We first need to find the number of moles of gas in the container
PV = nRT
where;
P - pressure - 2.87 atm x 101 325 Pa/atm = 290 802.75 Pa
V - volume - 5.29 x 10⁻³ m³
n - number of moles
R - universal gas constant - 8.314 Jmol⁻¹K⁻¹
T - temperature - 230 K
substituting these values in the equation
290 802.75 Pa x 5.29 x 10⁻³ m³ = n x 8.314 Jmol⁻¹K⁻¹ x 230 K
n = 0.804 mol
the molar mass = mass present / number of moles
molar mass of gas = 56.75 g / 0.804 mol
therefore molar mass is 70.6 g/mol
Answer : Option D) The pH of the solution is 8.0.
Explanation : pOH of a solution is a measure of hydroxide ion 
concentration in a particular solution. It gives the measure of alkalinity of a solution. Normally, aqueous solutions at 25°C have pOH which is less than 7 are usually alkaline, when pOH is found to be greater than 7 then they are acidic and when pOH will be equal to 7 then it is neutral.
pH + pOH = 14, this relationship is used to find pH of any unknown solution with given pOH value,
Here, we known pOH is 6.0, so we get,
pH = 14 - 6 = 8.0;
Hence, the pH will be 8.0.
1 mol ------------- 6.02x10²³ atoms
1.14 moles ------ ( atoms )
atoms = 1.14 x ( 6.02x10²³) / 1
atoms = 6.86 x 10²³ / 1
= <span> 6.86 x 10²³ atoms
hope this helps!</span>
