What volume would 8.0g helium gas occupy at 0.0 c and 1.0 atm?

How many moles of gas molecules would you expect to find in a 2.0-L bottle of air at 0.0 C and 1.0 atm?

What would be the mass of gas inside a 3.0-L balloon at 0 C and 1.0 atm filled with

a. He (g) ? b. Co2 (g) ? c. CH4 (g) ?

How many moles of oxygen gas would be present in a 1.0-mL gas sample at 0.0 C and 1.0 atm?

By using the ideal gas formula:

1) TO get the volume: from the ideal gas formula:

when PV = nRT

when we have P = 1 & R = 0.0821 & T = 0°C+273 = 273 K

and n = mass / molar mass of He

= 8 g / 4 g/mol = 2 mol

so by substitution:

1 atm * V = 2 mol * 0.0821 * 273

∴V = 44.8 L

2) To get moles of gas molecules we will use also the ideal gas formula:

PV = nRT

when P = 1 atm & V=2 L & R = 0.0821 & T = 0+273 = 273 K

so by substitution:

1atm * 2 L = n * 0.0821 * 273

∴n (the no. of moles) = 0.089 mol

to get the no. of moles of gas molecules we will multiply by avogadro's number:

= 0.089 * (6.02*10^23) = 5.37X10^22 molecules

3) first we have to get n:

PV = n RT

when P = 1 atm & V = 3L & R = 0.0821 & T = 0+273 = 273 K

so by substitution:

1atm * 3L = n * 0.0821 * 273

∴n the no. of moles of the gas = 0.134 mol

a) when the gas is He so the mass can be calculated from this formula:

He Mass = no. of moles * molar mass of He

= 0.134m * 4g/mol

= 0.5 g

b) when the gas is CO2 So the mass can be calculated from this formula also:

CO2 Mass = no. of moles * molar mass of CO2

=0.134mol * 44 g/mol

= 5.896 g

c) when the gas is CH4 So the mass can be calculated from this formula:

CH4 Mass = no. of moles * molar mass of CH4

= 0.134mol * 16 g / mol

= 2.144 g

4) by using also the ideal gas formula we can get the moles of O2:

PV = nRT

when P = 1 atm & V = 0.001 L & R = 0.0821 & T = 0+273 = 273 K

so by substitution:

1atm * 0.001 L = n * 0.0821 * 273

∴ n = 4.5X10^-5 mol