At room temperature the reaction of iron(III) oxide with carbon to produce solid

Question

At room temperature the reaction of iron(III) oxide with carbon to produce solid metallic iron and carbon monoxide has an equilibrium constant (K) on the order of 10^58 and a positive delta S degree. 2Fe_2O3(s) + 3C(s) rightarrow 4Fe(s) + 3CO_2(g) Despite its very low K at room temperature this reaction is widely used in industry to convert iron oxide into iron metal at very high temperatures. In fact, more than 100000000 tons of iron is made this way annually. Based on this information, what can we infer about this reaction at very high temperatures? A The value of delta H degree must be negative and K increases with increasing temperature. The value of delta H degree must be negative and K decreases with increasing temperature. The value of delta H degree must be positive and K increases with increasing temperature. The value of delta H degree must be positive and K decreases with increasing temperature. Styrene (C_8H_8) is a chemical used in the production of synthetic rubber. When styrene burns in oxygen to form carbon dioxide and liquid water under standard-state conditions at 25 degree C, 42.62 kJ are released per 1 gram of styrene. What is the standard enthalpy of formation of styrene at 25 degree C. -637 kJ/mol -4432 kJ/mol +141 kJ/mol +324 kJ/mol

Explanation / Answer

Despite its very low K at room temperature this reaction is widely used in industry toconvert iron oxide into iron metal at veryhigh temperatures. In fact, more than 1000000tons of iron is made this way annually. Based on this information, what can we inferabout this reaction at very high temperature?

a.The value ofH°must be positive and K increases-------------answer

.b.The value ofH°must be positive and K decrease

.c.The value ofH°must be negative and K increases.

d.The value ofH°must be negative and K decrease.

Go= - RTlnk => K is very small =>

Go should be +

Go= Ho-TSo+ = Ho- hight temp. x positive

Ho should be positiveIncrease temp. =>

K will be increased

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Styrene (C8H8) is a chemical used in the production of synthetic rubber. When styrene burns in oxygen to form carbon dioxide and liquid water under standard-­state conditions at 25°C, 42.62 kJ are released per 1 gram of styrene. What is the standard enthalpy of formation of styrene at 25°C.

Answer = 141 kJ/mol

The reaction you are given is

C8H8 + 10O2 (g) è 8CO2(g) + 4H2O (l)

Hrxn = Hproducts – Hreactants

and

solving for

C8H8.

the enthalpy of reaction (Hrxn) in kJ/mol # moles

in 1 gram = 1g x (1mol/104 g) = 0.0096 moles 42.62 kJ/gram / (0.0096) = 4439 kJ/mol

This is the Hrxn, not the Hformation

enthalpy of formation (Hformation)of styrene using given values

Hrxn = [8HCO2 + 4HH2O] – [10HO2 + 1HC8H8] 4439 = [8(-­393.5) + 4(-­286)] – [10(0) + x],

x = 147 kJ/mol

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