If 25.0 grams of Sb2S3 reacts with an excess of hydrochloric acid, how many grams of H2S are formed? What volume does the H2S formed occupy under conditions of STP?

a) 7.57 g

b) 4.97 L

Explanation:

To calculate the moles :

As is the excess reagent, is the limiting reagent and it limits the formation of product.

According to stoichiometry :

1 mole of form = 3 moles of

Thus 0.074 moles of will form =  of

Mass of

According to ideal gas equation:

P = pressure of gas = 1 atm (at STP)

V = Volume of gas = ?

n = number of moles = 0.222

R = gas constant =

T =temperature =

Thus the volume occupied by is 4.97 L

there are two significant figures.