Ch-4 Question: ple of iron (specific heatt the 451 J gs? °C ,raises its temperat
ID: 706628 • Letter: C
Question
Ch-4 Question: ple of iron (specific heatt the 451 J gs? °C ,raises its temperature from?50C a. 2.41 J b. 1790J c. 564 J d. 1230 e. 0.414J ANSWER: d 51. The standard enthalpies of formation for several substances are given below: CO(g) H20(I) H202(l) C2HsOH(I) -110.5 kJ/mol -285.8 kJ/mol -187.8 kJ/mol -277.7 k.J/mol Co2(g) H20(g) CH3OH(g) C2HsOHg) 23.1 kJ/mol -393.5 kJ/mol -241.8 kJ/mol -200.7 kJ/mol Determine the heat of vaporization for H20 and C2HsOH. a. -44.0 and-42.6 kJ b. 241.8 and-235.1 kJ c.-54.0 and-42.6 kJ d. 241.8 and 325.1 kJ e. 44.0 and 42.6 kJ ANSWER: e 46. Determine the heat of reaction for the process (Use Hess's Law) 2 Fe(s) +3/2 02(g) -Fe203(s) ans: B using the information given below 2 Fe(s) + 6 H20() 2 Fe(OH)3(s)+ 3 H2(g) AH +321.8 kJ AH 285.8 kJ AH +288.6 kJ H2(g)+ 1/2 02(8) -H20) Fe203(s) +3 H20(I) -2 Fe(OH)3(s)Explanation / Answer
Ans 18 : d) 1230 J
The energy (Q) is given as : mass of substance x specific heat x change in temperature
Putting all the values we get :
Q = 50.0 x 0.451 x (79.4 - 25.0)
= 1230 J