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Problem: When hydrochloric acid is poured over potassium sulfide, 43.1 mL of hydrogen sulfide gas is produced at a pressure of 754 torr and 25.8 oC.Determine how much potassium sulfide (in grams) reacted.

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We’re being asked to calculate for the mass of potassium sulfide(K2S) that reacted.


Reaction:             2 HCl(aq) + K2S(aq)⟶H2S(g) + 2 KCl(aq)


We’re going to calculate the mass of potassium sulfide using the following steps.

Step 1. Calculate the moles of H2S produced using the ideal gas equation.

PV=nRT

P = pressure, atm
V = volume, L
n = moles, mol
R = gas constant = 0.08206 (L·atm)/(mol·K)
T = temperature, K

Step 2. Calculate the moles of H2S that reacted using mol to mol comparison.
Step 3. Calculate the mass of H2S that reacted using its molar mass.


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Problem Details

When hydrochloric acid is poured over potassium sulfide, 43.1 mL of hydrogen sulfide gas is produced at a pressure of 754 torr and 25.8 oC.

Determine how much potassium sulfide (in grams) reacted.