2.The given table shows the standard molar enthalpy of formation of some substan

Question

2.The given table shows the standard molar enthalpy of formation of some substances: Substance Delta f Degree (kj/mol) CO2(g) C3118(g) H20(1) (1(3/m01) -94.0 -25.0 -60.0 Find the enthalpy of the following reaction: C3H8(g) + 502(g)right arrow 3CO2(g) +4H20(I) A. 497 kJ B. -215 kJ C. 129 kJ 11 -129 kJ E. -497 kJ 13. How much energy would be needed to heat 450 g of copper metal from a temperature of 25.0 Degree C to a temperature of 75.0 Degree C? The specific heat of copper is 0.385 J/g Degree C. A. 4.33(10^3)j B. 1.30(10^4)J C. 8.66(10^3)3 J D. 19.3k j E. 391 J 14.100.0 mL of 1.0 M NaOH and 100.0 mL of 1.0 M HCI are mixed in a calorimeter. Both solutions are originally at 24.6 Degree C. After the reaction, the final temperature is 31.3 Degree C. Assuming the solution has a density of 1.0g/mL and a specific heat capacity of 4.184 J/g Degree C. calculate the enthalpy change for the reaction as performed. A. 2.8(10^3) kJ B. 2.6(10^4)kJ C. -28 kJ D. 28 kJ E.-5.6 kJ

Explanation / Answer

12 )

C3H8 + 502 ----> 3C02 + 4H20

dH rxn = dHfo products - dHfo reactants

dH rxn = 3 x dHfo C02 + 4 x dHfo H20 - 5 x dHfo 02 - dHfo C3H8

dH rxn = - 3 x 94 - 4 x 60 - 5 x 0 + 25

dH rxn = -497 kJ

so the answer is option E

13)

Heat = m x s x dT

Heat = 450 x 0.385 x ( 75 - 25 )

Heat = 8.66 kJ

so the answer is option C

14)

total volume = 100 + 100 = 200 ml

density = 1 g / ml

so

mass = desnity x volume = 200 x 1

mass = 200 g

so

Heat = m x s x dT

Heat = 200 x 4.184 x ( 31.3 - 24.6 )

Heat = 5.6 kJ

as heat is released it is -5.6 kJ

so the answer is option E

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