Question

question 9,10

Page 5 of 6 9. Scott collected 6.60 L of methane at 745 torr and 25 °C, which weighed 4.24 a) (2 pts) Convert the pressure to atm. b) (2 pts) Convert the temperature to K. c) (6 pts) Calculate the molar mass of methane. 10. (10 pts) Terrence finds that all gases exhibit virtually the same behavior in response to temperature and pressure changes, no matter what the gaseous compound's formula mass or shape. The physical properties of gases depend on only four variables: pressure (P), volume (V), Kelvin temperature (T), and number of moles (n). All four variables can be changed simultaneously, but experimenting with only two at a time while keeping the other two constant results in some simple but important mathematical descriptions of gas behavior. Fill the blank in the following table that describes the gas laws. Gas law Constant variables Mathematical Description description Boyle's Temperature (T), law Number of moles (n) V = constant XT Pressure (P), Number of moles (n) Gay- Lussac's law As the temperature increases, the pressure increases. V = constant x n Equal volumes of gases at the same pressure and temperature contain the same number of molecules.

Answer 1

given
pressure of methane = 745 torr =0.980263 atm
Temperature T = 25 C = 273 K + 25 = 298 K

volume of gas = 6.60 l
we have gas constant R = 0.0821 latm/mol/k

use gas equation PV= nRT

let us find out number of moles of methane present

n = PV/RT =0.980263 atm*6.60 l/[0.0821 latm/mol/k*298 K]

n= 0.2644 mols

Molar mass = Given mass of methane/number of mols of Methane present
= 4.24 g/0.2644 mols = 16.03 g/mols
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gas law	constant variables	mathematical description	description
Boyles Law	Temperature,number of moles	P = constant/V	As pressure increases volume decreases
Charle's Law	Pressure,number of mols	V= constant*T	As temperature increases volume increases
Gay-Lussac's law	volume ,number of mols	P=constant*T	As temperature increases pressure increases
Avogadro's Law	pressure, temperature	V=constant*n	Equal volume of gases at same pressure and temperature contain same number of molecules

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