Question

1) What is the density (in mg/mL) of a H₂S gas at 12.9 atm and 137 K?

2) Calcium carbonate reacts with hydrochloric acid to produce carbon dioxide gas. If 35.3 g of calcium carbonate reacts with 100 mL of 6.00 M HCl, how many liters of carbon dioxide gas will be produced at 745 mmHg and 23.0 °C? (Hint: Limiting Reactant)

CaCO_{3 (s)} + HCl _(aq)  →  CaCl_{2 (aq)} + CO_{2 (g)} + H₂O _(l)   (unbalanced)

Answer 1

1) The ideal gas equation is

PV = nRT , that can be written as PV = (mass/molarmass) RT

or P x molar mass = (mass/volume) RT

P x molar mass = density xRT

Given P = 12.9 atm

T = 137K

molar mass of H2S = 34 g/Mol

R = 0.0821L.atm/mol.K

Substituting density = PM/RT

= 12.9atm x 34g/mol / 0.0821L.atm/k.mol x 137K

= 38.99g/L

= 38.99mg/mL

2) CaCO3 + 2HCl ------------> CaCl2 + CO2 + H2O

35.3/1000=0.353 0.1L x 6=0.6 0 0 - initial moles

To calculate limiting reagent

0.353/1 0.6/2=0.3

Thus HCl is the limiting reagent .

CaCO3 + 2HCl ------------> CaCl2 + CO2 + H2O

35.3/1000=0.353 0.1L x 6=0.6 0 0 - initial moles

0.053 0 0.3 0.3 - after reaction

Thus the moles of CO2 formed = 0.3 mol

P =745mm=745/760 atm

T = 23C =23+273 = 296 K Thus

using idea gas equation PV =nRT

V = nRT/P

= [0.3 x0.0821L.atm/K.mol x 296 K ] / (745/760)atm

= 7.437 L