For these work question\'s, work directly on this exam. For the calculations, sh

Question

For these work question's, work directly on this exam. For the calculations, show all set-ups including numbers and (dimensions). Write your answers with the correct number of significant figures and with proper units. For the calculations, also put a box around your answer. Students should use dimensional analysis to answer the questions. Given the following balanced reaction: 2H_2 S (g) + SO_2 (g) = 3 S (s) + 2 H_2 O (g) How many mL of H_2 S gas, measured at 1 atm pressure and 0 degree C temperature, are needed to produce 0.178 of sulfur? Given the following reactions and their associated enthalpy changes, CO_2 (g) rightarrow C (s) + O_2 (g) delta H = 393.5 kJ C_3 H_8 (g) + 5 O_2 (g) rightarrow 3 CO_2 (g) + 4 H_2 O (g) delta H = -2044 kJ H_2 (g) + 1/2 O_2 (g) rightarrow H_2 O (g) delta H = -241.8 kJ Calculate the enthalpy change for the following reaction: 4H_2 (g) + 3 C (s) rightarrow C_3 H_8 (g)

Explanation / Answer

(1) 2 H2S (g) + SO2 (g) ---------> 3 S (s) + 2 H2O (g)

Mass of Sulphur obtained = 0.178 g.

Molar mass of S = 32 g/mol

Number of moles of S obtained = mass / molar mass = 0.178 / 32 = 0.00556 mol

From the balanced equation,

3 mol of S is obtained from 2 mol of H2S

then, 0.00556 mol of S is obtained from 2 * 0.00556 / 3 = 0.00371 mol of H2S

Assuming ideal behaviour, at STP ( 1atm, 00C)

1 mol of any gas occupies 22414 mL of volume

so, 0.00371 mol of H2S can occupy 0.00371 * 22414 = 82.16 mL of Volume

(2)

do (3) *4 - (1) *3 - (2) * 1 to get the requied equation,

So, deltaH = -241.8 * 3 - 393.5 * 3 - 2044

delta H = - 2499.1 kJ

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