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Chapter 5: QCYL (page 227)

Write the heat of formation reaction equations for:

(a) \({{\bf{C}}_{\bf{2}}}{{\bf{H}}_{\bf{5}}}{\bf{O}}{{\bf{C}}_{\bf{2}}}{{\bf{H}}_{\bf{5}}}\)(l)

(b) \({\bf{N}}{{\bf{a}}_{\bf{2}}}{\bf{C}}{{\bf{O}}_{\bf{3}}}\)(s)

Short Answer

Expert verified

(a) \({\rm{\;4C }}\left( {{\rm{s, graphite}}} \right){\rm{ + 5}}{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right){\rm{ + 1/2}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{O}}{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{(l)}}\)

(b) \({\rm{Na}}\left( {\rm{s}} \right){\rm{ + C }}\left( {{\rm{s, graphite}}} \right){\rm{ + 3/2 }}{{\rm{O}}_{\rm{2}}}{\rm{(g) }} \to {\rm{ N}}{{\rm{a}}_{\rm{2}}}{\rm{C}}{{\rm{O}}_{\rm{3}}}{\rm{(s)}}\)

Step by step solution

01

Heat of formation

The heat of formation represented as ΔHf° is used to form one mole of compound from its constituents’ elements under standard conditions.

It provides information on the enthalpy change happening during the formation of compounds.

02

Heat of formation of (a)

\({{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{O}}{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}\)(l)

As the standard state of carbon is graphite, hence

\({\rm{\;4C }}\left( {{\rm{s, graphite}}} \right){\rm{ + 5}}{{\rm{H}}_{\rm{2}}}\left( {\rm{g}} \right){\rm{ + 1/2}}{{\rm{O}}_{\rm{2}}}{\rm{(g)}} \to {{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{O}}{{\rm{C}}_{\rm{2}}}{{\rm{H}}_{\rm{5}}}{\rm{(l)}}\)

03

Heat of formation of (b)

\({\rm{N}}{{\rm{a}}_{\rm{2}}}{\rm{C}}{{\rm{O}}_{\rm{3}}}\)(s)

As the standard state of carbon is graphite, hence

\({\rm{Na}}\left( {\rm{s}} \right){\rm{ + C }}\left( {{\rm{s, graphite}}} \right){\rm{ + 3/2 }}{{\rm{O}}_{\rm{2}}}{\rm{(g) }} \to {\rm{ N}}{{\rm{a}}_{\rm{2}}}{\rm{C}}{{\rm{O}}_{\rm{3}}}{\rm{(s)}}\)

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Most popular questions from this chapter

The white pigment \({\bf{Ti}}{{\bf{O}}_{\bf{2}}}\)is prepared by the reaction of titanium tetrachloride, \({\bf{TiC}}{{\bf{l}}_{\bf{4}}}\), with water vapor in the gas phase:

\({\bf{TiC}}{{\bf{l}}_{\bf{4}}}\left( {\bf{g}} \right){\bf{ + 2}}{{\bf{H}}_{\bf{2}}}{\bf{O}}\left( {\bf{g}} \right) \to {\bf{Ti}}{{\bf{O}}_{\bf{2}}}\left( {\bf{s}} \right){\bf{ + 4HCl}}\left( {\bf{g}} \right)\)

How much heat is evolved in the production of exactly 1 mole of \({\bf{Ti}}{{\bf{O}}_{\bf{2}}}\)(s) under standard state conditions?

Calculate ∆H for the reaction described by the equation. (Hint: use the value for the approximate amount of heat absorbed by the reaction that you calculated in a previous exercise.)

Ba(OH)2. 8H2O(s) + 2NH4SCN(aq) → Ba(SCN)2(aq) + 2NH3(aq) + 10H2O(l)

Water gas, a mixture of \({{\bf{H}}_{\bf{2}}}\) and CO, is an important industrial fuel produced by the reaction of steam with red hot coke, essentially pure carbon:\({\bf{C}}\left( {\bf{s}} \right){\bf{ + }}{{\bf{H}}_{\bf{2}}}{\bf{O}}\left( {\bf{g}} \right) \to {\bf{CO}}\left( {\bf{g}} \right){\bf{ + }}{{\bf{H}}_{\bf{2}}}\left( {\bf{g}} \right)\).

(a) Assuming that coke has the same enthalpy of formation as graphite, calculate \({\bf{\Delta H}}_{{\bf{298}}}^{\bf{0}}\)for this reaction.

(b) Methanol, a liquid fuel that could possibly replace gasoline, can be prepared from water gas and additional hydrogen at high temperature and pressure in the presence of a suitable catalyst:\({\bf{2}}{{\bf{H}}_{\bf{2}}}\left( {\bf{g}} \right){\bf{ + CO}}\left( {\bf{g}} \right) \to {\bf{C}}{{\bf{H}}_{\bf{3}}}{\bf{OH}}\left( {\bf{g}} \right)\).

Under the conditions of the reaction, methanol forms as a gas. Calculate \({\bf{\Delta H}}_{{\bf{298}}}^{\bf{0}}\)for this reaction and for the condensation of gaseous methanol to liquid methanol.

(c) Calculate the heat of combustion of 1 mole of liquid methanol to H2O(g) and CO2(g).

Homes may be heated by pumping hot water through radiators. What mass of water will provide the same amount of heat when cooled from 95.0 to 35.0 °C, as the heat provided when 100 g of steam is cooled from 110 °C to 100°C.

A 45-g aluminum spoon (specific heat 0.88 J/g °C) at 24°C is placed in 180 mL (180 g) of coffee at 85°C and the temperature of the two becomes equal.

(a) What is the final temperature when the two become equal? Assume that coffee has the same specific heat as water.

(b) The first time a student solved this problem she got an answer of 88 °C. Explain why this is clearly an incorrect answer.

Assume that the coffee has the same density and specific heat as water.
See all solutions

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