HELP PLEASE I HAVE AN EXAM TOMORROW!!!

Question

A foul-smelling gas produced by the reaction of HCl with Na2Swas collected, and a 1.00 L sample was found to have a mass of 1.52 g at STP.

Part A

What is the molecular mass of the gas?

Answer 1

The balanced chemical reaction is:

2HCl (aq) + Na₂S (aq) → 2NaCl (aq) + H₂S (g)

STP

P = 1 atm

T = 0 °C + 273 K = 273 K

V = 1.00 L

R = gas constant = 0.0821 L atm mol^-1 K^-1

mass of gas (g) = 1.52 g

Molar Mass (MM) = ?

Using the ideal gas law equation, PV = nRT, we need to perform some derivations to solve for the molar mass of H₂S.

moles, n = g / MM ... Substitute this equation into the ideal gas law, you get

PV = gRT / MM

Rearrange to solve for MM

MM = gRT / PV

Now plug in the numbers and solve for MM

MM = (1.52 g x 0.0821 L atm mol^-1 K^-1 x 273 K) / (1 atm x 1.00 L)

= 34.06 g/mol ~ 34.1 g/mol (rounded to 3 significant figures)