Consider the following reaction. CH3OH(g) CO(g) + 2 H2(g) DELTA-H = +90.7 kJ (a)
ID: 946426 • Letter: C
Question
Consider the following reaction. CH3OH(g) CO(g) + 2 H2(g)
DELTA-H = +90.7 kJ
(a) Is the reaction 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 20.0 kJ, how many grams of hydrogen gas are produced?
_____g
(d) How many kilojoules of heat are released when 11.5 g of CO(g) reacts completely with H2(g) to form CH3OH(g) at constant pressure?
DELTA-H = ___kJ
(e) Calculate DELTA- E when 670.0 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
Explanation / 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) = 127.55 kJ
(c) 20.0 kJ x (2 mol H2 / 90.7 kJ) x (2 g H2 / 1 mol H2) = 0.882 g H2
(d) 11.5 g CO x (1 mol CO / 28 g CO) x (-90.7 kJ / 1 mol CO) = -37.25 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.