giving 309.131 kJ of heat. Therefore, 1 mole of [tex]C_{5}H_{10}[/tex] (molar mass = 70 g) will give the heat as follows.

                      [tex]\frac{309.1}{7} \times 70 kJ/mol[/tex]

                    = 3091 kJ/mol

So, the reaction equation will be as follows.

      [tex]C_{5}H_{10}(g) + \frac{15}{2}O_{2} \rightarrow 5CO_{2}(g) + 5H_{2}O(g)[/tex]    

Value of [tex]\Delta H_{combustion}[/tex] = 3091 kJ/mol for the reaction.

Standard enthalpy values for formation of included atoms or molecules into this reaction are as follows.

       [tex]CO_{2}(g)[/tex] = -393.5 kJ/mol,      [tex]O_{2}(g)[/tex] = 0 kJ/mol

       [tex]H_{2}O(g)[/tex] = -241.8 kJ/mol

Formula to calculate standard heat of formation of compound [tex]C_{5}H_{10}[/tex] is as follows.

          [tex]\Delta H_C_{5}H_{10} = E\Delta H^{0}_f(products) - E\Delta H^{0}_f(reactants)[/tex]

                        = [tex][5 times \Delta H^{0}_f{CO_{2}} + 5 times \Delta H^{0}_f{H_{2}O}] - [5 times \Delta H^{0}_f{C_{5}H_{10}} + \frac{15}{2} \Delta H^{0}_f{O_{2}}[/tex]

              3091 kJ/mol = [tex][(5 times -393.5 kJ/mol) + (5 \times -241.8 kJ/mol)] - [5 times \Delta H^{0}_f{C_{5}H_{10}} + (\frac{15}{2} \times 0)][/tex]

             [tex]-\Delta H^{0}_f{C_{5}H_{10}}[/tex] = -3091 kJ/mol + 1967.5 kJ/mol + 1209 kJ/mol

                                             = 85.5 kJ/mol

or,             [tex]\Delta H^{0}_f{C_{5}H_{10}}[/tex] = -85.5 kJ/mol

Thus, we can conclude that the standard heat of formation of given compound X is -85.5 kJ/mol.

                 -

The standard heat of formation of Compound X at 25°C is -85.5 kJ

Given Here,

mass of water = 35 kg = 35000 g

specific heat of water = 4.186  

change in temperature = 2.113

Specific heat formula,

[tex]\rm \bold {Q = mc \Delta T} \\[/tex]

[tex]\rm \bold {Q = 35000 \times 4.186 \times 4.186 } \\\\\rm \bold {Q = 309131.9 J}\\\\\rm \bold {Q = 309.1 kJ}[/tex]

The molar mass of  C5H10 is 70 g/mole Hence 7 gram of compound produce 3091 kJ/mol energy.

The combustion reaction,

[tex]\rm \bold {C_5H_1_0 \rightarrow \frac{15}{2} CO_2 + 5H_2 O }[/tex]

Standard Enthalpy formula,

[tex]\rm \bold { \Delta H rxn = \sum \Delta H(products ) - \sum \Delta H(reactants) }[/tex]

Put the value, we get

[tex]\rm \bold {\Delta H rxn = -85.5 kJ/mol}\\[/tex]

Hence we can conclude that the standard heat of formation of Compound X at 25°C is -85.5 kJ

To know more about standard heat of formation, refer to the link:

https://brainly.com/question/13096727?referrer=searchResults

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