Asample of argon gas at stp occupies 56.2 liters. determine the number of moles of argon and the mass in the sample. for the above problem how will you rearrange the ideal gas law to solve for moles of argon?

We can use the ideal gas law equation to find the number of moles;
PV = nRT
where P - pressure
V - volume - 56.2 x 10⁻³ m³
n - number of moles
R - universal gas constant - 8.314 Jmol⁻¹K⁻¹
T - temperature 
standard temperature is 273 K
and standard pressure - 101 325 Pa
we can rearrange the equation to find the number of moles 

substituting the values in the equation 

n = 2.51 mol 
molar mass of Ar - 40 g/mol
mass of Ar in the sample - 2.51 mol x 40 g/mol = 100.4 g

Answerthis solution will not form a precipitateexplanationsolubility equilbrium:         pbf₂(s)  ⇄ pb²⁺(aq) + 2 f⁻(aq)the solubility product expression is    (we exclude solids from the equilibrium expression).now suppose we have the trial ion product q, which we can define as    then, we can interpret  q as the product of the concentration of the ions that we have and ksp as the product of the ion concentrations that are needed to form a saturated solution.if q > ksp, then that implies that there will be a surplus of ions that exceed the amount that is required to form a saturated solution. a precipitate will then form (the precipitate continually  forms until the surplus ions are removed and q is decreased to ksp's value).if q = ksp, the saturated solution that forms is barely saturated and the precipitate will be minimal.if q < ksp, then the ion concentration will not be enough to form a saturated solution (so no precipitate).using our information, we calculate the trial ion product:     since q = 2.7  × 10⁻⁸ < ksp =  4  ×  10⁻⁸, a precipitate will not form.