Consider the following reaction. (a) Is the reaction exothermic or endothermic?
ID: 810529 • Letter: C
Question
Consider the following reaction.
(a) Is the reaction exothermic or endothermic?
exothermic or endothermic
Consider the following reaction. CH3OH(g) arrow.gif CO(g) + 2 H2(g) delta H = +90.7 kJ (a) Is the reaction exothermic or endothermic? exothermic or endothermic (b) Calculate the amount of heat transferred when 45.0 g of CH3OH(g) are decomposed by this reaction at constant pressure. Delta H = _____________________ kJ (c) If the enthalpy change is 17.0 kJ, how many grams of hydrogen gas are produced? ___________________g (d) How many kilojoules of heat are released when 12.5 g of CO(g) reacts completely with H2(g) to form CH3OH(g) at constant pressure? Delta H = _________________ kJ (e) Calculate delta E when 625.0 g of CH3OH(g) completely reacts at a constant temperature of 300 K and constant pressure of 0.95 atm. R = 8.314 J/mol*K and R = 0.08206 atm*L/mol*K __________________ kJExplanation / Answer
(a) Since the deltaH is positive, it means that the products have more energy than the reactants. This means that the reaction is endothermic.
(b) 45.0 g CH3OH x (1 mol CH3OH / 32 g CH3OH) x (90.7 kJ / 1 mol CH3OH) = 127.5468 kJ
(c) 17.0 kJ x (2 mol H2 / 90.7 kJ) x (2 g H2 / 1 mol H2) = 0.750 g H2
(d) 12.5 g CO x (1 mol CO / 28 g CO) x (-90.7 kJ / 1 mol CO) = -40.491 kJ
Since the value of delta H is the negative for the reverse reaction, we used -90.7 kJ here. The final answer is negative because the reaction gives off heat energy to the surrounding environment.
e) M.W CH3OH = 32 gram
625 gm/32 = 19.53125 mol
PV = nrt
V = nrt /p = 19.53125*0.08206*300/0.95 = 506.1266447 L
1 mol of CH3OH gives 3 mol of products so, final n2 = 625*3/32 =58.59375mol
V2 = 58.59375*0.08206*300/0.95 = 1518.379 L
work done by the system = P2V2- P1V1 = 0.95*( 1518.379- 506.126) = 961.640625 atm.L = 97438.23633 j = 97.4382 KJ
1 atm.L = 101.325 joules
as reaction is endothermic the energy required for this reaction = 90.7*625/32 = 1771.484375KJ
delta E or change in energy = 1771.484375+97.4382 = +1868.9225KJ