Question

ning Chapter Wiktoria Worach - Forest College - CHEM 115 - Fall19 - SHAH/WISER/FISCHER > Activities and Due Dates Chapter 6 < Assignment Score: 100/900 Resources Wint Check Answer 0/100 Question 3 of 9 A gas mixture is made by combining 7.8 g each of Ar, Ne, and an unknown diatomie gas. At STP, the mixture occupies a volume of 99.71 L What is the molar mass of the unknown gas? 100/100 Correct 0/100 g/mol molar mass: 0/100 Identify the unknown gas. 0/100 OH Ос, 0/100 OOO 07100 0/100 0/100

Answer 1

Answer

Molar mass = 2.017g/mol

Unknown gas : H₂

Explanation

Ideal gas equation is

PV = nRT

P = Pressure , 1atm

V = Volume , 99.71L

n = number of moles

R = gas constant , 0.082057(L atm / mol K)

T = Temperature , 273.15K

n = PV /RT

= 1atm × 99.71L / (0.082057(L atm/mol K) × 273.15K)

= 4.449mol

Total number of moles = 4.449mol

moles of Ar = 7.8g / 39.95g/mol = 0.1952mol

moles of Ne = 7.8g/20.18g/mol = 0.3865mol

moles of unknown gas = 4.449mol - ( 0.1952mol + 0.3865mol) = 3.8673mol

molar mass = mass / number of moles

molar mass of unknown gas = 7.8g / 3.8673mol = 2.017g/mol